Child development

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Young child playing in squatting position

 

Child development entails the biological, psychological and emotional changes that occur in human beings between birth and the conclusion of adolescence, as the individual progresses from dependency to increasing autonomy. It is a continuous process with a predictable sequence, yet having a unique course for every child. It does not progress at the same rate and each stage is affected by the preceding developmental experiences. Because these developmental changes may be strongly influenced by genetic factors and events during prenatal life, genetics and prenatal development are usually included as part of the study of child development. Related terms include developmental psychology, referring to development throughout the lifespan, and pediatrics, the branch of medicine relating to the care of children. Developmental change may occur as a result of genetically-controlled processes known as maturation, or as a result of environmental factors and learning, but most commonly involves an interaction between the two. It may also occur as a result of human nature and our ability to learn from our environment. 

There are various definitions of periods in a child's development, since each period is a continuum with individual differences regarding start and ending. Some age-related development periods and examples of defined intervals are: newborn (ages 0–4 weeks); infant (ages 4 weeks – 1 year); toddler (ages 1–3 years); preschooler (ages 4–6 years); school-aged child (ages 6–11 years); adolescent (ages 12–19).

Promoting child development through parental training, among other factors, promotes excellent rates of child development. Parents play a large role in a child's life, socialization, and development. Having multiple parents can add stability to the child's life and therefore encourage healthy development. Another influential factor in a child's development is the quality of their care. Child care programs present a critical opportunity for the promotion of child development.

The optimal development of children is considered vital to society and so it is important to understand the social, cognitive, emotional, and educational development of children. Increased research and interest in this field has resulted in new theories and strategies, with specific regard to practice that promotes development within the school system. There are also some theories that seek to describe a sequence of states that compose child development.

Theories

Ecological systems

Also called "development in context" or "human ecology" theory, ecological systems theory, originally formulated by Urie Bronfenbrenner specifies four types of nested environmental systems, with bi-directional influences within and between the systems. The four systems are microsystem, mesosystem, exosystem, and macrosystem. Each system contains roles, norms and rules that can powerfully shape development. Since its publication in 1979, Bronfenbrenner's major statement of this theory, The Ecology of Human Development has had widespread influence on the way psychologists and others approach the study of human beings and their environments. As a result of this influential conceptualization of development, these environments — from the family to economic and political structures — have come to be viewed as part of the life course from childhood through adulthood.

Piaget

Jean Piaget was a Swiss scholar who began his studies in intellectual development in the 1920s. Piaget's first interests were those that dealt with the ways in which animals adapt to their environments and his first scientific article about this subject was published when he was 10 years old. This eventually led him to pursue a Ph.D. in Zoology, which then led him to his second interest in epistemology. Epistemology branches off from philosophy and deals with the origin of knowledge. Piaget believed the origin of knowledge came from Psychology, so he traveled to Paris and began working on the first “standardized intelligence test” at Alfred Binet laboratories; this influenced his career greatly. As he carried out this intelligence testing he began developing a profound interest in the way children's intellectualism works. As a result, he developed his own laboratory and spent years recording children's intellectual growth and attempted to find out how children develop through various stages of thinking. This led to Piaget develop four important stages of cognitive development: sensorimotor stage (birth to age 2), preoperational stage (age 2 to 7), concrete-operational stage (ages 7 to 12), and formal-operational stage (ages 11 to 12, and thereafter). Piaget concluded that adaption to an environment (behaviour) is managed through schemes and adaption occurs through assimilation and accommodation.

Stages

Sensorimotor: (birth to about age 2) 

This is the first stage in Piaget's theory, where infants have the following basic senses: vision, hearing, and motor skills. In this stage, knowledge of the world is limited but is constantly developing due to the child's experiences and interactions. According to Piaget, when an infant reaches about 7–9 months of age they begin to develop what he called object permanence, this means the child now has the ability to understand that objects keep existing even when they cannot be seen. An example of this would be hiding the child's favorite toy under a blanket, although the child cannot physically see it they still know to look under the blanket.

Preoperational: (begins about the time the child starts to talk, about age 2)

During this stage of development, young children begin analyzing their environment using mental symbols. These symbols often include words and images and the child will begin to apply these various symbols in their everyday lives as they come across different objects, events, and situations. However, Piaget's main focus on this stage and the reason why he named it “preoperational” is because children at this point are not able to apply specific cognitive operations, such as mental math. In addition to symbolism, children start to engage in pretend play in which they pretend to be people they are not (teachers, superheroes). In addition, they sometimes use different props to make this pretend play more real. Some deficiencies in this stage of development are that children who are about 3–4 years old often display what is called egocentrism, which means the child is not able to see someone else's point of view, they feel as if every other person is experiencing the same events and feelings that they are experiencing. However, at about 7, thought processes of children are no longer egocentric and are more intuitive, meaning they now think about the way something looks instead of rational thinking.

Concrete: (about first grade to early adolescence)

During this stage, children between the age of 7 and 11 use appropriate logic to develop cognitive operations and begin applying this new thinking to different events they may encounter. Children in this stage incorporate inductive reasoning, which involves drawing conclusions from other observations in order to make a generalization. Unlike the preoperational stage, children can now change and rearrange mental images and symbols to form a logical thought, an example of this is reversibility in which the child now has the ability to reverse an action just by doing the opposite.

Formal operations: (about early adolescence to mid/late adolescence)

The final stage of Piaget's cognitive development defines a child as now having the ability to “think more rationally and systematically about abstract concepts and hypothetical events”. Some positive aspects during this time is that child or adolescent begins forming their identity and begin understanding why people behave the way they behave. However, there are also some negative aspects which include the child or adolescent developing some egocentric thoughts which include the imaginary audience and the personal fable. An imaginary audience is when an adolescent feels that the world is just as concerned and judgemental of anything the adolescent does as they are; an adolescent may feel as if they are “on stage” and everyone is a critic and they are the ones being critiqued. A personal fable is when the adolescent feels that he or she is a unique person and everything they do is unique. They feel as if they are the only ones that have ever experienced what they are experiencing and that they are invincible and nothing bad will happen to them, it will only happen to others.

Vygotsky

Vygotsky was a Russian theorist, who proposed the sociocultural theory. During the 1920s–1930s while Piaget was developing his own theory, Vygotsky was an active scholar and at that time his theory was said to be “recent” because it was translated out of Russian language and began influencing Western thinking. He posited that children learn through hands-on experience, as Piaget suggested. However, unlike Piaget, he claimed that timely and sensitive intervention by adults when a child is on the edge of learning a new task (called the zone of proximal development) could help children learn new tasks. This technique is called "scaffolding," because it builds upon knowledge children already have with new knowledge that adults can help the child learn. An example of this might be when a parent "helps" an infant clap or roll her hands to the pat-a-cake rhyme, until she can clap and roll her hands herself.

Vygotsky was strongly focused on the role of culture in determining the child's pattern of development. He argued that "Every function in the child's cultural development appears twice: first, on the social level, and later, on the individual level; first, between people (interpsychological) and then inside the child (intrapsychological). This applies equally to voluntary attention, to logical memory, and to the formation of concepts. All the higher functions originate as actual relationships between individuals."

Vygotsky felt that development was a process and saw periods of crisis in child development during which there was a qualitative transformation in the child's mental functioning.

Attachment

Attachment theory, originating in the work of John Bowlby and developed by Mary Ainsworth, is a psychological, evolutionary and ethological theory that provides a descriptive and explanatory framework for understanding interpersonal relationships between human beings. Bowlby's observations of close attachments led him to believe that close emotional bonds or “attachments” between an infant and their primary caregiver is an important requirement that is necessary to form “normal social and emotional development”.

Erik Erikson

Erikson, a follower of Freud's, synthesized both Freud's and his own theories to create what is known as the "psychosocial" stages of human development, which span from birth to death, and focuses on "tasks" at each stage that must be accomplished to successfully navigate life's challenges.

Erikson's eight stages consist of the following:

• Trust vs. mistrust (infant)
• Autonomy vs. shame (toddlerhood)
• Initiative vs. guilt (preschooler)
• Industry vs. inferiority (young adolescent)
• Identity vs. role confusion (adolescent)
• Intimacy vs. isolation (young adulthood)
• Generativity vs. stagnation (middle adulthood)
• Ego integrity vs. despair (old age)

Behavioral

John B. Watson’s behaviorism theory forms the foundation of the behavioral model of development 1925. Watson was able to explain the aspects of human psychology through the process of classical conditioning. With this process, Watson believed that all individual differences in behavior were due to different learning experiences. He wrote extensively on child development and conducted research (see Little Albert experiment). This experiment had shown that phobia could be created by classical conditioning. Watson was instrumental in the modification of William James’ stream of consciousness approach to construct a stream of behavior theory. Watson also helped bring a natural science perspective to child psychology by introducing objective research methods based on observable and measurable behavior. Following Watson's lead, B.F. Skinner further extended this model to cover operant conditioning and verbal behavior. Skinner used the operant chamber, or Skinner box, to observe the behavior of small organisms in a controlled situation and proved that organisms' behaviors are influenced by the environment. Furthermore, he used reinforcement and punishment to shape in desired behavior.

Other

In accordance with his view that the sexual drive is a basic human motivation, Sigmund Freud developed a psychosexual theory of human development from infancy onward, divided into five stages. Each stage centered around the gratification of the libido within a particular area, or erogenous zone, of the body. He also argued that as humans develop, they become fixated on different and specific objects through their stages of development. Each stage contains conflict which requires resolution to enable the child to develop.

The use of dynamical systems theory as a framework for the consideration of development began in the early 1990s and has continued into the present century. Dynamic systems theory stresses nonlinear connections (e.g., between earlier and later social assertiveness) and the capacity of a system to reorganize as a phase shift that is stage-like in nature. Another useful concept for developmentalists is the attractor state, a condition (such as teething or stranger anxiety) that helps to determine apparently unrelated behaviors as well as related ones. Dynamic systems theory has been applied extensively to the study of motor development; the theory also has strong associations with some of Bowlby's views about attachment systems. Dynamic systems theory also relates to the concept of the transactional process, a mutually interactive process in which children and parents simultaneously influence each other, producing developmental change in both over time.

The "core knowledge perspective" is an evolutionary theory in child development that proposes "infants begin life with innate, special-purpose knowledge systems referred to as core domains of thought" There are five core domains of thought, each of which is crucial for survival, which simultaneously prepare us to develop key aspects of early cognition; they are: physical, numerical, linguistic, psychological, and biological.

Continuity and discontinuity

Although the identification of developmental milestones is of interest to researchers and to children's caregivers, many aspects of developmental change are continuous and do not display noticeable milestones of change. Continuous developmental changes, like growth in stature, involve fairly gradual and predictable progress toward adult characteristics. When developmental change is discontinuous, however, researchers may identify not only milestones of development, but related age periods often called stages. A stage is a period of time, often associated with a known chronological age range, during which a behavior or physical characteristic is qualitatively different from what it is at other ages. When an age period is referred to as a stage, the term implies not only this qualitative difference, but also a predictable sequence of developmental events, such that each stage is both preceded and followed by specific other periods associated with characteristic behavioral or physical qualities.

Stages of development may overlap or be associated with specific other aspects of development, such as speech or movement. Even within a particular developmental area, transition into a stage may not mean that the previous stage is completely finished. For example, in Erikson's discussion of stages of personality, this theorist suggests that a lifetime is spent in reworking issues that were originally characteristic of a childhood stage. Similarly, the theorist of cognitive development, Piaget, described situations in which children could solve one type of problem using mature thinking skills, but could not accomplish this for less familiar problems, a phenomenon he called horizontal decalage.

Mechanisms

Girl playing in a play ground

Although developmental change runs parallel with chronological age, age itself cannot cause development. The basic mechanisms or causes of developmental change are genetic factors and environmental factors. Genetic factors are responsible for cellular changes like overall growth, changes in proportion of body and brain parts, and the maturation of aspects of function such as vision and dietary needs. Because genes can be "turned off" and "turned on", the individual's initial genotype may change in function over time, giving rise to further developmental change. Environmental factors affecting development may include both diet and disease exposure, as well as social, emotional, and cognitive experiences. However, examination of environmental factors also shows that young human beings can survive within a fairly broad range of environmental experiences.

Rather than acting as independent mechanisms, genetic and environmental factors often interact to cause developmental change. Some aspects of child development are notable for their plasticity, or the extent to which the direction of development is guided by environmental factors as well as initiated by genetic factors. When an aspect of development is strongly affected by early experience, it is said to show a high degree of plasticity; when the genetic make-up is the primary cause of development, plasticity is said to be low. Plasticity may involve guidance by endogenous factors like hormones as well as by exogenous factors like infection.

Child playing with bubbles

 

One kind of environmental guidance of development has been described as experience-dependent plasticity, in which behavior is altered as a result of learning from the environment. Plasticity of this type can occur throughout the lifespan and may involve many kinds of behavior, including some emotional reactions. A second type of plasticity, experience-expectant plasticity, involves the strong effect of specific experiences during limited sensitive periods of development. For example, the coordinated use of the two eyes, and the experience of a single three-dimensional image rather than the two-dimensional images created by light in each eye, depend on experiences with vision during the second half of the first year of life. Experience-expectant plasticity works to fine-tune aspects of development that cannot proceed to optimum outcomes as a result of genetic factors working alone.

In addition to the existence of plasticity in some aspects of development, genetic-environmental correlations may function in several ways to determine the mature characteristics of the individual. Genetic-environmental correlations are circumstances in which genetic factors make certain experiences more likely to occur. For example, in passive genetic-environmental correlation, a child is likely to experience a particular environment because his or her parents' genetic make-up makes them likely to choose or create such an environment. In evocative genetic-environmental correlation, the child's genetically-caused characteristics cause other people to respond in certain ways, providing a different environment than might occur for a genetically-different child; for instance, a child with Down syndrome may be treated more protectively and less challenging than a non-Down child. Finally, an active genetic-environmental correlation is one in which the child chooses experiences that in turn have their effect; for instance, a muscular, active child may choose after-school sports experiences that create increased athletic skills, but perhaps preclude music lessons. In all of these cases, it becomes difficult to know whether child characteristics were shaped by genetic factors, by experiences, or by a combination of the two.

Research issues and methods

1. What develops? What relevant aspects of the individual change over a period of time?
2. What are the rate and speed of development?
3. What are the mechanisms of development – what aspects of experience and heredity cause developmental change?
4. Are there typical individual differences in the relevant developmental changes?
5. Are there population differences in this aspect of development (for example, differences in the development of boys and of girls)?

Empirical research that attempts to answer these questions may follow a number of patterns. Initially, observational research in naturalistic conditions may be needed to develop a narrative describing and defining an aspect of developmental change, such as changes in reflex reactions in the first year. This type of work may be followed by correlational studies, collecting information about chronological age and some type of development such as vocabulary growth; correlational statistics can be used to state change. Such studies examine the characteristics of children at different ages. These methods may involve longitudinal studies, in which a group of children are re-examined on a number of occasions as they get older, or cross-sectional studies, in which groups of children of different ages are tested once and compared with each other, or there may be a combination of these approaches. Some child development studies examine the effects of experience or heredity by comparing characteristics of different groups of children in a necessarily non-randomized design. Other studies can use randomized designs to compare outcomes for groups of children who receive different interventions or educational treatments.

Milestones

Milestones are changes in specific physical and mental abilities (such as walking and understanding language) that mark the end of one developmental period and the beginning of another. For stage theories, milestones indicate a stage transition. Studies of the accomplishment of many developmental tasks have established typical chronological ages associated with developmental milestones. However, there is considerable variation in the achievement of milestones, even between children with developmental trajectories within the typical range. Some milestones are more variable than others; for example, receptive speech indicators do not show much variation among children with typical hearing, but expressive speech milestones can be quite variable.

A common concern in child development is developmental delay involving a delay in an age-specific ability for important developmental milestones. Prevention of and early intervention in developmental delay are significant topics in the study of child development. Developmental delays should be diagnosed by comparison with characteristic variability of a milestone, not with respect to average age at achievement. An example of a milestone would be eye-hand coordination, which includes a child's increasing ability to manipulate objects in a coordinated manner. Increased knowledge of age-specific milestones allows parents and others to keep track of appropriate development.

There is a phenomenal growth or exponential increase of child development from the age of 4 to 15 years old especially during the age of 4 to 7 years old based on the Yamana chart). The Heckman's chart shows that the highest return of investment in education is maximum during the early years (age 1 to 3 years old) and decreases to a plateau during the school-aged years and adolescence. There are various child development tables or charts e.g. the PILES table where PILES stands for Physical, Intellectual, Language, Emotional and Social development aspects.

Aspects

Child development is not a matter of a single topic, but progresses somewhat differently for different aspects of the individual. Here are descriptions of the development of a number of physical and mental characteristics.

Physical growth

Physical growth in stature and weight occurs over the 15–20 years following birth, as the individual changes from the average weight of 3.5 kg and length of 50 cm at full term birth to full adult size. As stature and weight increase, the individual's proportions also change, from the relatively large head and small torso and limbs of the neonate, to the adult's relatively small head and long torso and limbs. The child's pattern of growth is in a head-to-toe direction, or cephalocaudal, and in an inward to outward pattern (center of the body to the peripheral) called proximodistal.

Speed and pattern

The speed of physical growth is rapid in the months after birth, then slows, so birth weight is doubled in the first four months, tripled by age 12 months, but not quadrupled until 24 months. Growth then proceeds at a slow rate until shortly before puberty (between about 9 and 15 years of age), when a period of rapid growth occurs. Growth is not uniform in rate and timing across all body parts. At birth, head size is already relatively near to that of an adult, but the lower parts of the body are much smaller than adult size. In the course of development, then, the head grows relatively little, and torso and limbs undergo a great deal of growth.

Mechanisms of change

Genetic factors play a major role in determining the growth rate, and particularly the changes in proportion characteristic of early human development. However, genetic factors can produce the maximum growth only if environmental conditions are adequate. Poor nutrition and frequent injury and disease can reduce the individual's adult stature, but the best environment cannot cause growth to a greater stature than is determined by heredity.

Individual variation versus disease

Individual differences in height and weight during childhood are considerable. Some of these differences are due to family genetic factors, others to environmental factors, but at some points in development they may be strongly influenced by individual differences in reproductive maturation.

The American Association of Clinical Endocrinologists defines short stature as height more than 2 standard deviations below the mean for age and gender, which corresponds to the shortest 2.3% of individuals. In contrast, failure to thrive is usually defined in terms of weight, and can be evaluated either by a low weight for the child's age, or by a low rate of increase in the weight. A similar term, stunted growth, generally refers to reduced growth rate as a manifestation of malnutrition in early childhood.

Motor

A child learning to walk

 

Abilities for physical movement change through childhood from the largely reflexive (unlearned, involuntary) movement patterns of the young infant to the highly skilled voluntary movements characteristic of later childhood and adolescence.

Definition

"Motor learning refers to the increasing spatial and temporal accuracy of movements with practice". Motor skills can be divided into two categories: first as basic skills necessary for everyday life and secondly, as recreational skills such as skills for employment or certain specialties based on interest.

Speed and pattern

The speed of motor development is rapid in early life, as many of the reflexes of the newborn alter or disappear within the first year, and slows later. Like physical growth, motor development shows predictable patterns of cephalocaudal (head to foot) and proximodistal (torso to extremities) development, with movements at the head and in the more central areas coming under control before those of the lower part of the body or the hands and feet. Types of movement develop in stage-like sequences; for example, locomotion at 6–8 months involves creeping on all fours, then proceeds to pulling to stand, "cruising" while holding on to an object, walking while holding an adult's hand, and finally walking independently. Older children continue the sequence by walking sideways or backward, galloping, hopping, skipping with one foot and walking with the other, and finally skipping. By middle childhood and adolescence, new motor skills are acquired by instruction or observation rather than in a predictable sequence. There are executive functions of the brain (working memory, timing measure of inhibition and switching) which are important to motor skills. Critiques to the order of Executive Functioning leads to Motor Skills, suggesting Motor Skills can support Executive Functioning in the brain.

Mechanisms

The mechanisms involved in motor development involve some genetic components that determine the physical size of body parts at a given age, as well as aspects of muscle and bone strength. The main areas of the brain involved in motor skills are the frontal cortex, parietal cortex and basal ganglia. The dorsolateral frontal cortex is responsible for strategic processing. The parietal cortex is important in controlling perceptual-motor integration and the basal ganglia and supplementary motor cortex are responsible for motor sequences.

According to a study showing the different relationships between limbs of the body and coordination in infants, genetic components have a huge impact on motor development( Piek, Gasson, Barrett, & Case (2002)). Intra-limb correlations, like the strong relationship and distance between hip and knee joints, were studied and proved to affect the way an infant will walk. There are also bigger genetic factors like the tendency to use the left or right side of the body more, predicting the dominant hand early. Sample t-tests proved that there was a significant difference between both sides at 18 weeks for girls and the right side was considered to be more dominant( Piek et al. (2002)). Some factors, like the fact that boys tend to have larger and longer arms are biological constraints that we cannot control, yet have an influence for example, on when an infant will reach sufficiently. Overall, there are sociological factors and genetic factors that influence motor development. 

Nutrition and exercise also determine strength and therefore the ease and accuracy with which a body part can be moved. Flexibility is also affected by nutrition and exercise as well. It has also been shown that the frontal lobe develops posterio-anteriorally (from back to front). This is significant in motor development because the hind portion of the frontal lobe is known to control motor functions. This form of development is known as "Portional Development" and explains why motor functions develop relatively quickly during typical childhood development, while logic, which is controlled by the middle and front portions of the frontal lobe, usually will not develop until late childhood and early adolescence. Opportunities to carry out movements help establish the abilities to flex (move toward the trunk) and extend body parts, both capacities are necessary for good motor ability. Skilled voluntary movements such as passing objects from hand to hand develop as a result of practice and learning. Mastery Climate is a suggested successful learning environment for children to promote motor skills by their own motivation. This promotes participation and active learning in children, which according to Piaget's theory of cognitive development is extremely important in early childhood rule.

Individual differences

Typical individual differences in motor ability are common and depend in part on the child's weight and build. Infants with smaller, slimmer, and more maturely proportionated infants tended to belly crawl and crawl earlier than the infants with larger builds. Infants with more motor experience have been shown to belly crawl and crawl sooner. Not all infants go through the stages of belly crawling. However, those who skip the stage of belly crawling are not as proficient in their ability to crawl on their hands and knees. After the infant period, typical individual differences are strongly affected by opportunities to practice, observe, and be instructed on specific movements. Atypical motor development such as persistent primitive reflexis beyond 4–6 months or delayed walking may be an indication of developmental delays or conditions such as autism, cerebral palsy, or down syndrome . Lower motor coordination results in difficulties with speed accuracy and trade-off in complex tasks.

Children with disabilities

Children with Down syndrome or Developmental coordination disorder are late to reach major motor skills milestones. A few examples of these milestones are sucking, grasping, rolling, sitting up and walking, talking. Children with Down syndrome sometimes have heart problems, frequent ear infections, hypotonia, or undeveloped muscle mass. This syndrome is caused by atypical chromosomal development. Along with Down syndrome, children can also be diagnosed with a learning disability. Learning Disabilities include disabilities in any of the areas related to language, reading, and mathematics. Basic reading skills is the most common learning disability in children, which, like other disabilities, focuses on the difference between a child's academic achievement and his or her apparent capacity to learn.

Population differences

Regardless of the culture a baby is born into, they are born with a few core domains of knowledge. These principals allow him or her to make sense of their environment and learn upon previous experience by using motor skills such as grasping or crawling. There are some population differences in motor development, with girls showing some advantages in small muscle usage, including articulation of sounds with lips and tongue. Ethnic differences in reflex movements of newborn infants have been reported, suggesting that some biological factor is at work. Cultural differences may encourage learning of motor skills like using the left hand only for sanitary purposes and the right hand for all other uses, producing a population difference. Cultural factors are also seen at work in practiced voluntary movements such as the use of the foot to dribble a soccer ball or the hand to dribble a basketball.

Cognitive/intellectual

Cognitive development is primarily concerned with ways in which young children acquire, develop, and use internal mental capabilities such as problem solving, memory, and language.

What develops?

The capacity to learn, remember, and symbolize information, and to solve problems, exists at a simple level in young infants, who can perform cognitive tasks such as discriminating animate and inanimate beings or recognizing small numbers of objects. During childhood, learning and information-processing increase in speed, memory becomes increasingly longer, and symbol use and the capacity for abstraction develop, until a near-adult level is reached by adolescence.

Mechanisms

Cognitive development has genetic and other biological mechanisms, as is seen in the many genetic causes of intellectual disability. Environmental factors including food and nutrition, responsiveness of parents, daily experiences, physical activity and love can influence early brain development of children. However, although it is assumed that brain functions cause cognitive events, it has not been possible to measure specific brain changes and show that they cause cognitive change. Developmental advances in cognition are also related to experience and learning, and this is particularly the case for higher-level abilities like abstraction, which depend to a considerable extent on formal education.

Speed and pattern

The ability to learn temporal patterns in sequenced actions was investigated in elementary-school age children. Temporal learning depends upon a process of integrating timing patterns with action sequences. Children ages 6–13 and young adults performed a serial response time task in which a response and a timing sequence were presented repeatedly in a phase-matched manner, allowing for integrative learning. The degree of integrative learning was measured as the slowing in performance that resulted when phase-shifting the sequences. Learning was similar for the children and adults on average but increased with age for the children. Executive function measured by Wisconsin Card Sorting Test (WCST) performance as well as a measure of response speed also improved with age. Finally, WCST performance and response speed predicted temporal learning. Taken together, the results indicate that temporal learning continues to develop in pre-adolescents and that maturing executive function or processing speed may play an important role in acquiring temporal patterns in sequenced actions and the development of this ability.

Individual differences

There are typical individual differences in the ages at which specific cognitive abilities are achieved, but schooling for children in industrialized countries is based on the assumption that these differences are not large. Atypical delays in cognitive development are problematic for children in cultures that demand advanced cognitive skills for work and for independent living.

Population differences

There are few population differences in cognitive development. Boys and girls show some differences in their skills and preferences, but there is a great deal of overlap between the groups. Differences in cognitive achievement of different ethnic groups appears to result from cultural or other environmental factors.

Social-emotional

Factors

Newborn infants do not seem to experience fear or have preferences for contact with any specific people. In the first few months they only experience happiness, sadness, and anger. A baby's first smile usually occurs between 6 and 10 weeks. It is called a ‘social smile’ because it usually occurs during social interactions. By about 8–12 months, they go through a fairly rapid change and become fearful of perceived threats; they also begin to prefer familiar people and show anxiety and distress when separated from them or approached by strangers.

Separation anxiety is a typical stage of development to an extent. Kicking, screaming, and throwing temper tantrums are perfectly typical symptoms for separation anxiety. Depending on the level of intensity, one may determine whether or not a child has separation anxiety disorder. This is when a child constantly refuses to separate from the parent, but in an intense manner. This can be given special treatment but the parent usually cannot do anything about the situation.

The capacity for empathy and the understanding of social rules begin in the preschool period and continue to develop into adulthood. Middle childhood is characterized by friendships with age-mates, and adolescence by emotions connected with sexuality and the beginnings of romantic love. Anger seems most intense during the toddler and early preschool period and during adolescence.

Speed and pattern

Some aspects of social-emotional development, like empathy, develop gradually, but others, like fearfulness, seem to involve a rather sudden reorganization of the child's experience of emotion. Sexual and romantic emotions develop in connection with physical maturation.

Mechanisms

Genetic factors appear to regulate some social-emotional developments that occur at predictable ages, such as fearfulness, and attachment to familiar people. Experience plays a role in determining which people are familiar, which social rules are obeyed, and how anger is expressed.

Parenting practices have been shown to predict children's emotional intelligence. The objective is to study the time mothers and children spent together in joint activity, the types of activities that they develop when they are together, and the relation that those activities have with the children's trait emotional intelligence. Data was collected for both mothers and children (N = 159) using self-report questionnaires. Correlations between time variables and trait emotional intelligence dimensions were computed using Pearson's Product-Moment Correlation Coefficient. Partial correlations between the same variables controlling for responsive parenting were also computed. The amount of time mothers spent with their children and the quality of their interactions are important in terms of children's trait emotional intelligence, not only because those times of joint activity reflect a more positive parenting, but because they are likely to promote modeling, reinforcement, shared attention, and social cooperation.

Population differences

Population differences may occur in older children, if, for example, they have learned that it is appropriate for boys to express emotion or behave differently from girls, or if customs learned by children of one ethnic group are different from those learned in another. Social and emotional differences between boys and girls of a given age may also be associated with differences in the timing of puberty characteristic of the two sexes.

Gender

Gender identity is how a person perceives themselves as male, female, or a variation of the two. Studies have found that children can identify themselves as belonging to a certain gender as early as two years old, but how gender identity is developed is a current topic of scientific debate. It is believed that several factors work in conjunction with one another to produce an individual's gender, including: neonatal hormones, postnatal socialization, and genetic influences. However, even the timeline for developing gender is under debate. Some believe that gender is malleable until late childhood, while others argue that gender is established early and gender-typed socialization patterns either reinforce or soften the individual's notion of gender. Since most people identify as the gender that is typically associated to their genitalia, studying the impact of these factors is difficult. Evidence suggests that neonatal androgens, male sex hormones produced in the womb during gestation, play an important role. Testosterone in the womb directly codes the brain for either male or female-typical development. This includes both the physical structure of the brain and the characteristics the person expresses because of it. Persons exposed to high levels of testosterone during gestation typically develop a male gender identity while those who are not or those who do not possess the receptors necessary to interact with these hormones typically develop a female gender identity. An individual's genes are also hypnotized to interact with the hormones during gestation and in turn affect gender identity, but the genes responsible for this and their effects have not been precisely documented and evidence is limited. Postnatal, there is debate on whether socialization plays a part in determining gender identity. It is well documented that children actively seek out information on how to properly interact with others based on their gender, but the extent to which these role models, which can include parents, friends, and TV characters, influence gender identity is less clear and no consensus has been reached in the scientific field.

Language and communication

Mechanisms

Language serves the purpose of communication to express oneself through a systematic and traditional use of sounds, signs, or written symbols. There are four subcomponents in which the child must attain in order to acquire language competence. They include phonology, lexicon, morphology and syntax, and pragmatics. These subcomponents of language development are combined to form the components of language, which are sociolinguistics and literacy. Currently, there is no single accepted theory of language acquisition but various explanations of language development have been accumulated.

Components

The four components of language development include:

• Phonology is concerned with the sounds of language. It is the function, behavior, and organization of sounds as linguistic items. Phonology considers what the sounds of language are and what the rules are for combining sounds. Phonological acquisition in children can be measured by accuracy and frequency of production of various vowels and consonants, the acquisition of phonemic contrasts and distinctive features, or by viewing development in regular stages in their own speech sound systems and to characterize systematic strategies they adopt.
• Lexicon is a complex dictionary of words that enables language speakers to use these words in speech production and comprehension. Lexicon is the inventory of a language's morphemes. Morphemes act as minimal meaning-bearing elements or building blocks of something in language that makes sense. For example, in the word "cat", the component "cat" makes sense as does "at", but "at" does not mean the same thing as "cat". In this example, "ca" does not mean anything.
• Morphology is the study of form or forms. It is the mental system involved in word formation or to the branch of linguistics that deals with words, their internal structure and how they are formed.
• Pragmatics is the study of relationships between linguistic forms and the users of those forms. It also incorporates the use of utterance to serve different functions and can be defined as the ability to communicate one's feelings and desires to others.

Children's development of language also includes semantics which is the attachment of meaning to words. This happens in three stages. First, each word means an entire sentence. For example, a young child may say “mama” but the child may mean “Here is Mama”, “Where is Mama?”, or “I see Mama.” In the second stage, words have meaning but do not have complete definitions. This stage occurs around age two or three. Third, around age seven or eight, words have adult-like definitions and their meanings are more complete.

A child learns the syntax of their language when they are able to join words together into sentences and understand multiple-word sentences said by other people. There appear to be six major stages in which a child's acquisition of syntax develops. First, is the use of sentence-like words in which the child communicates using one word with additional vocal and bodily cues. This stage usually occurs between 12 and 18 months of age. Second, between 18 months to two years, there is the modification stage where children communicate relationships by modifying a topic word. The third stage, between two and three years old, involves the child using complete subject-predicate structures to communicate relationships. Fourth, children make changes on basic sentence structure that enables them to communicate more complex relationships. This stage occurs between the ages of two and a half years to four years. The fifth stage of categorization involves children aged three and a half to seven years refining their sentences with more purposeful word choice that reflects their complex system of categorizing word types. Finally, children use structures of language that involve more complicate syntactic relationships between the ages of five years old to ten years old.

Milestones

Infants begin with cooing and soft vowel sounds. Shortly after birth, this system is developed as the infants begin to understand that their noises, or non-verbal communication, lead to a response from their caregiver. This will then progress into babbling around 5 months of age, with infants first babbling consonant and vowel sounds together that may sound like "ma" or "da". At around 8 months of age, babbling increases to include repetition of sounds, such as "da-da" and infants learn the forms for words and which sounds are more likely to follow other sounds. At this stage, much of the child's communication is open to interpretation. For example, if a child says “bah” when they’re in a toy room with their guardian, it is likely to be interpreted as “ball” because the toy is in sight. However, if you were to listen to the same ‘word’ on a recorded tape without knowing the context, one might not be able to figure out what the child was trying to say. A child's receptive language, the understanding of others' speech, has a gradual development beginning at about 6 months. However, expressive language, the production of words, moves rapidly after its beginning at about a year of age, with a "vocabulary explosion" of rapid word acquisition occurring in the middle of the second year. Grammatical rules and word combinations appear at about age two. Between 20 and 28 months, children move from understanding the difference between high and low, hot and cold and begin to change “no” to “wait a minute”, “not now” and “why”. Eventually, they are able to add pronouns to words and combine them to form short sentences. Mastery of vocabulary and grammar continue gradually through the preschool and school years. Adolescents still have smaller vocabularies than adults and experience more difficulty with constructions such as the passive voice.

By age 1, the child is able to say 1–2 words, responds to its name, imitates familiar sounds and can follow simple instructions. Between 1–2 years old, the child uses 5–20 words, is able to say 2-word sentences and is able to express their wishes by saying words like "more" or "up", and they understand the word "no". During 2 and 3 years of age, the child is able to refer to itself as "me", combine nouns and verbs, has a vocabulary of about 450 words, use short sentences, use some simple plurals and is able to answer "where" questions. By age 4, children are able to use sentences of 4–5 words and has a vocabulary of about 1000 words. Children between the ages of 4 and 5 years old are able to use past tense, have a vocabulary of about 1,500 words, and ask questions like "why?" and "who?". By age 6, the child has a vocabulary of 2,600 words, is able to form sentences of 5–6 words and use a variety of different types of sentences. By the age of 5 or 6 years old, the majority of children have mastered the basics of their native language. Infants, 15 month-olds, are initially unable to understand familiar words in their native language pronounced using an unfamiliar accent. This means that a Canadian-English speaking infant cannot recognize familiar words pronounced with an Australian-English accent. This skill develops close to their second birthdays. However, this can be overcome when a highly familiar story is read in the new accent prior to the test, suggesting the essential functions of underlying spoken language is in place before previously thought.

Vocabulary typically grows from about 20 words at 18 months to around 200 words at 21 months. From around 18 months the child starts to combine words into two-word sentences. Typically the adult expands it to clarify meaning. By 24–27 months the child is producing three or four-word sentences using a logical, if not strictly correct, syntax. The theory is that children apply a basic set of rules such as adding 's' for plurals or inventing simpler words out of words too complicated to repeat like "choskit" for chocolate biscuit. Following this there is a rapid appearance of grammatical rules and ordering of sentences. There is often an interest in rhyme, and imaginative play frequently includes conversations. Children's recorded monologues give insight into the development of the process of organizing information into meaningful units.

By three years the child begins to use complex sentences, including relative clauses, although still perfecting various linguistic systems. By five years of age the child's use of language is very similar to that of an adult. From the age of about three children can indicate fantasy or make-believe linguistics, produce coherent personal stories and fictional narrative with beginnings and endings. It is argued that children devise narrative as a way of understanding their own experience and as a medium for communicating their meaning to others. The ability to engage in extended discourse emerges over time from regular conversation with adults and peers. For this, the child needs to learn to combine his perspective with that of others and with outside events and learn to use linguistic indicators to show he is doing this. They also learn to adjust their language depending on to whom they are speaking. Typically by the age of about 9 a child can recount other narratives in addition to their own experiences, from the perspectives of the author, the characters in the story and their own views.

Sequential skill in learning to talk

Child Age in Months	Language Skill
0–3	Vocal play: cry, coo, gurgle, grunt
3–	Babble: undifferentiated sounds
6–10	Babble: canonical/reduplicated syllables
9-	Imitation
8–18	First words
13–15	Expressive jargon, intonational sentences
13–19	10-word vocabulary
14–24	50-word vocabulary
13–27	Single-word stage and a few sentences, two-to-three-word combinations, Articles: a/the, Plural: -s
23–24	Irregular past: went, modal and verb: can/will, 28 to 436-word vocabulary, 93–265 utterances per hour
25–27	Regular past: -ed, Auxiliary “be”: -‘m, -‘s
23–26	Third-person singular: -s, 896 to 1 507-word vocabulary, 1 500 to 1 700 words per hour

Theories

Although the role of adult discourse is important in facilitating the child's learning, there is considerable disagreement among theorists about the extent to which children's early meanings and expressive words arise. Findings about the initial mapping of new words, the ability to decontextualize words, and refine meaning of words are diverse. One hypothesis is known as the syntactic bootstrapping hypothesis which refers to the child's ability to infer meaning from cues, using grammatical information from the structure of sentences. Another is the multi-route model in which it is argued that context-bound words and referential words follow different routes; the first being mapped onto event representations and the latter onto mental representations. In this model, parental input has a critical role but the children ultimately rely on cognitive processing to establish subsequent use of words. However, naturalistic research on language development has indicated that preschoolers' vocabularies are strongly associated with the number of words addressed to them by adults.

There is no single accepted theory of language acquisition. Instead, there are current theories that help to explain theories of language, theories of cognition, and theories of development. They include the generativist theory, social interactionist theory, usage-based theory (Tomasello), connectionist theory, and behaviorist theory (Skinner). Generativist theories refer to Universal Grammar being innate where language experience activates innate knowledge. Social interactionist theories define language as a social phenomenon. This theory states that children acquire language because they want to communicate with others; this theory is heavily based on social-cognitive abilities that drive the language acquisition process. Usage-based theories define language as a set of formulas that emerge from the child's learning abilities in correspondence with its social cognitive interpretation and understanding of the speakers’ intended meanings. Connectionist theories is a pattern-learning procedure and defines language as a system composed of smaller subsystems or patterns of sound or meaning. Behaviorist theories define language as the establishment of positive reinforcement, but is now regarded a theory of historical interest.

Language

Communication can be defined as the exchange and negotiation of information between two or more individuals through verbal and nonverbal symbols, oral and written (or visual) modes, and the production and comprehension processes of communication. According to First International Congress for the Study of Child Language, “the general hypothesis [is that] access to social interaction is a prerequisite to normal language acquisition”. Principles of conversation include two or more people focusing on one topic. All questions in a conversation should be answered, comments should be understood or acknowledged and any form of direction should, in theory, be followed. In the case of young, undeveloped children, these conversations are expected to be basic or redundant. The role of a guardians during developing stages is to convey that conversation is meant to have a purpose, as well as teaching them to recognize the other speaker's emotions. Communicative language is nonverbal and/or verbal, and to achieve communication competence, four components must be met. These four components of communication competence include: grammatical competence (vocabulary knowledge, rules of word sentence formation, etc.), sociolinguistic competence (appropriateness of meanings and grammatical forms in different social contexts), discourse competence (knowledge required to combine forms and meanings), and strategic competence (knowledge of verbal and nonverbal communication strategies). The attainment of communicative competence is an essential part of actual communication.

Language development is viewed as a motive to communication, and the communicative function of language in-turn provides the motive for language development. Jean Piaget uses the term “acted conversations” to explain a child's style of communication that rely more heavily on gestures and body movements, rather than words. Younger children depend on gestures for a direct statement of their message. As they begin to acquire more language, body movements take on a different role and begin to complement the verbal message. These nonverbal bodily movements allow children to express their emotions before they can express them verbally. The child's nonverbal communication of how they’re feeling is seen in babies 0 to 3 months who use wild, jerky movements of the body to show excitement or distress. This develops to more rhythmic movements of the entire body at 3 to 5 months to demonstrate the child's anger or delight. Between 9–12 months of age, children view themselves as joining the communicative world. Before 9–12 months, babies interact with objects and interact with people, but they do not interact with people about objects. This developmental change is the change from primary intersubjectivity (capacity to share oneself with others) to secondary intersubjectivity (capacity to share one's experience), which changes the infant from an unsociable to socially engaging creature. Around 12 months of age a communicative use of gesture is used. This gesture includes communicative pointing where an infant points to request something, or to point to provide information. Another gesture of communication is presented around the age of 10 and 11 months where infants start gaze-following; they look where another person is looking. This joint attention result in changes to their social cognitive skills between the ages of 9 and 15 months as their time is spent increasingly with others. Children's use of non-verbal communicative gestures foretells future language development. The use of non-verbal communication in the form of gestures indicate the child's interest in communication development, and the meanings they choose to convey that are soon revealed through the verbalization of language.

Language acquisition and development contribute to the verbal form of communication. Children originate with a linguistic system where words they learn, are the words used for functional meaning. This instigation of speech has been termed pragmatic bootstrapping. According to this, children view words as a means of social construction, and that words are used to connect the understanding of communicative intentions of the speaker who speaks a new word. Hence, the competence of verbal communication through language is achieved through the attainability of syntax or grammar. Another function of communication through language is pragmatic development. Pragmatic development includes the child's intentions of communication before he/she knows how to express these intentions, and throughout the first few years of life both language and communicative functions develop.

When children acquire language and learn to use language for communicative functions (pragmatics), children also gain knowledge about the participation in conversations and relating to past experiences/events (discourse knowledge), and how to use language appropriately in congruence with their social situation or social group (sociolinguistic knowledge). Within the first two years of life, a child's language ability progresses and conversational skills, such as the mechanics of verbal interaction, develop. Mechanics of verbal interaction include taking turns, initiating topics, repairing miscommunication, and responding to lengthen or sustain dialogue. Conversation is asymmetrical when a child interacts with an adult because the adult is the one to create structure in the conversation, and to build upon the child's contributions. In accordance to the child's developing conversational skills, asymmetrical conversation between adult and child modulate to an equal temperament of conversation. This shift in balance of conversation suggests a narrative discourse development in communication. Ordinarily, the development of communicative competence and the development of language are positively correlated with one another, however, the correlation is not flawless.

Individual differences

Delays in language is the most frequent type of developmental delay. According to demographics 1 out of 5 children will learn to talk or use words later than other children their age. Speech/language delay is three to four times more common in boys than in girls. Some children will also display behavioral problems due to their frustration of not being able to express what they want or need.

Simple speech delays are usually temporary. Most cases are solved on their own or with a little extra attribution from the family. It's the parent's duty to encourage their baby to talk to them with gestures or sounds and for them to spend a great amount of time playing with, reading to, and communicating with their baby. In certain circumstances, parents will have to seek professional help, such as a speech therapist.

It is important to take into considerations that sometimes delays can be a warning sign of more serious conditions that could include auditory processing disorders, hearing loss, developmental verbal dyspraxia, developmental delay in other areas, or even an autism spectrum disorder (ASD).

Environmental causes

There are many environmental causes that are linked to language delays and they include situations such as, the child is having their full attention on other skills, such as walking perfectly, rather than on language. The child may have a twin or a sibling in which their age are relatively close, and may not be receiving the parent's full attention. Another circumstance could be a child that is in a daycare that provides few adults to be able to administer individual attention. Perhaps the most obvious component would be a child that suffers from psychosocial deprivation such as poverty, malnutrition, poor housing, neglect, inadequate linguistic stimulation, or emotional stress.

Neurological causes

Language delay can be caused by a substantial amount of underlying disorders, such as intellectual disability. Intellectual disability takes part for more than 50 percent of language delays. Language delay is usually more rigorous than other developmental delays in intellectually disabled children, and it is usually the first obvious symptom of intellectual disability. Intellectual disability accounts to global language delay, including delayed auditory comprehension and use of gestures. 

Impaired hearing is one of the most common causes of language delay. A child who can not hear or process speech in a clear and consistent manner will have a language delay. Even the most minimum hearing impairment or auditory processing deficit can considerably affect language development. Essentially, the more the severe the impairment, the more serious the language delay. Nevertheless, deaf children that are born to families who use sign language develop infant babble and use a fully expressive sign language at the same pace as hearing children. 

Developmental Dyslexia is a developmental reading disorder that occurs when the brain does not properly recognize and process the graphic symbols chosen by society to represent the sounds of speech. Children with dyslexia may encounter problems in rhyming and separating sounds that compose words. These abilities are essential in learning to read. Early reading skills rely heavily on word recognition. When using an alphabet writing system this involves in having the ability to separate out the sounds in words and be able to match them with letter and groups of letters. Because they have trouble in connecting sounds of language to the letter of words, this may result difficulty in understanding sentences. They have confusion in mistaking letters such as "b" and "d". For the most part, symptoms of dyslexia may include, difficulty in determining the meaning of a simple sentence, learning to recognize written words, and difficulty in rhyming. 

Autism and speech delay are usually correlated. Problems with verbal language are the most common signs seen in autism. Early diagnosis and treatment of autism can significantly help the child improve their speech skills. Autism is recognized as one of the five pervasive developmental disorders, distinguished by problems with language, speech, communication and social skills that present in early childhood. Some common autistic syndromes are the following, being limited to no verbal speech, echolalia or repeating words out of context, problems responding to verbal instruction and may ignore others who speak directly.

Risk factors

Malnutrition, maternal depression and maternal substance abuse are three of these factors which have received particular attention by researchers, however, many more factors have been considered.

Postnatal depression

Although there are a large number of studies contemplating the effect of maternal depression and postnatal depression of various areas of infant development, they are yet to come to a consensus regarding the true effects. There are numerous studies indicating impaired development, and equally, there are many proclaiming no effect of depression on development. A study of 18-month-olds whose mothers suffered depressive symptoms while they were 6 weeks and/or 6 months old indicated that maternal depression had no effect on the child's cognitive development at 18 months. Furthermore, the study indicates that maternal depression combined with a poor home environment is more likely to have an effect on cognitive development. However, the authors conclude that it may be that short term depression has no effect, where as long term depression could cause more serious problems. A further longitudinal study spanning 7 years again indicate no effect of maternal depression on cognitive development as a whole, however it found a gender difference in that boys are more susceptible to cognitive developmental issues when their mothers suffer depression. This thread is continued in a study of children up to 2 years old. The study reveals a significant difference on cognitive development between genders, with girls having a higher score, however this pattern is found regardless of the child's mother's history of depression. Infants with chronically depressed mothers showed significantly lower scores on the motor and mental scales within the Bayley Scales of Infant Development, contrasting with many older studies. A similar effect has been found at 11 years: male children of depressed mothers score an average of 19.4 points lower on an Intelligence Quotient IQ test than those with healthy mothers, although this difference is much lower in girls. 3 month olds with depressed mothers show significantly lower scores on the Griffiths Mental Development Scale, which covers a range of developmental areas including cognitive, motor and social development. It has been suggested that interactions between depressed mothers and their children may affect social and cognitive abilities in later life. Maternal depression has been shown to influence the mothers’ interaction with her child. When communicating with their child, depressed mothers fail to make changes to their vocal behavior, and tend use unstructured vocal behaviors. Furthermore, when infants interact with depressed mothers they show signs of stress, such as increased pulse and raised cortisol levels, and make more use of avoidance behaviors, for example looking away, compared to those interacting with healthy mothers. The effect of mother-infant interaction at 2 months has been shown to affect the child's cognitive performance at 5 years. Recent studies have begun to identify that other forms of psychopathology that may or may not be co-morbidly occurring with maternal depression can independently influence infants' and toddlers' subsequent social-emotional development through effects on regulatory processes within the child-parent attachment. Maternal interpersonal violence-related post-traumatic stress disorder (PTSD), for example, has been associated with subsequent dysregulation of emotion and aggression by ages 4–7 years.

Maternal drug abuse

Cocaine

Research has provided conflicting evidence regarding the effect of maternal substance abuse during and after pregnancy on children's development. Children exposed to cocaine weigh less than those not exposed at numerous ages ranging from 6 to 30 months. Furthermore, studies indicate that the head circumference of children exposed to cocaine is lower than those unexposed. On the other hand, two more recent studies found no significant differences between those exposed to cocaine and those who were not in either measure. Maternal cocaine use may also affect the child's cognitive development, with exposed children achieving lower scores on measures of psychomotor and mental development. However, again there is conflicting evidence, and a number of studies indicate no effect of maternal cocaine use on their child's cognitive development. Motor development can be impaired by maternal cocaine abuse. As is the case for cognitive and physical development, there are also studies showing no effect of cocaine use on motor development.

Other

The use of cocaine by pregnant women is not the only drug that can have a negative effect on the fetus. Tobacco, marijuana, and opiates are also the types of drugs that can effect an unborn child's cognitive and behavioral development. Smoking tobacco increases pregnancy complications including low birth rate, prematurity, placental abruption, and intrauterine death. It can also cause disturbed maternal-infant interaction; reduced IQ, ADHD, and it can especially cause tobacco use in the child. Parental marijuana exposure may have long-term emotional and behavioral consequences. A ten-year-old child who had been exposed to the drug during pregnancy reported more depressive symptoms than fetuses unexposed. Some short-term effects include executive function impairment, reading difficulty, and delayed state regulation. An opiate drug, such as heroin, decreases birth weight, birth length, and head circumference when exposed to the fetus. Parental opiate exposure has greater conflicting impact than parental cocaine exposure on the infant's Central Nervous System and autonomic nervous system. There are also some negative consequences on a child that you wouldn’t think of with opiates, such as: less rhythmic swallowing, strabismus, and feelings of rejection.

Malnutrition

Poor nutrition early in life contributes to stunting, and by the age of two or three can be associated with cognitive deficits, poor school achievement, and poor social relationships later in life Malnutrition is a large problem in developing nations, and has an important effect on young children's weight and height.Children suffering malnutrition in Colombia weighed less than those living in upper class conditions at the age of 36 months (11.88 kg compared to 14 kg), similarly, malnourished children were shorter than well-nourished children, again at 36 months (85.3 cm in malnourished children; 94 cm in well-nourished children  Malnutrition has been indicated as a negative influence on childhood Intelligence Quotient IQ. Although it is now suggested that this effect is nullified when parental IQ is considered, implying that this difference is genetic.

Nutrients

The effect of low iron levels on cognitive development and IQ is a subject still to reach consensus. Some evidence suggests that well-nourished children with lower levels of iron and folate (although not at such a level to be considered deficient) have a lower IQ than those with higher levels of iron and folate. Furthermore, anaemic children perform worse on cognitive measures than non-anaemic children. These nutrients have been strongly implicated in brain development, along with iodine and zinc. Iodine is required for the generation of thyroid hormones necessary for brain development. Iodine deficiency may reduce IQ by an average of 13.5 points compared to healthy individual. Zinc deficiency has also been shown to slow childhood growth and development.

Socioeconomic status

Socioeconomic status is measured primarily based on the factors of income, educational attainment and occupation. Current investigations into the role of socioeconomic factors on child development repeatedly show that continual poverty is more harmful on Intelligence Quotient IQ, and cognitive abilities than short-lived poverty. Children in families who experience persistent financial hardships and poverty have significantly impaired cognitive abilities compared to those in families who do not face this issue. Low income poverty can cause a number of further issues shown to effect child development, such as poor academic success, less family involvement, iron deficiency, infections, a lack of stimulation, malnutrition and lead poisoning due to lead paint found on the walls of some houses. Child blood levels of lead increase as income decreases. Income poverty is associated with a 6–13 point reduction in IQ for those earning half of the poverty threshold compared to those earning twice the poverty threshold. That being said, children coming from households featuring continual or temporary poverty still perform lower than children in middle-class families.

Parental educational attainment is the most significant socioeconomic factor in predicting the child's cognitive abilities, those with a mother with high IQ are likely to have higher IQs themselves. Similarly, maternal occupation is associated with better cognitive achievement. Those whose mothers’ job entails problem-solving are more likely to be given stimulating tasks and games, and are likely to achieve more advanced verbal competency.

Mother's employment is associated with slightly lower test scores, regardless of socioeconomic status. However, those whose working mother is of a higher socioeconomic status experience more disadvantages because they are being removed from a more enriching environment than a child care. Obviously, the quality of child care is a factor to be considered. Low income children tend to be cared for by grandparents or extended family and therefore form strong bonds with family. High income children tend to be cared for in a child care setting or in home care such as a nanny. If the mother is highly educated, this can be a disadvantage to the child. Even with quality of care controlled for, studies still found a negative correlation between full-time work within the first year and child development. Children whose mothers work are also less likely to receive regular well-baby doctor visits and less likely to be breastfed, which has been proven to improve developmental factors. Effects are felt more strongly when women resume full-time work within the first year of the child's life. These effects may be due in part to pre-existing differences between mothers who return to work and those who do not such as differences in character or reason for returning to work.

Low-income families are less likely to provide a stimulating home learning environment to their children due to time constraints and financial stress. Compared to two-parent households, children with a single-parent generally don't have better social, behavioral, educational, or cognitive outcomes than those with two parents because of economic vulnerability and a lack of parental involvement. A child's academic achievement is influenced by parents' educational attainment, parenting style, and parental investment in their child's cognitive and educational success. Upper-income families are able to afford learning opportunities inside and outside of the classroom. Poverty-stricken children are subjected to fewer stimulating recreational activities, often missing out on trips to libraries or museums, and are unable to access a tutor to help with problematic academic areas.

A further factor in a child's educational attainment involves the school environment, more specifically teacher expectations and attitudes. It has been argued that teachers perceive low-SES children as being less academically able and as such provide them with less attention and reinforcement. On the other hand, it has been found that when schools make an effort to increases family and school involvement, children perform better on state tests.

Parasites

Diarrhea caused by the parasitic disease Giardiasis is associated with lower IQ. Parasitic worms (helminths) are associated with nutritional deficiencies that are known to be a risk to child development. In particular, intestinal parasitism being one of the most neglected tropical diseases in the developed world. Harboring of this parasite could adverse several health implications in children affecting childhood development and morbidity. Reducing the prevalence of the parasite can be a benefit in child growth, development, and educational outcome.

Poisoning

High levels of lead in the blood is associated with attention deficits, while arsenic poisoning has a negative effect on verbal and full Intelligence Quotient IQ. Manganese poisoning due to levels in drinking water is also associated with a reduced IQ of 6.2 points between the highest and lowest level of poisoning. Prenatal exposure to various pesticides including organophosphates, and chlorpyrifos has also been linked to reduced IQ score. Organophosphates have been specifically linked to poorer working memory, verbal comprehension, perceptual reasoning and processing speed.

Other

Cognitive development is related to childhood exposure to violence and trauma, including spousal abuse between the parents and sexual abuse. Intrauterine growth retardation is associated with learning deficits in childhood, and as such, is related to lower IQ.

Neglect

When a child is unable to meet their developmental goals, because they have not been provided with the correct amount of care, stimulation or nutrition this situation is commonly referred to as child neglect. It is the most widespread form of child abuse. Neglect accounted for 78% of all child abuse cases in the United States in 2010 alone. Scientific Studies show that exposure to child neglect can have lifelong consequences for children.

Assessing and identifying

Assessing and identifying neglect pose a number of challenges for practitioners. Given that neglect is a dynamic between the child's development and levels of nurturance, the question in identifying neglect, becomes one of where do you start, with the child's development or with the levels of nurturance?

Development focused methods

Some professionals identify neglect by measuring the developmental levels of a child, for if those developmental levels are normal, one can, by definition, conclude that a child is not being neglected. Areas of development that could be measured include weight, height, stamina, social & emotional responses, speech and motor development. All these features go up to make a medical assessment of whether a child is thriving, so that a professional looking to start an assessment of neglect, might reasonably start with information collected by a doctor. Infants are often weighed and measured when seen by their physicians for well-baby check-ups. The physician initiates a more complete evaluation when the infant's development and functioning are found to be delayed. What this suggests is that social work staff could consult medical notes to establish if the baby or child is failing to thrive, as a first step in a pathway towards identifying neglect. If developmental levels are subnormal, then the identification of neglect then requires the professional establish if those subnormal levels of development can be put down to the level of nurturance experienced by the child. One needs to discount that the developmental delay was caused by some genetic condition or disease, which do not have their basis in a lack of nurturance.

Starting the assessment

Another way of starting a process for identifying neglect is to identify if the child in question is experiencing a level of nurturance lower than that considered necessary to support normal development. In part this requires a knowledge of the level of nurturance required by the child to sustain normal development, which might be particular to his or her age, gender and other factors. However quite how one ascertains what a particular child needs, without referring back to their level of development, is not something theory and policy on neglect is clear about. Furthermore, ascertaining whether a child is getting the requisite level of nurturance needs to take into account not just the intensity of the nurturance, but also, given that the intensity of certain forms of nurturance can vary across time, the duration and frequency of the nurturance. It is acceptable for a child to experience varying and low levels of certain types of nurturance across a day and from time to time, however, the levels of nurturance should never cross thresholds of intensity, duration and frequency. For this reason, professionals are minded to keep detailed histories of care provision, which demonstrate the duration to which the child is exposed to periods of subnormal exposure to care, stimulation, and nutrition.

Starting the assessment

It is most common for guidance to suggest professionals should focus on the levels of nurturance provided by the carers of the child, where neglect is understood as an issue of the parents' behaviour towards the child. Some authors feel that establishing the failure of parents and caregivers to provide care would be sufficient to conclude that neglect was occurring. Action for Children state that, "A child experiences neglect when the adults who look after them fail to meet their needs" clearly defining neglect as a matter of parental performance. This raises the question about what level of nurturance, a carer or parent needs to fall under, to provoke developmental delay, and how one goes about measuring that accurately. 

The method, which focuses on the stimulation provided by the carer, can be subject to critique. Neglect is about the child's development being adversely affected by the levels of nurturance, but the carers' provision of nurturance is not always a good indicator of the level of nurturance received by the child. Neglect may be occurring at school, outside of parental care. The child may be receiving nurturance from siblings or through a boarding school education, which compensates for the lack of nurturance provided by the parents.

Linking to stimulation

Neglect is a process whereby children experience developmental delay owing to experiencing insufficient levels of nurturance. It has been argued that in principle, this means that when starting an assessment of neglect by identifying developmental delay one needs to then check the levels of nurturance received by the child. Certainly, where guidance on identifying neglect does urge for practitioners to measure developmental levels, some guidance urges practitioners to focus on how developmental levels can be attributed to parental behaviour. However, the narrow focus on parental behaviour can be criticised for unnecessarily ruling out the possible effect of institutionalised neglect, e.g. neglect at school. 

If one starts by concluding that the levels of nurture received by the child are insufficient, one then needs to consider the developmental levels achieved by the child.

Further challenges arise, however. Even when one has established developmental delay and exposure to low levels of nurture, one needs to rule out the possibility that the link between the two is coincidental. The developmental delay may be caused by a genetic disorder, disease or physical, sexual or emotional abuse. Of course, the developmental delay may be caused by a mixture of underexposure to nurture, abuse, genetics and disease.

Practical tools for measuring

The Graded Care Profile Tool is a practice tool which gives an objective measure of the quality of care in terms of a parent/carer's commitment. It was developed in the UK.

The North Carolina Family Assessment Scale is a tool which can be used by a practitioner to explore whether neglect is taking place across a range of family functioning areas.

Intervention programs for addressing

Early intervention programs and treatments in developed countries include individual counseling, family, group counseling and social support services, behavioral skills training programs to eliminate problematic behavior and teach parents "appropriate" parenting behavior.

Parenting programs

Video interaction guidance is a video feedback intervention through which a "guider" helps a client to enhance communication within relationships. The client is guided to analyse and reflect on video clips of their own interactions. Video Interaction Guidance has been used where concerns have been expressed over possible parental neglect in cases where the focus child is aged 2–12, and where the child is not the subject of a child protection plan.

The SafeCare program is a preventative program working with parents of children under 6 years old who are at risk of experiencing significant harm through neglect. The program is delivered in the home by trained practitioners, over 18 to 20 sessions and focuses on 3 key areas: parent-infant/child interaction; home safety and child health.

Triple P (Parenting Program) is a positive parenting program. It is a multilevel, parenting and family support strategy. The idea behind it is that if parents are educated on "proper" parenting and given the appropriate resources, it could help decrease the amount of child neglect cases. When deciding whether to leave a child home alone, caregivers need to consider the child's physical, mental, and emotional well-being, as well as state laws and policies regarding this issue.

Evolutionary developmental psychology

From Wikipedia, the free encyclopedia

Evolutionary developmental psychology (EDP) is a research paradigm that applies the basic principles of Darwinian evolution, particularly natural selection, to understand the development of human behavior and cognition. It involves the study of both the genetic and environmental mechanisms that underlie the development of social and cognitive competencies, as well as the epigenetic (gene-environment interactions) processes that adapt these competencies to local conditions.

 

EDP considers both the reliably developing, species-typical features of ontogeny (developmental adaptations), as well as individual differences in behavior, from an evolutionary perspective. While evolutionary views tend to regard most individual differences as the result of either random genetic noise (evolutionary byproducts) and/or idiosyncrasies (for example, peer groups, education, neighborhoods, and chance encounters) rather than products of natural selection, EDP asserts that natural selection can favor the emergence of individual differences via "adaptive developmental plasticity." From this perspective, human development follows alternative life-history strategies in response to environmental variability, rather than following one species-typical pattern of development.

EDP is closely linked to the theoretical framework of evolutionary psychology (EP), but is also distinct from EP in several domains, including research emphasis (EDP focuses on adaptations of ontogeny, as opposed to adaptations of adulthood) and consideration of proximate ontogenetic and environmental factors (i.e., how development happens) in addition to more ultimate factors (i.e., why development happens), which are the focus of mainstream evolutionary psychology.

History

Development and evolution

Like mainstream evolutionary psychology, EDP is rooted in Charles Darwin's theory of natural selection. Darwin himself emphasized development, using the process of embryology as evidence to support his theory. From The Descent of Man:

Man is developed from an ovule...which differs in no respect from the ovules of other animals. The embryo itself at a very early period can hardly be distinguished from that of other members of the vertebrate kingdom.

Darwin also published his observations of the development of one of his own sons in 1877, noting the child's emotional, moral, and linguistic development.

Despite this early emphasis on developmental processes, theories of evolution and theories of development have long been viewed as separate, or even opposed to one another (for additional background, see nature versus nurture). Since the advent of the modern evolutionary synthesis, evolutionary theory has been primarily "gene-centric", and developmental processes have often been seen as incidental. Evolutionary biologist Richard Dawkins's appraisal of development in 1973 illustrates this shift: "The details of embryological developmental processes, interesting as they may be, are irrelevant to evolutionary considerations." Similarly, sociobiologist E. O. Wilson regarded ontogenetic variation as "developmental noise".

As a consequence of this shift in perspective, many biologists interested in topics such as embryology and developmental systems subsequently branched off into evolutionary developmental biology.

Evolutionary perspectives in developmental psychology

Despite the minimization of development in evolutionary theory, early developmental psychology was influenced by evolution. Both Darwin's theory of evolution and Karl Ernst von Baer's developmental principles of ontogeny shaped early thought in developmental psychology. Wilhelm T. Preyer, a pioneer of child psychology, was heavily inspired by Darwin's work and approached the mental development of children from an evolutionary perspective.

However, evolutionary theory has had a limited impact on developmental psychology as a whole, and some authors argue that even its early influence was minimal. Developmental psychology, as with the social sciences in general, has long been resistant to evolutionary theories of development (with some notable exceptions, such as John Bowlby's work on attachment theory). Evolutionary approaches to human behavior were, and to some extent continue to be, considered a form of genetic determinism and dismissive of the role of culture and experience in shaping human behavior (see Standard social science model).

One group of developmental psychologists who have embraced evolutionary perspectives are nativists, who argue than infants possess innate cognitive mechanisms (or modules) which allow them to acquire crucial information, such as language (for a prominent example, see universal grammar).

Evolutionary developmental psychology

Evolutionary developmental psychology can be viewed as a more focused theoretical framework derived from the larger field of evolutionary psychology (EP). Mainstream evolutionary psychology grew out of earlier movements which applied the principles of evolutionary biology to understand the mind and behavior such as sociobiology, ethology, and behavioral ecology, differing from these earlier approaches by focusing on identifying psychological adaptations rather than adaptive behavior. While EDP theory generally aligns with that of mainstream EP, it is distinguished by a conscious effort to reconcile theories of both evolution and development. EDP theory diverges from mainstream evolutionary psychology in both the degree of importance placed on the environment in influencing behavior, and in how evolution has shaped the development of human psychology.

Advocates of EDP assert that evolutionary psychologists, while acknowledging the role of the environment in shaping behavior and making claims as to its effects, rarely develop explicit models (i.e., predictions of how the environment might shape behavior) to support their claims. EDP seeks to distinguish itself from mainstream evolutionary psychology in this way by embracing a developmental systems approach, and emphasizing that function at one level of organization (e.g., the genetic level) effects organization at adjacent levels of an organization. Developmental systems theorists such as Robert Lickliter point out that the products of development are both genetic and epigenetic, and have questioned the strictly gene-centric view of evolution. However, some authors have rebutted the claim that mainstream evolutionary psychologists do not integrate developmental theory into their theoretical programs, and have further questioned the value of developmental systems theory. 

Additionally, evolutionary developmental psychologists emphasize research on psychological development and behaviors across the lifespan. Pioneers of EDP contrast their work with that of mainstream evolutionary psychologists, who they argue focus primarily on adults, especially on behaviors related to socializing and mating.

Evolutionary developmental psychologists have worked to integrate evolutionary and developmental theories, attempting to synthesize the two without discarding the theoretical foundations of either. This effort is evident in the types of questions which researchers working in the EDP paradigm ask; in reference to Nikolaas Tinbergen's four categories of questions, EP typically focuses on evolutionary ("Why") questions, while EDP explicitly integrates proximate questions ("How"), with the assumption that a greater understanding of the former category will yield insights into the latter. See the following table for an overview of Tinbergen's questions.

		Sequential vs. Static Perspective
		Historical/Developmental Explanation of current form in terms of a historical sequence	Current Form Explanation of the current form of species
How vs. Why Questions	Proximate How an individual organism's structures function	Ontogeny Developmental explanations for changes in individuals, from DNA to their current form	Mechanism Mechanistic explanations for how an organism's structures work
	Evolutionary Why a species evolved the structures (adaptations) it has	Phylogeny The history of the evolution of sequential changes in a species over many generations	Adaptation A species trait that evolved to solve a reproductive or survival problem in the ancestral environment

Basic assumptions

The following list summarizes the broad theoretical assumptions of EDP. From "Evolutionary Developmental Psychology," in The Handbook of Evolutionary Psychology:

1. All evolutionarily-influenced characteristics in the phenotype of adults develop, and this requires examining not only the functioning of these characteristics in adults but also their ontogeny.
2. All evolved characteristics develop via continuous and bidirectional gene-environment interactions that emerge dynamically over time.
3. Infants and children are prepared by natural selection to process some information more readily than others.
4. Development is constrained by genetic, environmental, and cultural factors.
5. Infants and children show a high degree of developmental plasticity and adaptive sensitivity to context.
6. An extended childhood is needed in which to learn the complexities of human social communities.
7. Many aspects of childhood serve as preparations for adulthood and were selected over the course of evolution (deferred adaptations).
8. Some characteristics of infants and children were selected to serve an adaptive function at specific times in development and not as preparations for adulthood (ontogenetic adaptations).

Developmental adaptations

EDP assumes that natural selection creates adaptations for specific stages of development, rather than only specifying adult states. Frequently, EDP researchers seek to identify such adaptations, which have been subdivided into deferred adaptations, ontogenetic adaptations, and conditional adaptations.

Deferred adaptations

Some behaviors or traits exhibited during childhood or adolescence may have been selected to serve as preparations for adult life, a type of adaptation that evolutionary developmental psychologists have named "deferred adaptations". Sex differences in children's play may be an example of this type of adaptation: higher frequencies of "rough-and-tumble" play among boys, as well as content differences in fantasy play (cross-culturally, girls engage in more "parenting" play than boys), seem to serve as early preparation for the roles that men and women play in many extant contemporary societies, and, presumably, played over human evolutionary history.

Ontogenetic adaptations

In contrast to deferred adaptations, which function to prepare individuals for future environments (i.e., adulthood), ontogenetic adaptations adapt individuals to their current environment. These adaptations serve a specific function during a particular period of development, after which they are discarded. Ontogenetic adaptations can be physiological (for example, when fetal mammals deriving nutrition and oxygen from the placenta before birth, but no longer utilize the placenta after birth) and psychological. David F. Bjorklund has argued that the imitation of facial gestures by infants, which has a predictable developmental window and seemingly different functions at different ages, shows evidence of being an ontogenetic adaptation.

Conditional adaptations

EDP emphasizes that children display considerable developmental plasticity, and proposes a special type of adaptation to facilitate adaptive developmental plasticity, called a conditional adaptation. Conditional adaptations detect and respond to relevant environmental cues, altering developmental pathways in ways which better adapt an individual to their particular environment. These adaptations allow organisms to implement alternative and contingent life history strategies, depending on environmental factors.

Related research

Social learning and the evolution of childhood

The social brain (or Machiavellian) hypothesis posits that the emergence of a complex social environment (e.g., larger group sizes) served as a key selection pressure in the evolution of human intelligence. Among primates, larger brains result in an extension of the juvenile period, and some authors argue that humans evolved (and/or expanded) novel developmental stages, childhood and adolescence, in response to increasing social complexity and sophisticated social learning.

While many species exhibit social learning to some degree and seemingly possess behavioral traditions (i.e., culture), humans can transmit cultural information across many generations with very high fidelity. High fidelity cultural learning is what many have argued is necessary for cumulative cultural evolution, and has only been definitively observed in humans, although arguments have been made for chimpanzees, orangutans, and New Caledonian crows. Developmentally-oriented researchers have proposed that over-imitation of behavioral models facilitates cultural learning, a phenomenon which emerges in children by age three and is seemingly absent in chimpanzees.

Cooperation and prosociality

Behaviors that benefit other members of one's social group, particularly those which appear costly to the prosocial or "altruistic" individual, have received considerable attention from disciplines interested in the evolution of behavior. Michael Tomasello has argued that cooperation and prosociality are evolved characteristics of human behavior, citing the emergence of "helping" behavior early in development (observed among 18-24 month old infants) as one piece of evidence. Researchers investigating the ontogeny and evolution of human cooperation design experiments intended to reveal the prosociality of infants and young children, then compare children's performance with that of other animals, typically chimpanzees. While some of the helping behaviors exhibited by infants and young children has also been observed in chimpanzees, preschool-age children tend to display greater prosociality than both human-raised and semi-free-ranging adult chimps.

Life history strategies and developmental plasticity

EDP researchers emphasize that evolved strategies are context dependent, in the sense that a strategy which is optimal in one environment will often be sub-optimal in another environment. They argue that this will result in natural selection favoring "adaptive developmental plasticity," allowing an organism to alter its developmental trajectory in response to environmental cues.

Related to this is the idea of a life history strategy, which can be conceptualized as a chain of resource-allocation decisions (e.g., allocating resources towards growth or towards reproduction) that an organism makes. Biologists have used life history theory to characterize between-species variation in resource-allocation in terms of a fast-slow continuum (see r/K selection theory), and, more recently, some anthropologists and psychologists have applied this continuum to understand within-species variation in trade-offs between reproductive and somatic effort.

Some authors argue that childhood environment and early life experiences are highly influential in determining an individual's life history strategy. Factors such as exposure to violence, harsh child-rearing, and environmental unpredictability (e.g., frequent moving, unstable family composition) have been shown to correlate with the proposed behavioral indicators of "fast" life history strategies (e.g., early sexual maturation, unstable couple relationships, impulsivity, and reduced cooperation), where current reproduction is prioritized over future reproduction.

Criticism

John Tooby, Leda Cosmides, and H. Clark Barrett have refuted claims that mainstream evolutionary psychology neglects development, arguing that their discipline is, in reality, exceptionally interested in and highly considerate of development. In particular, they cite cross-cultural studies as a sort of natural developmental "experiment," which can reveal the influence of culture in shaping developmental outcomes. The authors assert that the arguments of developmental systems theorists consists largely of truisms, of which evolutionary psychologists are well aware, and that developmental systems theory has no scientific value because it fails to generate any predictions.

Debra Lieberman similarly objected to the characterization of evolutionary psychology as ignorant of developmental principles. Lieberman argued that both developmental systems theorists and evolutionary psychologists share a common goal of uncovering species-typical cognitive architecture, as well as the ontogeny of that architecture.

Global health

From Wikipedia, the free encyclopedia

Headquarters of the World Health Organization in Geneva, Switzerland.

Global health is the health of populations in the global context; it has been defined as "the area of study, research and practice that places a priority on improving health and achieving equity in health for all people worldwide". Problems that transcend national borders or have a global political and economic impact are often emphasized. Thus, global health is about worldwide health improvement (including mental health), reduction of disparities, and protection against global threats that disregard national borders. Global health is not to be confused with international health, which is defined as the branch of public health focusing on developing nations and foreign aid efforts by industrialized countries. Global health can be measured as a function of various global diseases and their prevalence in the world and threat to decrease life in the present day.

The predominant agency associated with global health (and international health) is the World Health Organization (WHO). Other important agencies impacting global health include UNICEF and World Food Programme. The United Nations system has also played a part with cross-sectoral actions to address global health and its underlying socioeconomic determinants with the declaration of the Millennium Development Goals and the more recent Sustainable Development Goals.

Definition

Global health employs several perspectives that focus on the determinants and distribution of health in international contexts:

• Medicine describes the pathology of diseases and promotes prevention, diagnosis, and treatment.
• Public health emphasizes the health of populations.
• Epidemiology helps identify risk factors and causes of health problems.
• Demography provides data for policy decisions.
• Economics emphasizes the cost-effectiveness and cost-benefit approaches for the optimal allocation of health resources.
• Other social sciences such as sociology, development studies, psychology, anthropology, cultural studies, and law can help understand the determinants of health in societies.

Both individuals and organizations working in the domain of global health often face many questions regarding ethical and human rights. Critical examination of the various causes and justifications of health inequities is necessary for the success of proposed solutions. Such issues are discussed at the bi-annual Global Summits of National Ethics/Bioethics Councils, next in March 2016 in Berlin, with experts from WHO and UNESCO, by invitation of the German Ethics Council.

History

The 19th century held major discoveries in medicine and public health. The Broad Street cholera outbreak of 1854 was central to the development of modern epidemiology. The microorganisms responsible for malaria and tuberculosis were identified in 1880 and 1882, respectively. The 20th century saw the development of preventive and curative treatments for many diseases, including the BCG vaccine (for tuberculosis) and penicillin in the 1920s. The eradication of smallpox, with the last naturally occurring case recorded in 1977, raised hope that other diseases could be eradicated as well.

Important steps were taken towards global cooperation in health with the formation of the United Nations (UN) and the World Bank Group in 1945, after World War II. In 1948, the member states of the newly formed United Nations gathered to create the World Health Organization. A cholera epidemic that took 20,000 lives in Egypt in 1947 and 1948 helped spur the international community to action. The WHO published its Model List of Essential Medicines, and the 1978 Alma Ata declaration underlined the importance of primary health care.

At a United Nations Summit in 2000, member nations declared eight Millennium Development Goals (MDGs), which reflected the major challenges facing human development globally, to be achieved by 2015. The declaration was matched by unprecedented global investment by donor and recipient countries. According to the UN, these MDGs provided an important framework for development and significant progress has been made in a number of areas. However, progress has been uneven and some of the MDGs were not fully realized including maternal, newborn and child health and reproductive health. Building on the MDGs, a new Sustainable Development Agenda with 17 Sustainable Development Goals (SDGs) has been established for the years 2016-2030. The first goal being an ambitious and historic pledge to end poverty. On 25 September 2015, the 193 countries of the UN General Assembly adopted the 2030 Development Agenda titled Transforming our world: the 2030 Agenda for Sustainable Development.

In 2015 a book titled "To Save Humanity" was published, with nearly 100 essays regarding today's most pressing global health issues. The essays were authored by global figures in politics, science, and advocacy ranging from Bill Clinton to Peter Piot, and addressed a wide range of issues including vaccinations, antimicrobial resistance, health coverage, tobacco use, research methodology, climate change, equity, access to medicine, and media coverage of health research.

Measures

Measures of global health include disability-adjusted life year (DALY), quality-adjusted life years (QALYs), and mortality rate.

Disability-adjusted life years

Disability-adjusted life years per 100,000 people in 2004.

  No data

  Less than 9,250

  9,250–16,000

  16,000–22,750

  22,750–29,500

  29,500–36,250

  36,250–43,000

  43,000–49,750

  49,750–56,500

  56,500–63,250

  63,250–70,000

  70,000–80,000

  Over 80000

The DALY is a summary measure that combines the impact of illness, disability, and mortality by measuring the time lived with disability and the time lost due to premature mortality. One DALY can be thought of as one lost year of "healthy" life. The DALY for a disease is the sum of the years of life lost due to premature mortality and the years lost due to disability for incident cases of the health condition.

Quality-adjusted life years

QALYs combine expected survival with expected quality of life into a single number: if an additional year of healthy life is worth a value of one (year), then a year of less healthy life is worth less than one (year). QALY calculations are based on measurements of the value that individuals place on expected years of survival. Measurements can be made in several ways: by techniques that simulate gambles about preferences for alternative states of health, with surveys or analyses that infer willingness to pay for alternative states of health, or through instruments that are based on trading off some or all likely survival time that a medical intervention might provide in order to gain less survival time of higher quality.

Infant and child mortality

Infant mortality and child mortality for children under age 5 are more specific than DALYs or QALYs in representing the health in the poorest sections of a population, and are thus especially useful when focusing on health equity.

Morbidity

Morbidity measures include incidence rate, prevalence, and cumulative incidence, with incidence rate referring to the risk of developing a new health condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during a time period, morbidity is better expressed as a proportion or a rate.

Health conditions

The diseases and health conditions targeted by global health initiatives are sometimes grouped under "diseases of poverty" versus "diseases of affluence", although the impact of globalization is increasingly blurring the lines between the two.

Respiratory infections

Infections of the respiratory tract and middle ear are major causes of morbidity and mortality worldwide. Some respiratory infections of global significance include tuberculosis, measles, influenza, and pneumonias caused by pneumococci and Haemophilus influenzae. The spread of respiratory infections is exacerbated by crowded conditions, and poverty is associated with more than a 20-fold increase in the relative burden of lung infections.

Diarrheal diseases

Diarrhea is the second most common cause of child mortality worldwide, responsible for 17% of deaths of children under age 5. Poor sanitation can increase transmission of bacteria and viruses through water, food, utensils, hands, and flies. Dehydration due to diarrhea can be effectively treated through oral rehydration therapy with dramatic reductions in mortality. Important nutritional measures include the promotion of breastfeeding and zinc supplementation. While hygienic measures alone may be insufficient for the prevention of rotavirus diarrhea, it can be prevented by a safe and potentially cost-effective vaccine.

Maternal health

Maternal health clinic in Afghanistan (source: Merlin)

Complications of pregnancy and childbirth are the leading causes of death among women of reproductive age in many developing countries: a woman dies from complications from childbirth approximately every minute. According to the World Health Organization's 2005 World Health Report, poor maternal conditions are the fourth leading cause of death for women worldwide, after HIV/AIDS, malaria, and tuberculosis. Most maternal deaths and injuries can be prevented, and such deaths have been largely eradicated in the developed world. Targets for improving maternal health include increasing the number of deliveries accompanied by skilled birth attendants.

68 low-income countries tracked by the WHO- and UNICEF-led collaboration Countdown to 2015 are estimated to hold for 97% of worldwide maternal and child deaths.

HIV/AIDS

The HIV/AIDS epidemic has highlighted the global nature of human health and welfare and globalisation has given rise to a trend toward finding common solutions to global health challenges. Numerous international funds have been set up in recent times to address global health challenges such as HIV. Since the beginning of the epidemic, more than 70 million people have been infected with the HIV virus and about 35 million people have died of HIV. Globally, 36.9 million [31.1–43.9 million] people were living with HIV at the end of 2017. An estimated 0.8% [0.6-0.9%] of adults aged 15–49 years worldwide are living with HIV, although the burden of the epidemic continues to vary considerably between countries and regions. The WHO African region remains most severely affected, with nearly 1 in every 25 adults (4.1%) living with HIV and accounting for nearly two-thirds of the people living with HIV worldwide. Human immunodeficiency virus (HIV) is transmitted through unprotected sex, unclean needles, blood transfusions, and from mother to child during birth or lactation. Globally, HIV is primarily spread through sexual intercourse. The risk-per-exposure with vaginal sex in low-income countries from female to male is 0.38% and male to female is 0.3%. The infection damages the immune system, leading to acquired immunodeficiency syndrome (AIDS) and eventually, death. Antiretroviral drugs prolong life and delay the onset of AIDS by minimizing the amount of HIV in the body.

Malaria

Malaria is a mosquito-borne infectious disease caused by the parasites of the genus Plasmodium. Symptoms may include fever, headaches, chills, and nausea. Each year, there are approximately 500 million cases of malaria worldwide, most commonly among children and pregnant women in developing countries. The WHO African Region carries a disproportionately high share of the global malaria burden. In 2016, the region was home to 90% of malaria cases and 91% of malaria deaths. The use of insecticide-treated bednets is a cost-effective way to reduce deaths from malaria, as is prompt artemisinin-based combination therapy, supported by intermittent preventive therapy in pregnancy. International travellers to endemic zones are advised chemoprophylaxis with antimalarial drugs like Atovaquone-proguanil, doxycycline, or mefloquine.

Nutrition

In 2010, about 104 million children were underweight, and undernutrition contributes to about one third of child deaths around the world. (Undernutrition is not to be confused with malnutrition, which refers to poor proportion of food intake and can thus refer to obesity.) Undernutrition impairs the immune system, increasing the frequency, severity, and duration of infections (including measles, pneumonia, and diarrhea). Infection can further contribute to malnutrition. Deficiencies of micronutrient, such as vitamin A, iron, iodine, and zinc, are common worldwide and can compromise intellectual potential, growth, development, and adult productivity. Interventions to prevent malnutrition include micronutrient supplementation, fortification of basic grocery foods, dietary diversification, hygienic measures to reduce spread of infections, and the promotion of breastfeeding.

Violence against women

Violence against women has been defined as: "physical, sexual and psychological violence occurring in the family and in the general community, including battering, sexual abuse of children, dowry-related violence, rape, female genital mutilation and other traditional practices harmful to women, non-spousal violence and violence related to exploitation, sexual harassment and intimidation at work, in educational institutions and elsewhere, trafficking in women, forced prostitution and violence perpetrated or condoned by the state." In addition to causing injury, violence may increase "women’s long-term risk of a number of other health problems, including chronic pain, physical disability, drug and alcohol abuse, and depression".

Although statistics can be difficult to obtain as many cases go unreported, it is estimated that one in every five women faces some form of violence during her lifetime, in some cases leading to serious injury or even death. Risk factors for being a perpetrator include low education, past exposure to child maltreatment or witnessing violence between parents, harmful use of alcohol, attitudes accepting of violence and gender inequality. Equality of women has been addressed in the Millennium development goals.

Chronic disease

Approximately 80% of deaths linked to non-communicable diseases occur in developing countries.For instance, urbanization and aging have led to increasing poor health conditions related to non-communicable diseases in India. The fastest-growing causes of disease burden over the last 26 years were diabetes (rate increased by 80%) and ischemic heart disease (up 34%). More than 60% of deaths, about 6.1 million, in 2016 were due to NCDs, up from about 38% in 1990. Increases in refugee urbanization, has led to a growing number of people diagnosed with chronic noncommunicable diseases.

In September 2011, the United Nations is hosting its first General Assembly Special Summit on the issue of non-communicable diseases. Noting that non-communicable diseases are the cause of some 35 million deaths each year, the international community is being increasingly called to take measures for the prevention and control of chronic diseases and mitigate their impacts on the world population, especially on women, who are usually the primary caregivers.

For example, the rate of type 2 diabetes, associated with obesity, has been on the rise in countries previously plagued by hunger. In low-income countries, the number of individuals with diabetes is expected to increase from 84 million to 228 million by 2030. Obesity, a preventable condition, is associated with numerous chronic diseases, including cardiovascular conditions, stroke, certain cancers, and respiratory disease. About 16% of the global burden of disease, measured as DALYs, has been accounted for by obesity.

Neglected tropical diseases

More than one billion people were treated for at least one neglected tropical disease in 2015. Neglected tropical diseases are a diverse group of infectious diseases that are endemic in tropical and subtropical regions of 149 countries, primarily effecting low and middle income populations in Africa, Asia, and Latin America. They are variously caused by bacteria (Trachoma, Leprosy), viruses (Dengue, Rabies), protozoa (Human African trypanosomiasis, Chagas), and helminths (Schistosomiasis, Onchocerciasis, Soil transmitted helminths). The Global Burden of Disease Study concluded that neglected tropical diseases comprehensively contributed to approximately 26.06 million disability-adjusted life years in 2010, as well as significant deleterious economic effects. In 2011, the World Health Organization launched a 2020 Roadmap for neglected tropical diseases, aiming for the control or elimination of 10 common diseases. The 2012 London Declaration builds on this initiative, and called on endemic countries and the international community to improve access to clean water and basic sanitation, improved living conditions, vector control, and health education, to reach the 2020 goals. In 2017, a WHO report cited 'unprecedented progress' against neglected tropical diseases since 2007, especially due to mass drug administration of drugs donated by pharmaceutical companies.

Health interventions

Global interventions for improved child health and survival include the promotion of breastfeeding, zinc supplementation, vitamin A fortification, salt iodization, hygiene interventions such as hand-washing, vaccinations, and treatments of severe acute malnutrition. The Global Health Council suggests a list of 32 treatments and health interventions that could potentially save several million lives each year.

Many populations face an "outcome gap", which refers to the gap between members of a population who have access to medical treatment versus those who do not. Countries facing outcome gaps lack sustainable infrastructure. In Guatemala, a subset of the public sector, the Programa de Accessibilidad a los Medicamentos ("Program for Access to Medicines"), had the lowest average availability (25%) compared to the private sector (35%). In the private sector, highest- and lowest-priced medicines were 22.7 and 10.7 times more expensive than international reference prices respectively. Treatments were generally unaffordable, costing as much as 15 days wages for a course of the antibiotic ceftriaxone. The public sector in Pakistan, while having access to medicines at a lower price than international reference prices, has a chronic shortage of and lack of access to basic medicines.

Journalist Laurie Garrett argues that the field of global health is not plagued by a lack of funds, but that more funds do not always translate into positive outcomes. The problem lies in the way these funds are allocated, as they are often disproportionately allocated to alleviating a single disease.

In its 2006 World Health Report, the WHO estimated a shortage of almost 4.3 million doctors, midwives, nurses, and support workers worldwide, especially in sub-Saharan Africa.

Global Health Security Agenda

The Global Health Security Agenda (GHSA) is "a multilateral, multi-sector effort that includes 60 participating countries and numerous private and public international organizations focused on building up worldwide health security capabilities toward meeting such threats" as the spread of infectious disease. On March 26-28, 2018, the GHSA held its last high-level meeting which was located in Tbilisi, Georgia on biosurveillance of infectious disease threats, "which include such modern-day examples as HIV/AIDS, severe acute respiratory syndrome (SARS), H1N1 influenza, multi-drug resistant tuberculosis — any emerging or reemerging disease that threatens human health and global economic stability." This event brought together GHSA partner countries, contributing countries of Real-Time Surveillance Action Package, and international partner organizations supporting the strengthening of capacities to detect infectious disease threats within the Real-Time Surveillance Action Package and other cross-cutting packages. Georgia is the lead country for the Real-Time Surveillance Action Package.

Technology Feels Like It’s Accelerating — Because It Actually Is

By Alison E. Berman and Jason Dorrier

Mar 22, 2016

Original link:  https://singularityhub.com/2016/03/22/technology-feels-like-its-accelerating-because-it-actually-is/

 

This is the second in a four-part series looking at the big ideas in Ray Kurzweil’s book The Singularity Is Near. ​Be sure to read the other articles:

• Will the End of Moore’s Law Halt Computing’s Exponential Rise?
• How to Think Exponentially and Better Predict the Future
• Ray Kurzweil Predicts Three Technologies Will Define Our Future

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Technology goes beyond mere tool making; it is a process of creating ever more powerful technology using the tools from the previous round of innovation. –Ray Kurzweil

A decade ago, smartphones (as we know them by today’s standards) didn’t exist. Three decades earlier, no one even owned a computer. Think about that—the first personal computers arrived about 40 years ago. Today, it seems nearly everyone is gazing at a glowing, handheld computer. (In fact, two-thirds of Americans own one, according to a Pew Report.)

Intuitively, it feels like technology is progressing faster than ever. But is it really? According to Ray Kurzweil—yes, it absolutely is. In his book The Singularity Is Near, Kurzweil shows technology’s quickening pace and explains the force behind it all.

This article will explore Kurzweil’s explanation of this driving force, which he dubbed the law of accelerating returns, and the surprising implications of technology’s acceleration.

Moore’s Law is famous—but it isn’t special

Computer chips have become increasingly powerful while costing less. That’s because over the last five decades the number of transistors—or the tiny electrical components that perform basic operations—on a single chip have been doubling regularly.

This exponential doubling, known as Moore’s Law, is the reason a modern smartphone affordably packs so much dizzying capability into such a small package.

[Moore’s Law may be nearing certain physical limitations that will be challenging to overcome. Go here to learn how broad exponential growth in computing can continue.]

The technological progress in computer chips is well known—but surprisingly, it isn’t a special case. A range of other technologies demonstrate similar exponential growth, whether bits of data stored or DNA base pairs recorded. The outcome is the same: capabilities have increased by thousands, millions, and billions for less cost in just decades.


The above charts show a few examples of accelerating technologies, but more examples are plentiful. These do not directly depend on the doubling of transistor counts—and yet each one moves along its own exponential curve just as computer chips do.

So, what’s going on?

According to the law of accelerating returns, the pace of technological progress—especially information technology—speeds up exponentially over time because there is a common force driving it forward. Being exponential, as it turns out, is all about evolution.

Technology is an evolutionary process

Let’s begin with biology, a familiar evolutionary process.

Biology hones natural “technologies,” so to speak. Recorded within the DNA of living things are blueprints of useful tools known as genes. Due to selective pressure—or “survival of the fittest”—advantageous innovations are passed along to offspring.

As this process plays out generation after generation over geological timescales, chaotically yet incrementally, incredible growth takes place. By building on genetic progress rather than starting over, organisms have increased in complexity and capability over time. This innovative power is evident nearly everywhere we look on Earth today.  As Kurzweil writes:

Evolution applies positive feedback.  The more capable methods resulting from one stage of evolutionary progress are used to create the next stage.”

Biology’s many innovations include cells, bones, eyes, thumbs, brains—and from thumbs and brains, technology. According to Kurzweil, technology is also an evolutionary process, like biology, only it moves from one invention to the next much faster.


Civilizations advance by “repurposing” the ideas and breakthroughs of their predecessors. Similarly, each generation of technology builds on the advances of previous generations, and this creates a positive feedback loop of improvements.

Kurzweil’s big idea is that each new generation of technology stands on the shoulders of its predecessors—in this way, improvements in technology enable the next generation of even better technology.

Technological evolution speeds up exponentially

Because each generation of technology improves over the last, the rate of progress from version to version speeds up.

To see this, imagine making a chair with hand tools, power tools, and finally assembly lines. Production gets faster after each step. Now imagine each generation of these tools is also used to design and build better tools. Kurzweil suggests such a process is at play in the design of ever-faster computer chips with the software and computers used by engineers.

The first computers were designed on paper and assembled by hand. Today, they are designed on computer workstations with the computers themselves working out many details of the next generation’s design, and are then produced in fully automated factories with only limited human intervention. – Ray Kurzweil, The Singularity Is Near

This acceleration can be measured in the “returns” of the technology—such as speed, efficiency, price-performance, and overall “power”—which improve exponentially too.

The acceleration of acceleration: It’s a bit like climbing a mountain and receiving a jetpack.

Further, as a technology becomes more effective, it attracts more attention. The result is a flood of new resources—such as increased R&D budgets, recruiting top talent, etc.—which are directed to further improving the technology.

This wave of new resources triggers a “second level” of exponential growth, where the rate of exponential growth (the exponent) also begins accelerating.

However, specific paradigms (e.g., integrated circuits) won’t grow exponentially forever. They grow until they’ve exhausted their potential, at which point a new paradigm replaces the old one.

The surprising implications of the law of accelerating returns

Kurzweil wrote in 2001 that every decade our overall rate of progress was doubling, “We won’t experience 100 years of progress in the 21st century—it will be more like 20,000 years of progress (at today’s rate).” 

This suggests that the horizons for amazingly powerful technologies may be closer than we realize. Some of Ray Kurzweil’s predictions from the last 25 years may have seemed a stretch at the time—but many were right.

Like in 1990 when he predicted that a computer would beat a pro chess player by 1998, which came true in 1997 when Garry Kasparov lost to IBM’s Deep Blue. (Now, in 2016, a computer has mastered the even more complex game Go—an accomplishment not expected by some experts for another decade.)

We’re only 15 years into the 21^st century and the progress has been pretty stunning—the global adoption of the Internet, smartphones, ever-more agile robots, AI that learns. We sequenced the first human genome in 2004 at a cost of hundreds of millions of dollars. Now, machines can sequence 18,000 annually for $1,000 a genome.

These are just a few examples of the law of accelerating returns driving progress forward. Because the future is approaching much faster than we realize, it’s critical to think exponentially about where we’re headed and how we’ll get there.

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To learn more about the exponential pace of technology and Ray Kurzweil’s predictions, read his 2001 essay “The Law of Accelerating Returns” and his book, The Singularity Is Near.

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