Molecular
diagnostics uses techniques such as mass spectrometry and gene chips to
capture the expression patterns of genes and proteins
The field of molecular biology grew in the late twentieth century, as did its clinical application. In 1980, Yuet Wai Kanet al. suggested a prenatal genetic test for Thalassemia that did not rely upon DNA sequencing—then in its infancy—but on restriction enzymes that cut DNA where they recognised specific short sequences, creating different lengths of DNA strand depending on which allele (genetic variation) the fetus possessed. In the 1980s, the phrase was used in the names of companies such as Molecular Diagnostics Incorporated and Bethseda Research Laboratories Molecular Diagnostics.
During the 1990s, the identification of newly discovered
genes and new techniques for DNA sequencing led to the appearance of a
distinct field of molecular and genomic laboratory medicine; in 1995,
the Association for Molecular Pathology (AMP) was formed to give it structure. In 1999, the AMP co-founded The Journal of Medical Diagnostics. Informa Healthcare launched Expert Reviews in Medical Diagnostics in 2001. From 2002 onwards, the HapMap Project aggregated information on the one-letter genetic differences that recur in the human population—the single nucleotide polymorphisms—and their relationship with disease. In 2012, molecular diagnostic techniques for Thalassemia use genetic hybridization tests to identify the specific single nucleotide polymorphism causing an individual's disease.
The industrialisation of molecular biology assay tools has made it practical to use them in clinics. Miniaturisation into a single handheld device can bring medical diagnostics into the clinic and into the office or home. The clinical laboratory requires high standards of reliability; diagnostics may require accreditation or fall under medical device regulations. As of 2011, some US clinical laboratories nevertheless used assays sold for "research use only".
Automation and sample barcoding maximise throughput and
reduce the possibility of error or contamination during manual handling
and results reporting. Single devices to do the assay from beginning to
end are now available.
Molecular diagnostics uses in vitrobiological assays such as PCR-ELISA or Fluorescence in situ hybridization. The assay detects a molecule, often in low concentrations, that is a marker
of disease or risk in a sample taken from a patient. Preservation of
the sample before analysis is critical. Manual handling should be
minimised. The fragile RNA
molecule poses certain challenges. As part of the cellular process of
expressing genes as proteins, it offers a measure of gene expression but
it is vulnerable to hydrolysis and breakdown by ever-present RNAse enzymes. Samples can be snap-frozen in liquid nitrogen or incubated in preservation agents.
Because molecular diagnostics methods can detect sensitive markers, these tests are less intrusive than a traditional biopsy. For example, because cell-free nucleic acids exist in human plasma, a simple blood sample can be enough to sample genetic information from tumours, transplants or an unborn fetus. Many, but not all, molecular diagnostics methods based on nucleic acids detection use polymerase chain reaction (PCR) to vastly increase the number of nucleic acid molecules, thereby amplifying the target sequence(s) in the patient sample.
PCR is a method that a template DNA is amplified using synthetic
primers, a DNA polymerase, and dNTPs. The mixture is cycled between at
least 2 temperatures: a high temperature for denaturing double-stranded
DNA into single-stranded molecules and a low temperature for the primer
to hybridize to the template and for the polymerase to extend the
primer. Each temperature cycle theoretically doubles the quantity of
target sequence. Detection of sequence variations using PCR typically
involves the design and use oligonucleotide reagents that amplify the
variant of interest more efficiently than wildtype sequence. PCR is
currently the most widely used method for detection of DNA sequences. The detection of the marker might use real time PCR, direct sequencing,microarray chips—prefabricated chips that test many markers at once, or MALDI-TOF The same principle applies to the proteome and the genome. High-throughput protein arrays can use complementary DNA or antibodies to bind and hence can detect many different proteins in parallel. Molecular diagnostic tests vary widely in sensitivity, turn around
time, cost, coverage and regulatory approval. They also vary in the
level of validation applied in the laboratories using them. Hence,
robust local validation in accordance with the regulatory requirements
and use of appropriate controls is required especially where the result
may be used to inform a patient treatment decision.
Benefits
A
microarray chip contains complementary DNA (cDNA) to many sequences of
interest. The cDNA fluoresces when it hybridises with a matching DNA
fragment in the sample.
Conventional prenatal tests for chromosomal abnormalities such as Down syndrome rely on analysing the number and appearance of the chromosomes—the karyotype. Molecular diagnostics tests such as microarray comparative genomic hybridisation
test a sample of DNA instead, and because of cell-free DNA in plasma,
could be less invasive, but as of 2013 it is still an adjunct to the
conventional tests.
Some of a patient's single nucleotide polymorphisms—slight differences in their DNA—can help predict how quickly they will metabolise particular drugs; this is called pharmacogenomics. For example, the enzyme CYP2C19 metabolises several drugs, such as the anti-clotting agent Clopidogrel, into their active forms. Some patients possess polymorphisms in specific places on the 2C19 gene that make poor metabolisers
of those drugs; physicians can test for these polymorphisms and find
out whether the drugs will be fully effective for that patient. Advances in molecular biology have helped show that some syndromes that
were previously classed as a single disease are actually multiple
subtypes with entirely different causes and treatments. Molecular
diagnostics can help diagnose the subtype—for example of infections and cancers—or the genetic analysis of a disease with an inherited component, such as Silver-Russell syndrome.
Molecular diagnostics are used to identify infectious diseases such as chlamydia, influenza virus and tuberculosis; or specific strains such as H1N1 virus or SARS-CoV-2. Genetic identification can be swift; for example a loop-mediated isothermal amplification test diagnoses the malaria parasite and is rugged enough for developing countries. But despite these advances in genome analysis, in 2013 infections are still more often identified by other means—their proteome, bacteriophage, or chromatographic profile. Molecular diagnostics are also used to understand the specific strain of the pathogen—for example by detecting which drug resistance genes it possesses—and hence which therapies to avoid. In addition, assays based on metagenomic next generation sequencing can
be implemented to identify pathogenic organisms without bias.
A patient's genome may include an inherited or random
mutation which affects the probability of developing a disease in the
future. For example, Lynch syndrome is a genetic disease that predisposes patients to colorectal and other cancers; early detection can lead to close monitoring that improves the patient's chances of a good outcome. Cardiovascular risk is indicated by biological markers and screening can measure the risk that a child will be born with a genetic disease such as Cystic fibrosis. Genetic testing is ethically complex: patients may not want the stress of knowing their risk. In countries without universal healthcare, a known risk may raise insurance premiums.
Cancer is a change in the cellular processes that cause a tumour to grow out of control. Cancerous cells sometimes have mutations in oncogenes, such as KRAS and CTNNB1 (β-catenin). Analysing the molecular signature of cancerous cells—the DNA and its levels of expression via messenger RNA—enables physicians to characterise the cancer and to choose the best therapy for their patients. As of 2010, assays that incorporate an array of antibodies against
specific protein marker molecules are an emerging technology; there are
hopes for these multiplex assays that could measure many markers at
once. Other potential future biomarkers include micro RNA molecules, which cancerous cells express more of than healthy ones.
Cancer is a disease with excessive molecular causes and
constant evolution. There's also heterogeneity of disease even in an
individual. Molecular studies of cancer have proved the significance of
driver mutations in the growth and metastasis of tumors. Many technologies for detection of sequence variations have been
developed for cancer research. These technologies generally can be
grouped into three approaches: polymerase chain reaction (PCR), hybridization, and next-generation sequencing (NGS). Currently, a lot of PCR and hybridization assays have been approved by FDA as in vitro diagnostics. NGS assays, however, are still at an early stage in clinical diagnostics.
To do the molecular diagnostic test for cancer, one of the
significant issue is the DNA sequence variation detection. Tumor biopsy
samples used for diagnostics always contain as little as 5% of the
target variant as compared to wildtype sequence. Also, for noninvasive
applications from peripheral blood or urine, the DNA test must be
specific enough to detect mutations at variant allele frequencies of
less than 0.1%.
Currently, by optimizing the traditional PCR, there's a
new invention, amplification-refractory mutation system (ARMS) is a
method for detecting DNA sequence variants in cancer. The principle
behind ARMS is that the enzymatic extension activity of DNA polymerases
is highly sensitive to mismatches near the 3' end of primer. Many different companies have developed diagnostics tests based on ARMS PCR primers. For instance, Qiagen therascreen, Roche cobas and Biomerieux THxID have developed FDA approved PCR tests for detecting lung, colon cancer
and metastatic melanoma mutations in the KRAS, EGFR and BRAF genes.
Their IVD kits were basically validated on genomic DNA extracted from
FFPE tissue.
There are also microarrays that utilize hybridization
mechanism to diagnose cancer. More than a million of different probes
can be synthesized on an array with Affymetrix's Genechip technology
with a detection limit of one to ten copies of mRNA per well. Optimized microarrays are typically considered to produce repeatable relative quantitation of different targets. Currently, FDA have already approved a number of diagnostics assays
utilizing microarrays: Agendia's MammaPrint assays can inform the breast
cancer recurrence risk by profiling the expression of 70 genes related
to breast cancer; Autogenomics INFNITI CYP2C19 assay can profile genetic polymorphisms,
whose impacts on therapeutic response to antidepressants are great; and Affymetrix's CytoScan Dx can evaluate intellectual disabilities and congenital disorders by analyzing chromosomal mutation.
In the future, the diagnostic tools for cancer will likely
to focus on the Next Generation Sequencing (NGS). By utilizing DNA and
RNA sequencing to do cancer diagnostics, technology in the field of
molecular diagnostics tools will develop better. Although NGS throughput
and price have dramatically been reduced over the past 10 years by
roughly 100-fold, we remain at least 6 orders of magnitude away from
performing deep sequencing at a whole genome level. Currently, Ion Torrent developed some NGS panels based on translational
AmpliSeq, for example, the Oncomine Comprehensive Assay. They are focusing on utilizing deep sequencing of cancer-related genes to detect rare sequence variants.
Molecular diagnostics tool can be used for cancer risk
assessment. For example, the BRCA1/2 test by Myriad Genetics assesses
women for lifetime risk of breast cancer. Also, some cancers are not always employed with clear symptoms. It is
useful to analyze people when they do not show obvious symptoms and thus
can detect cancer at early stages. For example, the ColoGuard test may
be used to screen people over 55 years old for colorectal cancer. Cancer is a longtime-scale disease with various progression steps,
molecular diagnostics tools can be used for prognosis of cancer
progression. For example, the OncoType Dx test by Genomic Health can
estimate risk of breast cancer. Their technology can inform patients to
seek chemotherapy when necessary by examining the RNA expression levels
in breast cancer biopsy tissue.
With rising government support in DNA molecular
diagnostics, it is expected that an increasing number of clinical DNA
detection assays for cancers will become available soon. Currently,
research in cancer diagnostics are developing fast with goals for lower
cost, less time consumption and simpler methods for doctors and
patients.
Allergy
Molecular diagnostics is increasingly used in allergology,
especially for food and respiratory allergy. Conventional diagnosis is
based on clinical history, skin-prick testing and measurement of serum allergen-specific IgE
to whole allergen extracts. Molecular-based allergy diagnostics, also
called component-resolved diagnostics, measures IgE to individual
allergen molecules rather than only to extracts. This can help
distinguish genuine sensitization from cross-reactivity, refine
assessment of clinical risk in some allergies, and support decisions
about allergen immunotherapy. Multiplex platforms, such as Allergy
Explorer (ALEX), can test IgE reactivity to many allergen extracts and
molecular components in a single assay. Precision allergy molecular
diagnosis (PAMD®) is a broader diagnostic approach using molecular IgE
profiles to guide prognosis, risk assessment and personalized
management, although results must be interpreted together with the
patient’s clinical history.
Greatness is a concept of a state of exceptional superiority affecting a person or object
in a particular place or area. Greatness can also be attributed to
individuals who possess a natural ability to be better than all others.
An example of an expression of the concept in a qualified sense would be
"Hector is the definition of greatness" or "Napoleon was one of the greatest wartime leaders". In the unqualified sense it might be stated "George Washington
achieved greatness within his own lifetime", thus implying that
"greatness" is a definite and identifiable quality. Application of the
terms "great" and "greatness" is dependent on the perspective and subjective judgements of those who apply them. Whereas in some cases the perceived greatness of a person, place or
object might be agreed upon by many, this is not necessarily the case,
and the perception of greatness may be both fiercely contested and
highly idiosyncratic.
Since the publication of Francis Galton's Hereditary Genius in 1869, and especially with the accelerated development of intelligence tests
in the early 1900s, there has been a vast amount of social scientific
research published relative to the question of greatness. Much of this
research does not actually use the term great in describing itself, preferring terms such as eminence, genius, exceptional achievement, etc. Historically the major intellectual battles over this topic have focused around the questions of nature versus nurture or person versus context. Today the importance of both dimensions is accepted by all, but
disagreements over the relative importance of each are still reflected
in variations in research emphases.
Early scientific research on greatness had a strong genetic
emphasis and focused on intelligence as the driving force behind the
concept.
Hereditary Genius – Galton (1869)
The earliest such research, Hereditary Genius, by Francis Galton
(1869), argued that people vary hugely in "natural ability" which is
allegedly inherited biologically. Those at the very top end of the
range, i.e., geniuses, become according to Galton the "eminent" achievers of their generation. To prove this thesis Galton collected
data showing that genius clusters in what he termed "Notable Family
Lines", such as those of Bernoulli, Cassini, Darwin, Herschel, and Jussieu in science, or Bach in music.
Galton then calculated the odds of eminent people having
eminent relations, taking into account the closeness of the biological
connection (e.g., son vs grandson), and the magnitude of achievement of
the eminent parent. His findings were as anticipated: the more famous
the parent (i.e., the greater level of presumed "natural ability"), the
greater likelihood there would be illustrious relatives; and the closer
the blood tie, the greater those odds.
Early Mental Traits of 300 Geniuses – Cox (1926)
Catharine Cox's book on The Early Mental Traits of Three Hundred Geniuses (1926), was similar to Galton's in its orientation. Using the method that her mentor, Stanford Psychology Professor Lewis Terman,
had developed for differentiating children in terms of intelligence,
Cox coded records of childhood and adolescent achievements of 301
historic eminent leaders and creators to estimate what their IQs
would have been on the basis of intellectual level of such achievements
relative to the age at which they were accomplished. For example, John Stuart Mill
reportedly studied Greek at 3, read Plato at 7, and learned calculus at
11. As such, what he was doing at 5, the average person couldn't do
until 9 years, 6 months of age, giving Mill an estimated IQ of 190.
Cox found that the perceived eminence of those with the
highest IQs was higher than that of those attaining lower IQ estimates,
and that those with higher IQs also exhibited more versatility in their
achievements. For example, da Vinci, Michelangelo, Descartes, Benjamin Franklin, Goethe, and others with IQs in the mid 160s or above were superior in their versatility to those attaining lower scores, such as George Washington, Palestrina, or Philip Sheridan.
The work of both Cox and Galton has been criticized for
failing to take sufficient account of the role of nurture, or more
specifically socio-economic and educational advantage, in the achievements of these historical greats.
Cultural approach
There was one major anthropological study of genius, and it
was triggered specifically by the author's contentions with Galton's
work.
Configurations of Cultural Growth – Kroeber (1944)
Alfred Kroeber's Configurations of Cultural Growth
(1944) looked at many of the same historic greats as did Galton and
Cox, but from a completely different orientation. As a cultural
anthropologist, Kroeber maintained that, in Simonton's words, "culture
takes primacy over the individual in any account of human (behavior),
and that historic geniuses are no exception..."
To prove his thesis, Kroeber collected "long lists of
notable figures from several nationalities and historic eras", and then
grouped them within a field and a shared cultural context, e.g.,
"Configuration for American Literature".
Then within these groupings he listed his notables in "strict
chronological order", identifying the most eminent figures by using
capital letters for their surnames (e.g. EMERSON, LONGFELLOW, POE,
WHITMAN, etc. in above configuration).
Kroeber found that genius never appeared in isolation, but
rather, in Simonton's words, that "one genius cluster(ed) with others of
greater and lesser fame in adjacent generations". He also found that
there were historical "crests" and "troughs" in every field. These fluctuations in the appearance of genius were much too rapid to
be explained by the simple mechanism of genetic inheritance along family
lines.
Kroeber argued, in Simonton's words, that his
"configurations" were due to "emulations": "Geniuses cluster in history
because the key figures of one generation emulate those in the
immediately preceding generations... (until) it attains a high point of
perfection that stymies further growth". At this point the "tradition
degenerates into empty imitation, as most creative minds move on to
greener pastures".
Recent research is consistent with these explanations; but many aspects of the developmental process from birth to the
attainment of greatness remain unaccounted for by Kroeber's
anthropological approach.
Developmental approaches
Retrospective studies, involving extensive interviews with
individuals who have attained eminence, or at least exceptional levels
of achievement, have added much to our understanding of the
developmental process. Two studies in particular stand out.
Scientific Elite – Zuckerman (1977)
Harriet Zuckerman's Scientific Elite: Nobel Laureates in the United States,
is based on many sources of research evidence, including a series of
forty-one extended interviews with American winners of the Nobel Prize for science.
Zuckerman reported her results around two main topics: How
the Prize is Awarded, and Career Development of the Scientific Elite.
Her findings on the first topic are briefly overviewed in the Wikipedia
article regarding the Nobel Prize
In relation to the question of the career development of
the scientific elite
Zuckerman uses the phrase "accumulation of advantage" to describe her
findings. In her words: "Scientists who show promise early in their
careers (are) given greater opportunities in the way of research
training and facilities. To the extent that these scientists are as
competent as the rest or more so, they ultimately will do far better in
terms of both role performance and reward... rewards (which) can be
transformed into resources for further work... (and hence over time)
scientists who are initially advantaged gain even greater opportunities
for further achievement and rewards."
To see if 'accumulation of advantage' was operating in the
career development of the scientific elite, Zuckerman compared the
careers of future laureates with those of "members of the United States National Academy of Sciences
and the scientific rank and file" along a number of dimensions
including socioeconomic origins, status of undergraduate and graduate
education, the process of moving into the scientific elite, and first
jobs and professorships.
She also interviewed forty-one Nobel laureates extensively
about their "apprenticeships" to "master" scientists while they were
doing their doctoral research, and other aspects of their career
development related to the above topics.
Zuckerman concluded that evidence of "accumulative of
advantage" was clearly present over the course of development, with
result that her research "... cast(s) considerable doubt on the
conclusion that marked differences in performance between the
ultra-elite and other scientists reflect equally marked differences in
their initial capacities to do scientific work".
Developing Talent in Young People – Bloom (1985)
Benjamin Bloom
and five colleagues conducted extensive interviews with 120 "young men
and women (as well as their parents and influential teachers)... who had
reached the highest levels of accomplishment" in six fields – Olympic
sprint swimmers, Top 10 rated professional tennis players, concert
pianists, accomplished sculptors, exceptional mathematicians, and
outstanding research neurologists.
They report many findings relevant to the "talent development process", including:
Development was tied throughout to the
values, interests, resources, and personal investments of the family of
origin. In most families "introduction to the field and initial... skill
development occurred" because the "(p)arents (or other family members),
in pursuing their own interests, created situations that intrigued,
interested, or involved the child... The child's interest was rewarded
or encouraged..." and the parents then provided other ways to extend
this interest.
The "work ethic"
is central to talent development. It is developed by "the home
environment" and "...directly related to learning and participation in
the chosen talent field".
"Each group of parents strongly encouraged their
children's development in a particularly highly approved talent field
(related to the parents' own "special interests") and gave much less
support to other possible talent fields and activities."
"Families and teachers were crucial at every point along
the way to excellence... what families and teachers do at different
times and how they do it clearly sets the stage for exceptional learning
in each talent field".
"Few... (of the) individuals (included in this study) were
regarded as child prodigies"; and, as a result, this research "raises
(serious) questions about earlier views of special gifts and innate
abilities as necessary prerequisites of talent development".
Recent approaches
A 1995 book by Hans Eysenck argues that a "personality trait" called Psychoticism
is central to becoming a creative genius; and a more recent book by
Bill Dorris (2009) looks at the influence of "everything from genetics
to cultural crises", including chance, over the course of development of
those who attain greatness. See – Hans Eysenck, Genius: The Natural History of Creativity
(1995), "construct(s)... a model of genius and creativity" whose
"novelty lies in (its) attempt to make personality differences central
to the argument".
In particular Eysenck is interested in a personality trait
called "psychoticism ... chief among (whose) cognitive features is a
tendency to over-inclusiveness, i.e., an inclination not to limit one's associations to relevant ideas, memories, images, etc."
He considers a massive range of experimental psychological
research in order to establish the underlying genetic, neuro-chemical
mechanisms which may be operating to influence levels of creativity
associated with fluctuations in "the tendency towards over-inclusiveness
indicative of psychoticism..."
Eysenck's assessment of his overall argument is as
follows: "There is no hint that the theory is more than a suggestion of
how many disparate facts and hypotheses can be pulled together into a
causal chain, explaining... the apogee of human endeavour – genius. If
the theory has one point in its favour it is that every step can be
tested experimentally, and that many steps have already received
positive support from such testing."
The Arrival of The Fittest
Bill Dorris's book, The Arrival of The Fittest: How The Great Become Great
(2009), attempts to address a number of issues which remain unanswered
on the subject. These include the role of chance over the course of
development, the importance of the development of unique personal
characteristics to achieving greatness, and the influence of changes in
the wider worlds surrounding the person – from interpersonal to societal
- on the course of an individual's development.
Dorris argues that those who attain 'greatness' are
credited with solving a key generational problem in a field and/or
society (e.g., Albert Einstein resolving the conflict between Isaac Newton and James Clerk Maxwell in physics at the outset of the 20th century; or Woody Guthrie providing a voice for the outcasts of the Great Depression of the 1930s).
Dorris's core argument is that those who become 'great'
start out with sufficient genetic potential and then are able, over two
or more decades, to obtain matches/fits with "the right kind of
problems" to extend the development of these genetic biases into what
Dorris terms, "key characteristics". These are the intellectual,
personality, and self characteristics which eventually turn out to be
required to solve a key generational problem in their field and/or
society.
Dorris argues that there are four types of matching
processes which occur over the course of such development. These refer
to matches between the developmental needs of the person and the
opportunities and resources essential to engaging in problem solving
activities that stimulate further development of those aspects of
intelligence, personality, and self which eventually become key
characteristics.
Two of these matching processes are covered extensively in
the existing research literature: continuous matching and cumulative
matching.
The other two of the matching processes described by
Dorris are completely new to this book: catalytic matching and chaotic
matching.
Dorris's argument in relation to catalytic matching is
that anyone who eventually becomes a 'great' will have experienced one
or more sustained periods of exceptionally accelerated development of
their key characteristics, accelerations which serve massively to
differentiate them from their former peers in terms of both development
and visibility within the field.
This acceleration occurs because the person becomes the
focal point (star) of a self-reinforcing system of expertise and
resources (catalytic system) which thrives off this person's accelerated
development and visibility.
Dorris's argument in relation to chaotic matching is that
access to the resources and learning opportunities essential to the
development of key characteristics of an eventual 'great' often occurs
not due to the efforts/planning of the individual, but simply due to
chance events in the interpersonal, institutional or societal worlds
around the person, who (unlike perhaps millions of equally capable
peers) becomes the beneficiary of these chance events – events which
Dorris argues can change a person's entire future in much the same way
as a lottery jackpot or a Titanic ticket.
A child using their fingers to make a small, circular hole in the sand
Child development involves the biological, psychological and emotional changes that occur in human beings between birth and the conclusion of adolescence. It is—particularly from birth to five years— a foundation for a prosperous and sustainable society.
Childhood is divided into three stages of life which include early childhood, middle childhood, and late childhood (preadolescence). Early childhood typically ranges from infancy to the age of 6 years old. During this period, development
is significant, as many of life's milestones happen during this time
period such as first words, learning to crawl, and learning to walk.
Middle childhood/preadolescence or ages 6–10 universally mark a
distinctive period between major developmental transition points. Adolescence often begins around the onset of puberty, marked as menarche or spermarche, occurring between 10 and 12 years of age, and ends upon acquiring the age of maturity. Adolescence is characterized by maturation of the body, increase in capacity for learning, and emergence of personal identity. Developmental change may occur as a result of genetically controlled processes, known as maturation, or environmental factors and learning, but most commonly involves an
interaction between the two. Development may also occur as a result of
human nature and of human ability to learn from the environment.
There are various definitions of the periods in a child's
development, since each period is a continuum with individual
differences regarding starting and ending. Some age-related development
periods with defined intervals include: newborn (ages 0–2 months); infant (ages 3–11 months); toddler (ages 1–2 years); preschooler (ages 3–4 years); prime childhood (ages 5–8 years); preteens (ages 9-12 years); and teens (ages 13–19 years).
Parents play a large role in a child's activities,
socialization, and development; having multiple parents can add
stability to a child's life and therefore encourage healthy development. A parent-child relationship with a stable foundation creates room for a
child to feel both supported and safe. This environment established to
express emotions is a building block that leads to children effectively
regulating emotions and furthering their development. Another influential factor in children's development is the quality of their care. Child-care programs may be beneficial for childhood development such as learning capabilities and social skills.
The optimal development of children is considered vital to
society and 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,
especially with regard to practices that promote development within the
school systems. Some theories seek to describe a sequence of states that
compose child development.
Also called "development in context" or "human ecology" theory, ecological systems theory was originally formulated by Urie Bronfenbrenner.
It specifies four types of nested environmental systems, with
bi-directional influences within and between the systems; they are the
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.
Jean Piaget was a Swiss scholar who began his studies in intellectual development
in the 1920s. Interested in the ways animals adapt to their
environments, his first scientific article was published when he was 10
years old, and he pursued a Ph.D. in zoology, where he became interested
in epistemology. Epistemology
branches off from philosophy and deals with the origin of knowledge,
which Piaget believed came from Psychology. After travelling to Paris,
he began working on the first "standardized intelligence test" at Alfred
Binet laboratories, which influenced his career greatly. During this
intelligence testing he began developing a profound interest in the way
children's intellectualism works. As a result, he developed his own
laboratory, where he spent years recording children's intellectual
growth and attempting to find out how children develop through various
stages of thinking. This led Piaget to 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 schemas and adaption occurs through assimilation and accommodation.
In the first stage in Piaget's theory, 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,
meaning 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, and 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, around age 2)
During this stage, young children begin analyzing their
environment using mental symbols, including words and images; the child
will begin to apply these 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 that 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,
pretending to be people they are not, for example teachers or
superheroes; they sometimes use different props to make this pretend
play more real. Some weaknesses in this stage are that children who are about 3–4 years old often display what is called egocentrism,
meaning the child is not able to see someone else's point of view, and
they feel as if every other person is experiencing the same events and
feelings that they are. 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, though they do not yet use rational thinking.
Concrete: (about first grade to early adolescence)
In this stage, children between the age of 7 and 11 use
appropriate logic to develop cognitive operations and begin applying
this new way of thinking to different events they encounter. Children in this stage incorporate inductive reasoning, which involves drawing conclusions from other observations in order to make a generalization. Unlike in the preoperational stage, children can now change and
rearrange mental images and symbols to form a logical thought, an
example of this is "reversibility", where the child now knows to reverse
an action by doing the opposite.
Formal operations: (around 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 strengths during this time are that the child or adolescent begins
forming their identity and begins understanding why people behave the
way they behave. While some weaknesses include the child or adolescent
developing some egocentric thoughts, including 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 themselves 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, bad
things only happen to other people.
Vygotsky, a Russian theorist, proposed the sociocultural
theory of child development. 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 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, called
"scaffolding", builds new knowledge onto the knowledge children already
have to help the child learn. An example of this might be when a parent "helps" an infant clap or roll their hands to the pat-a-cake rhyme, until they can clap and roll their hands themself.
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 that
during periods of crisis there was a qualitative transformation in the
child's mental functioning.
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.
Bowlby's observations led him to believe that close emotional bonds or
"attachments" between an infant and their primary caregiver were an
important requirement for forming "normal social and emotional
development".
Erikson, a follower of Freud, synthesized his theories with Freud's to create what is known as the "psychosocial"
stages of human development. Spanning from birth to death, they focus
on "tasks" at each stage that must be accomplished to successfully
navigate life's challenges.
John B. Watson's behaviorism theory forms the foundation of the behavioral model of development. Watson explained human psychology through the process of classical conditioning, and he believed that all individual differences in behavior were due to different learning experiences. He wrote extensively on child development and conducted research, such as the Little Albert experiment, which showed that a phobia could be created by classical conditioning. Watson was instrumental in the modification of William James' stream of consciousness approach to construct behavior theory. He 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 animals in a controlled situation and proved
that behaviors are influenced by the environment. Furthermore, he used
reinforcement and punishment to shape the desired behavior. Children's
behavior can strongly depend on their psychological development.
Sigmund Freud divided development, from infancy onward, into five stages. In accordance with his view that the sexual drive is a basic human motivation, each stage centered around the gratification of the libido within a
particular area, or erogenous zone, of the body. He argued that as
humans develop, they become fixated on different and specific objects
throughout their stages of development. Each stage contains conflict which requires resolution to enable the child to develop.
Other
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. This 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". These five domains are each crucial for survival, and prepare us to
develop key aspects of early cognition, they are: physical, numerical,
linguistic, psychological, and biological.
Beginning of cognition
The most influential theories emphasize social
interaction's essential contribution to child development from birth
(e.g., the theories of Bronfenbrenner, Piaget, Vygotsky).
It means that organisms with simple reflexes begin to cognize the
environment in collaboration with caregivers. However, different
viewpoints on this issue - the binding problem and the primary data entry problem - challenge the ability of children in this stage of development to meaningfully interact with the environment.
Recent advances in neuroscience and wisdom from physiology
and physics studies reconsider the knowledge gap on how social
interaction provides cognition in newborns and infants. Developmental
psychologist Michael Tomasello contributed to knowledge about the origins of social cognition in children by developing the notion of Shared intentionality. He posed ideas about unaware processes during social learning after birth to explain processes in shaping Intentionality. Other researchers developed the notion, by observing this collaborative interaction in psychophysiological research.
This concept has been expanded to the intrauterine period. Research professor in bioengineering at Liepaja University Igor Val Danilov developed the idea of Michael Tomasello by introducing a Mother-Fetus Neurocognitive model: a hypothesis of neurophysiological processes occurring during Shared intentionality. It explains the onset of childhood development, describing this
cooperative interaction at different levels of bio-system complexity,
from interpersonal dynamics to neuronal interactions. The Shared intentionality
hypothesis argues that nervous system synchronization provides
non-local neuronal coupling in a mother-child pair, contributing to the
proper development of the child's nervous system from the embryo onward. From the cognitive development perspective, this non-local neuronal
coupling enables the mother to indicate the relevant sensory stimulus of
an actual cognitive problem to the child, helping the child to grasp
the perception of the object. This prerequisite of Shared intentionality, the pre-perceptual
multimodal integration, succeeds owing to neuronal coherence in the
mother-fetus biosystem beginning from pregnancy. These cognitive-reflex and emotion-reflex stimuli conjunctions further
form innate neuronal assemblies, shaping the cognitive and emotional
neuronal patterns in statistical learning that, as empirical evidence
has shown, are continuously connected with the neuronal pathways of
reflexes. The natural neurostimulation of the mother's heart on the embryonal
nervous system ensures the balanced architecture of the nervous system
with the necessary cognitive functions corresponding to the ecological
context. Electromagnetic properties of the mother's heart and its interaction
with the mother's own and fetal nervous system (physical laws of
electromagnetic interference) form neuronal coherence in the
mother-fetus bio-system, providing the template beginning from
pregnancy.
A growing body of evidence in neuroscience supports the Shared intentionality
approach. Hyperscanning research studies show inter-brain coordinated
activity under conditions without communication in pairs while subjects
are solving a shared cognitive task This increased inter-brain activity is observed in pairs, which differs
from the result in the condition where subjects solve a similar task
alone. The significance of this knowledge is that although Shared intentionality
enables social cooperation to be achieved in the unaware condition
(unconsciously), it constitutes society. While this social interaction
modality facilitates child development, it also contributes to grasping
social norms and shaping individual values in children.
Continuity and discontinuity
Although the identification of developmental milestones is
of interest to researchers and caregivers, many aspects of development
are continuous and do not display noticeable milestones. Continuous 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.
These stages are periods of time, often associated with known age
ranges, 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 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 stages, he 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.
Although developmental change runs parallel with chronological age, age itself cannot cause development. The basic causes for developmental change are genetic 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 children
can survive 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 way the environment guides development is through
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 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 two eyes, and the experience of a
single three-dimensional image rather than the two-dimensional images
created by each eye, depends 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 alone.
In addition to plasticity, 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 interact with the environment
to make certain experiences more likely to occur. 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
produced 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 protected more and challenged less than a child without Down syndrome. 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 increase athletic skills, but may forgo music lessons.
In all of these cases, it becomes difficult to know whether the child's
characteristics were shaped by genetic factors, by experiences, or by a
combination of the two.
Asynchronous development
Asynchronous development occurs in cases when a child's
cognitive, physical, and/or emotional development occur at different
rates. This is common for gifted children when their cognitive
development outpaces their physical and/or emotional maturity, such as
when a child is academically advanced and skipping school grade levels
yet still cries over childish matters and/or still looks their age.
Asynchronous development presents challenges for schools, parents,
siblings, peers, and the children themselves, such as making it hard for
the child to fit in or frustrating adults who have become accustomed to
the child's advancement in other areas.
Research issues and methods
Research questions include:
What develops? What relevant aspects of the individual change over a period of time?
What are the rate and speed of development?
What are the mechanisms of development – what aspects of experience and heredity cause developmental change?
Are there typical individual differences in the relevant developmental changes?
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. Observational research may be followed by correlational
studies, which collect information about chronological age and some
type of development, such as increasing vocabulary; such studies examine
the characteristics of children at different ages. Other methods may include longitudinal studies, in which a group of children is re-examined on a number of occasions as they get older; cross-sectional studies,
where 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 that examine the effects of experience or
heredity by comparing characteristics of different groups of children
cannot use a randomized design;
while other studies use randomized designs to compare outcomes for
groups of children who receive different interventions or educational
treatments.
Infant research methods
When conducting psychological research on infants and children, certain key aspects need to be considered. These include that infants cannot talk, have a limited behavioral
repertoire, cannot follow instructions, have a short attention span, and
that, due to how rapidly infants develop, methods need to be updated
for different ages and developmental stages.
High-amplitude sucking technique (HAS) is a common way to
explore infants' preferences, and is appropriate from birth to four
months since it takes advantage of infants' sucking reflex. When this is being measured, researchers will code a baseline sucking
rate for each baby before exposing them to the item of interest. A
common finding of HAS shows a relaxed, natural sucking rate when exposed
to something the infant is familiar with, like their mother's voice,
compared to an increased sucking rate around novel stimuli.
The preferential-looking technique was a breakthrough made by Robert L. Fantz in 1961. In his experiments, he would show the infants in his study two
different stimuli. If an infant looks at one image longer than the
other, there are two things that can be inferred: the infant can see
that they are two different images and that the infant is showing
preference to one image in some capacity. Depending on the experiment,
infants may prefer to look at the novel and more interesting stimulus or
they may look at the more comforting and familiar image.
Eye tracking
is a straightforward way of looking at infants' preferences. Using an
eye tracking software, it is possible to see if infants understand
commonly used nouns by tracking their eyes after they are cued with the
target word.
Typical pattern of habituation
Another unique way to study infants' cognition is through habituation, which is the process of repeatedly showing a stimulus to an infant until they give no response. Then, when infants are presented with a novel stimulus, they show a
response, which reveals patterns of cognition and perception. Using this study method, many different cognitive and perceptual ideas
can be studied. Looking time, a common measure of habituation, is
studied by recording how long an infant looks at a stimulus before they
are habituated to it. Then, researchers record if an infant becomes dishabituated to a novel stimulus. This method can be used to measure preferences infants, including preferences for colors, and other discriminatory tasks, such as auditory discrimination between different musical excerpts.
Another way of studying children is through brain imaging technology, such as Magnetic Resonance Imaging (MRI), electroencephalography (EEG). MRI can be used to track brain activity, growth, and connectivity in children, and can track brain development from when a child is a fetus. EEG can be used to diagnose seizures and encephalopathy, but the
conceptual age of the infant must be considered when analyzing the
results.
Ethical considerations
Most of the ethical challenges that exist in studies with adults also exist in studying children, with some notable differences. Namely informed consent,
as while it is important that children consent to participate in
research, they cannot give legal consent; parents must give informed
consent for their children. Children can informally consent though, and
their continued agreement should be reliably checked for by both verbal
and nonverbal cues throughout their participation. Also, due to the
inherent power structure in most research settings, researchers must
consider study designs that protect children from feeling coerced.
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. These
milestones, and the chronological age at which they typically occur,
have been established via study of when various developmental tasks are
accomplished. However, there is considerable variation in when
milestones are reached, even between children developing 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 delayed development
of age-specific developmental milestones. Preventing, and intervening
early, in developmental delays is a significant topic in the study of
child development. Developmental delays are characterized by comparison
with age variability of a milestone, not with respect to average age at
achievement.
Physical aspects of development
Physical growth
For North American, Indo-Iranian (India, Iran), and European ...
Physical growth in stature and weight occurs for 15–20 years following birth, as the individual changes from the average weight of 3.5kg (7.7lb) and length of 50cm (20in) at full term birth to their final adult size. As stature and weight increase, 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. In a book directed toward pediatricians it says a 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.
Development from childhood to the end of puberty, from The Adolescent Period
Development of a boy from 10 to 17 years old
Development of a girl from 4 to 16 years old
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 1 year, but not quadrupled until 2 years. Growth then proceeds at a slow rate until a period of rapid growth occurs shortly before puberty (between
about 9 and 15 years of age). Growth is not uniform in rate and timing across all parts of the body.
At birth, head size is already relatively near that of an adult, but the
lower parts of the body are much smaller than adult size. Thus during
development, the head grows relatively little, while the torso and limbs
undergo a great deal of growth.
Mechanisms of change
Genetic factors play a major role in determining the
growth rate, particularly in the characteristic changes in proportions
during early human development. However, genetic factors can produce
maximum growth only if environmental conditions are adequate, as poor
nutrition, frequent injury, or disease can reduce the individual's adult
stature; though even 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 can be considerable. Some of these differences are due to
genetic or environmental factors, but individual differences in
reproductive maturation strongly influence development at some points. For individuals falling outside these typical variations, 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 weight gain. A similar term, stunted growth, generally refers to reduced growth rate as a manifestation of malnutrition in early childhood.
Motor skills
A child learning to walk
Physical abilities change through childhood from the
largely reflexive (unlearned, involuntary) movement young infants 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: basic skills necessary for everyday
life and recreational skills, including skills for employment or
interest based skills.
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. Movement ability develops 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. 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, timed inhibition and switching), which
are generally considered essential to motor skills, though some argue the reverse dependence—that motor skills are actually precursors to executive function.
Mechanisms
The mechanisms involved in motor development involve some
genetic components that determine aspects of muscle and bone strength,
as well as the physical size of body parts at a given age. 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 relationship between
coordination and limb growth in infants, genetic components have a huge
impact on motor development. Intra-limb correlations, like the distance between hip and knee joints,
were studied and proved to affect the way an infant will walk. There
are also genetic factors like the tendency to use the left or right side
of the body more (which allows for early prediction of the dominant
hand early). Sample t-tests
showed that, for female babies, there was a significant difference
between the left and right sides at 18 weeks and that the right side was
usually dominant. Some factors are biological constraints that we cannot control, like
male infants tending to have larger and longer arms, yet have an
influence on measures like when an infant's reach. Overall, there are
both sociological and genetic factors that influence motor development.
Nutrition and exercise also determine strength, flexibility, and the ease and accuracy with which a body part can be moved. It has also been shown that the frontal lobe
develops posterio-anteriorally (from back to front), which is
significant in motor development because the hind portion of the frontal
lobe is known to control motor functions. This form of development
(known as "Proportional Development") explains why motor functions
typically develop relatively quickly during childhood, while logic,
which is controlled by the middle and front portions of the frontal
lobe, usually will not develop until late childhood or 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 Climates are autonomy-supportive climates that a teacher can
adopt to as a suggested successful learning environment for children to
promote and reinforce motor skills by their own motivation. This
promotes participation and active learning in children, which Piaget's theory of cognitive development says is extremely important in early childhood.
Individual differences
Individual differences in motor ability are common and
depend partly on the child's weight and build. Infants with smaller,
slimmer, and more mature builds (proportionally) tend to crawl and crawl
earlier than infants with larger builds. Infants with more motor experience have been shown to belly crawl and
crawl sooner. Not all infants belly crawl; however, those who skip stage
this are not as proficient in their ability to crawl on their hands and
knees. After the infant period, individual differences are strongly affected
by opportunities to practice, observe, and be instructed on specific
movements. Atypical motor development such as persistent primitive reflexes 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 with trade-off in complex tasks. Encouraging children to participate
in activities that cater to their unique personalities is an effective
way to help them develop new skills and grow in different environments.
Children can learn valuable discipline, dedication, and socialization
lessons by challenging themselves to try new things. For example, a
naturally shy child may benefit from participating in a drama club,
where they can learn to express themselves confidently in front of
others. Similarly, a naturally competitive child may thrive in a sports
team where they can understand the value of teamwork and sportsmanship.
By embracing their individual personalities and interests, children can
develop into well-rounded, confident individuals with diverse skills and
experiences.
Organized sports can provide a child numerous opportunities to develop
essential life skills, such as leadership and teamwork. By being a part
of a team, a child can learn the value of working together towards a
common goal and understand that individual success is not the sole
focus. They can practice thinking beyond themselves and learn the
importance of considering the needs of others. Through playing sports,
children can develop a strong sense of responsibility, accountability,
and respect for their teammates, coaches, and opponents. Overall,
organized sports can offer a fun and enriching experience while helping
children build character and valuable life skills they can carry into
adulthood.
Based on personal experience, working during adolescence provided an
opportunity to develop time management skills and accountability.
Balancing schoolwork and employment required effective time allocation
and punctuality while being responsible enough to communicate with
managers regarding school-related conflicts. These essential practices
have influenced numerous people in how they are shaped in adulthood.
Children with disabilities
Children with Down syndrome or developmental coordination disorder are late to reach major motor skills milestones like sucking, grasping, rolling, sitting up and walking, talking. Children with Down syndrome sometimes have heart problems, frequent ear infections, hypotonia, or undeveloped muscle mass. Children can also be diagnosed with a learning disability,
which are disabilities in any of the areas related to language,
reading, and mathematics, with basic reading skills being the most
common learning disability. The definition of a learning disability
focuses on the difference between a child's academic achievement and
their 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 which allow them 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 play a role in practiced voluntary movements, such
as the use of the foot to dribble a soccer ball or the hand to dribble a
basketball.
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,
the responsiveness of parents, love, daily experiences, and physical
activity can influence early brain development of children. However, although it is assumed that the brain
causes cognition, it is not yet possible to measure specific brain
changes and show the cognitive changes they cause. Developmental
advances in cognition
are also related to experience and learning, especially 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
there are no large differences. Delays in cognitive development are problematic for children in
cultures that demand advanced cognitive skills for work and for
independent living. Everyday cognitive skills include problem-solving, reasoning, and abstract thinking among many others. In the absence of these life skills,
children may struggle to complete work in a timely manner or understand
certain tasks they are asked to do. If a delay is noticed screenings
can possibly find the source of the issue; if there is no underlying issue it is important to help aid the child
by reading with them, playing games with them, or reaching out to
professionals that can help.
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 them. Some differences are seen in fluid reasoning and visual processing, as
until about the age of four girls outperform boys in tests of these
skills, but by about six or seven boys and girls score similarly. This
is also true of IQ tests where girls tend to outscore boys, but again, as they age the gap lessens. Differences in cognitive achievement between different ethnic groups
appears to result from cultural or other environmental 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, as this
usually occurs during social interactions it is called a "social smile". By about 8–12 months, they go through a fairly rapid change and become fearful of perceived threats. By around 6–36 months, infants begin to prefer familiar people and show
anxiety and distress when separated from them, and when approached by
strangers.
Separation anxiety is a typical stage of development to an extent. Kicking, screaming, and throwing temper tantrums are normal symptoms of separation anxiety. The level of intensity of these symptoms can help determine whether or not a child has separation anxiety disorder, which is when a child constantly and intensely refuses to separate from the parent.
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 experiences of
emotion. Sexual and romantic emotions develop in connection with physical maturation.
Mechanisms
Genetic factors appear to regulate some of the
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 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 than girls, or if customs learned
by children of one ethnic group are different than those learned by
another. Social and emotional differences between boys and girls of the same age
may also be associated with the differences in the timing of puberty seen between the two sexes.
Language serves the purpose of communication to express
oneself through a systematic and conventional use of sounds, signs, or
written symbols. There are four subcomponents a child must know to acquire language
competence: phonology, lexicon, morphology and syntax, and pragmatics. These subcomponents combine to form the components of language: sociolinguistics and literacy. Currently, there is no single accepted theory of language acquisition
but various explanations of language development have been given.
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 frequency and accuracy of production of various vowels and
consonants, the acquisition of phonemic contrasts and distinctive
features, or by viewing development in regular stages and to
characterizing systematic strategies they adopt.
Lexicon is similar to vocabulary as they both describe the complex dictionary of words used in speech production and comprehension. The lexicon of a language also includes that 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 words and how they are formed. Morphology is also the
branch of linguistics that deals with words, their internal structure
and how they are formed. It is also the mental system involved in word
formation.
Pragmatics is the study of the relationship between linguistic forms and speakers of the language, it also incorporates how speech is used to serve different functions.
Pragmatics 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 concepts by modifying a topic word. The third stage, between
two and three years old, involves the child using complete
subject-predicate structures to communicate concepts. Fourth, children
make changes on basic sentence structure that enables them to
communicate more complex concepts. 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 complicated syntactic relationships between
the ages of five years old to ten years old.
Sequential skills and milestones
Sequential skills 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; 2–3 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
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 "ma-ma" and "da-da". Around this age infants also 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 are 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, with
adolescents having smaller vocabularies than adults and experiencing
more difficulty with constructions such as the passive voice.
By age 1, children are able to say 1–2 words, respond to their name, imitate familiar sounds and follow simple instructions. Between 1–2 years old, the child uses 5–20 words, says 2-word
sentences, expresses their wishes by saying words like "more" or "up",
and understands the word "no". Between 2 and 3 years of age, the child is able to refer to themself as
"me", combine nouns and verbs, use short sentences, use some simple
plurals, answer "where" questions, and has a vocabulary of about 450
words. By age 4, children are able to use sentences of 4–5 words and have 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, up to 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 birthday. 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 earlier than previously thought.
Vocabulary typically grows from about 20 words at 18
months to around 200 words at 21 months. Starting around 18 months the
child begins to combine words into two-word sentences, which the adult
typically expands to clarify its 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 age three the child begins to use complex sentences, including relative clauses, although they are 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 narratives 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, a child
needs to learn to combine their perspective with that of others and with
outside events and learn to use linguistic indicators to show they are
doing this. They also learn to adjust their language depending on who
they are speaking to. 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.
Theories
Although the role of adult speech is important in
facilitating the child's learning, there is considerable disagreement
among theorists about the extent to which it influences children's early
meanings and expressive words. Findings about the initial mapping of
new words, the ability to decontextualize words, and refine meaning of
words are diverse. One hypothesis, known as the syntactic bootstrapping
hypothesis, refers to the child's ability to infer meaning from cues by
using grammatical information from the structure of sentences.
Another theory is the multi-route model which argues 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 said 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 say that universal grammar is innate and language experience activates that innate knowledge. Social interactionist theories define language as a social phenomenon
where 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 correlation with their social
cognitive interpretation and their understanding of the speakers'
intended meanings. Connectionist theory is a pattern-learning procedure that defines
language as a system composed of smaller subsystems or patterns of sound
or meaning. Behaviorist theories defined language as the establishment of positive reinforcement, but are now regarded as only being of historical interest.
Communication
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 directions should, in
theory, be followed. In the case of young 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 children to recognize the other speaker's
emotions.
Communicative language is both verbal and nonverbal,
and to achieve communication competence, four components must be
mastered. These components are: grammatical competence, including
vocabulary knowledge, rules of word sentence formation, etc.;
sociolinguistic competence, or the appropriate meanings and grammatical
forms in different social contexts; discourse competence, which is
having the knowledge required to combine forms and meanings; and
strategic competence in the form of knowledge about 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
relies more heavily on gestures and body movements 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 are 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 the use of communicative gestures begins,
including communicative pointing where an infant points to request
something, or to point to provide information. Another communicative gesture presents around the age of 10 and 11
months where infants start gaze-following, by looking where another
person is looking. This joint attention
results in changes to their social cognitive skills between the ages of
9 and 15 months as their time is increasingly spent with others. Children's use of non-verbal communicative gestures predicts 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 the words they learn are the words used for functional
meaning. This instigation of speech has been termed pragmatic bootstrapping.
According to this theory children view words as a means of social
connection, in that words are used to connect the communicative
intentions of the speaker to new words. Hence, the competence of verbal communication through language is achieved by gains in syntax or grammar.
Another function of communicating through language is related to pragmatic development. Pragmatic development includes the child's intentions of communication
before they 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 how to participate in conversations and how to relay past experiences/events (discourse knowledge), as well as learning how to use language appropriately for 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 the conversation.
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 advance to an equal temperament of conversation. This shift in balance of conversation suggests a development of narrative discourse in communication. Ordinarily, the development of communicative competence and the development of language are linked to one another.
Causes of delays
Individual differences
Delays in language skills are the most frequent type of
developmental delay. According to demographics 1 out of 6 children have a
significant language delay; speech/language delay is three to four times more common in boys than in girls. Some children 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 attention from the family.
It is 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.
There are many environmental causes that are linked to
language delays, including situations where the child has their full
attention on another skill, such as walking. The child may have a twin
or a sibling close to their own age and may not be receiving the
parent's full attention. Another possibility is that the child is in a
daycare with too few adults to administer individual attention. General
development can be impacted if the child does not receive an adequately
nutritional diet. Perhaps the most obvious environmental cause would be a child that
suffers from psychosocial deprivation such as poverty, poor housing,
neglect, inadequate linguistic stimulation, or emotional stress.
Neurological causes
Language delay can be caused by a substantial number of underlying disorders, such as intellectual disability,
which accounts for more than 50 percent of language delays. Language
delay is usually more severe than other developmental delays in
intellectually disabled children, and it is usually the first obvious
symptom of intellectual disability. Intellectual disability causes
global language delay, including delayed auditory comprehension and
delayed use of gestures.
Impaired hearing is another 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, and even the most minimum hearing impairment or auditory processing deficit
can considerably affect language development. Generally the more the
severe the impairment, the more serious the language delay. Nonetheless, 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 that represent the
sounds of speech. Children with dyslexia may encounter problems in
rhyming and separating the sounds that compose words, which is essential
in learning to read as early reading skills rely heavily on word recognition. When using an alphabetwriting 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. Difficulty
connecting the sounds of language to the letters of words may result
difficulty in understanding sentences. Confusion between similar
letters, such as "b" and "d" can occur. In general the symptoms of
dyslexia are: 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
is the most common sign of 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 types of language disorders are having limited to no verbal
speech, echolalia or repeating words out of context, problems responding to verbal instruction and ignoring people who speak to them directly.
Gender identity
involves how a person perceives themselves as male, female, or a
variation of the two. Children can identify themselves as belonging to a
certain gender as early as two years old, but how gender identity is developed is a topic of scientific debate.
Several factors are involved in determining an individual's gender,
including neonatal hormones, postnatal socialization, and genetic
influences. 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. People exposed
to high levels of testosterone during gestation typically develop a male
gender identity, while those not exposed to testosterone, or who lack
the receptors necessary to interact with it, typically develop a female
gender identity.
An individual's genes are also thought 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. It is unknown whether socialization plays a part in determining gender
identity postnatally. 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.
Race
In addition to the course of development, previous
literature has looked at how race, ethnicity, and socioeconomic status
has affected child development. Some studies seem to speak to the
importance of adult supervision of adolescent youth. Literature suggested that African American child development was
sometimes differentiated between cultural socialization and racial
socialization. Further, a different study found that most immigrant youth choose majors focusing on the fields of science and math.
Risk factors
Risk factors in child development include: malnutrition,
maternal depression, maternal substance use and pain in infancy; though
many more factors have been studied.
Although there are a large number of studies regarding the
effect of maternal depression and postnatal depression on various areas
of infant development, they are yet to come to a consensus regarding
the true effects. Numerous studies indicate impaired development, while
many others find no effect of depression on development.
A study of 18-month-olds whose mothers had depressive symptoms while the children were 6 weeks and/or 6 months old found that maternal depression had no effect on the child's cognitive development.
Furthermore, the study indicates that maternal depression combined with
a poor home environment is more likely to have an effect on cognitive
development than maternal depression alone. However, the authors
conclude that it may be that short term depression has no effect, but
long term depression could cause more serious problems.
A longitudinal study
spanning 7 years found no effect of maternal depression on cognitive
development as a whole, however it found that boys are more susceptible
to cognitive developmental issues when their mothers had depression.
This trend is continued in a study of children up to 2
years old, which revealed a significant difference on cognitive
development between genders, with girls having a higher score; however
girls scored higher regardless of the 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 IQ
test than peers with healthy mothers, while this difference is less
pronounced in girls. Three 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. Furthermore, 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 intonation, and tend to use unstructured vocal behaviours. Furthermore, compared to when interacting with healthy mothers, infants
interacting with depressed mothers show signs of stress, such as
increased pulse and raised cortisol levels, and make more use of avoidance behaviours, for example looking away. Mother-infant interaction at 2 months has been shown to affect the child's cognitive performance at 5 years.
Studies have begun to show that other forms of psychopathology
(mental illness) 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.
Research has provided conflicting evidence regarding the severity of effects on children's development posed by maternal substance use during and after pregnancy. Children exposed to cocaine in utero weigh less than those not exposed at ages ranging from 6 to 30 months. Additionally, studies indicate that the head circumference of children
exposed to cocaine is lower than those that of children without cocaine
exposure.However, two more recent studies found no significant differences in
either measure between those exposed to cocaine and those who were not.
Maternal cocaine use may also affect the child's cognitive development, with exposed children achieving lower scores on measures of psychomotor and mental development. Again though, there is conflicting evidence, and a number of studies
indicate no effect of maternal cocaine use on a child's cognitive
development.
Continuing the trend, some studies found maternal cocaine use to impair motor development,while others showed 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 can also affect an unborn child's cognitive and behavioral
development.
Smoking tobacco increases pregnancy complications including low birth weight, prematurity, placental abruption,
and intrauterine death. After birth it can disturb maternal-infant
interactions, reduce IQ, increase the risk of ADHD, and lead to tobacco
use in the child.
Prenatal marijuana
exposure may have long-term emotional and behavioral consequences, as
at ten-years-old children who had been exposed to the drug during
pregnancy reported more depressive symptoms than unexposed peers. Some
other effects include executive function impairment, reading difficulty,
and delayed emotional regulation.
An opiate drug, such as heroin, in utero decreases birth weight, birth length, and head circumference. Parental opiate exposure may impact the infant's central nervous system and autonomic nervous system,
though the evidence is even more inconsistent than with parental
cocaine exposure. There are also some unexpected negative consequences
on a child, such as: less rhythmic swallowing, strabismus, and feelings
of rejection.
Malnutrition and Undernutrition
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, later in life, poor social
relationships. 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 (11.88kg[26.2lb] compared to 14kg[31lb]), and were shorter (85.3cm[33.6in] versus 94cm[37in]).
Malnutrition during the first 1000 days of a child's life can cause irreversible physical and mental stunting. Infections and parasites related to poor sanitation and hygiene can impact absorption of nutrients in the gut. Adequate sanitation and hygiene (rather than just access to food) play a critical role in preventing undernutrition, malnutrition and stunting and ensuring normal early childhood development. Malnutrition has been indicated as a negative influence on childhood intelligence quotient (IQ). Although it has also been suggested that this effect is nullified when
parental IQ is considered, implying that this difference is genetic.
Specific nutrients
The effect of low iron levels on cognitive development and IQ has yet to reach consensus. Some evidence suggests that even 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.
Other nutrients have been strongly implicated in brain development, including iodine and zinc. Iodine is required for the formation 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. Zinc supplementation appears to be beneficial for growth in infants under six months old.
Socioeconomic status
Socioeconomic status is measured primarily based on income, educational attainment and occupation. Investigations into the role of socioeconomic factors on child development repeatedly show that continual poverty is more harmful on IQ, and cognitive abilities than short-term 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 these issues. Poverty can also cause a number of other factors shown to effect child
development, such as poor academic success, less family involvement,
iron deficiency, infections, a lack of stimulation, and malnutrition. Poverty also increases the risk of lead poisoning due to lead paint found on the walls of some houses; child blood levels of lead increase as income decreases. Income based 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, and children coming from households featuring continual or temporary
poverty perform lower than children in middle-class families.
Parental educational attainment is the most significant socioeconomic factor in predicting the child's cognitive abilities, as those with a mother with a 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.
On the other hand, maternal employment is associated with
slightly lower test scores, regardless of socioeconomic status.
Counterintuitively, maternal employment results in more disadvantages
the higher the socioeconomic status, as these children are being removed
from a more enriching environment to be put in child care,
though the quality of the child care must 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 with 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 that full-time work within the first year was correlated with
negative effects on 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 results. 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
households have greater economic vulnerability and less parental
involvement, leading to worse social, behavioral, educational, or
cognitive outcomes.
A child's academic achievement is influenced by parents' educational attainment, parenting style,
and parental investment in their child's cognitive and educational
success. Higher-income families are able to afford learning
opportunities both inside and outside the classroom. Poverty-stricken children have fewer opportunities for 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. If teachers perceive low-SES children as being less academically able
then they may provide them with less attention and reinforcement. On the other hand, when schools make an effort to increase 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 known to be a risk to child development. Intestinal parasitism is one of the most neglected tropical diseases in
the developed world, and harboring of this parasite could have several
health implications in children that negatively affect childhood
development and morbidity. Prolonged exposure to faecally-transmitted infections, including environmental enteropathy, other intestinal infections, and parasites during early childhood can lead to irreversible stunting. Reducing the prevalence of these parasites can be a benefit in child growth, development, and educational outcome.
Toxin exposure
High levels of lead in the blood is associated with attention deficits, while arsenic poisoning has a negative effect on both verbal IQ and on total intelligence quotient. 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
Intrauterine growth restriction is associated with learning deficits in childhood, and as such, is related to lower IQ. Cognitive development can also be harmed by childhood exposure to violence and trauma, including spousal abuse between the parents and sexual abuse.
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,
accounting for 78% of all child abuse cases in the United States in
2010 alone. Scientific studies show that 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, as if those levels are normal, one can,
by definition, conclude that a child is not being neglected. Measured
areas of development can include weight, height, stamina, social and
emotional responses, speech and motor development. As all these features
go into making a medical assessment of whether a child is thriving, a professional looking to start an assessment of neglect might start with information collected by a doctor.
Infants are often weighed and measured when seen by their pediatrician
for well-baby check-ups. The physician initiates a more complete
evaluation when the infant's development and functioning are found to be
delayed. Then 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 below
normal, the identification of neglect then requires the professional to
establish if this can be put down to the level of nurturance experienced
by the child. Developmental delays caused by genetic conditions or
disease need to be discounted, as they do not have their basis in a lack
of nurturance.
Starting the assessment
Besides routine pediatrician visits, another way of
starting the process of identifying neglect is to determine if the child
is experiencing a level of nurturance lower than that considered
necessary to support normal development, which might be unique to the child's age, gender and other factors. Exactly how to ascertain 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, determining whether a
child is getting the requisite level of nurturance needs to take into
account not just the intensity of the nurturance, but also the duration
and frequency of the nurturance.
Children may 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 must keep
detailed histories of care provision, which demonstrate the duration of
subnormal exposure to care, stimulation, and nutrition.
Common guidance suggests professionals should focus on the
levels of nurturance provided by the carers of the child, as 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 is sufficient to conclude that neglect is
occurring. One definition is that, "a child experiences neglect when the adults
who look after them fail to meet their needs", which clearly defines
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. This definition, 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. In practice,
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. While some guidance on identifying neglect urges
practitioners to measure developmental levels, other guidance focuses 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, as 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. The developmental delay may be caused by a mixture of
underexposure to nurture, abuse, genetics, and disease.
Measuring tools
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 that can be used by a practitioner to explore whether neglect
is taking place across a range of family functioning areas.
Intervention programs
Early intervention programs and treatments include
individual counselling, family and group counselling, social support
services, behavioural skills training programs to eliminate problematic
behaviour and teach parents appropriate parenting behaviour.
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 programme
is a preventive programme working with parents of children under 6
years old who are at risk of significant harm through neglect. The
programme is delivered in the home by trained practitioners, and is 18
to 20 sessions focused 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 number of child neglect cases.
