Play (activity)

From Wikipedia, the free encyclopedia

Playfulness by Paul Manship

Play is a range of voluntary, intrinsically motivated activities done for recreational pleasure and enjoyment.^[1 Play is commonly associated with children and juvenile-level activities, but play occurs at any life stage, and among other higher-functioning animals as well, most notably mammals. 

Many prominent researchers in the field of psychology, including Melanie Klein, Jean Piaget, William James, Sigmund Freud, Carl Jung and Lev Vygotsky have viewed play as confined to the human species, believing play was important for human development and using different research methods to prove their theories.

Play is often interpreted as frivolous; yet the player can be intently focused on their objective, particularly when play is structured and goal-oriented, as in a game. Accordingly, play can range from relaxed, free-spirited and spontaneous through frivolous to planned or even compulsive. Play is not just a pastime activity; it has the potential to serve as an important tool in numerous aspects of daily life for adolescents, adults, and cognitively advanced non-human species (such as primates). Not only does play promote and aid in physical development (such as hand-eye coordination), but it also aids in cognitive development and social skills, and can even act as a stepping stone into the world of integration, which can be a very stressful process. Play is something that most children partake in, but the way play is executed is different between cultures and the way that children engage with play varies universally.

Definitions

The seminal text in the field of play studies is the book Homo Ludens first published in 1944 with several subsequent editions, in which Johan Huizinga defines play as follows:

Summing up the formal characteristic of play, we might call it a free activity standing quite consciously outside 'ordinary' life as being 'not serious' but at the same time absorbing the player intensely and utterly. It is an activity connected with no material interest, and no profit can be gained by it. It proceeds within its own proper boundaries of time and space according to fixed rules and in an orderly manner. It promotes the formation of social groupings that tend to surround themselves with secrecy and to stress the difference from the common world by disguise or other means.

This definition of play as constituting a separate and independent sphere of human activity is sometimes referred to as the "magic circle" notion of play, a phrase also attributed to Huizinga. Many other definitions exist. Jean Piaget stated, "the many theories of play expounded in the past are clear proof that the phenomenon is difficult to understand."

There are multiple aspects of play people hone in on when defining it. One definition from Susanna Millar's The Psychology of Play defines play as: “any purposeful mental or physical activity performed either individually or group-wise in leisure time or at work for enjoyment, relaxation, and satisfaction of real-time or long term needs.” This definition particularly emphasizes the conditions and benefits to be gained under certain actions or activities related to play. Other definitions may focus on play as an activity that must follow certain characteristics including willingness to engage, uncertainty of the outcome, and productivity of the activity to society.

Another definition of play from the twenty-first century comes from the National Playing Fields Association (NPFA). The definition reads as follows: “play is freely chosen, personally directed, intrinsically motivated behaviour that actively engages the child.” This definition focuses more on the child's freedom of choice and personal motivation related to an activity.

Forms

People having fun

 

Play can take the form of improvisation or pretense, interactive, performance, mimicry, games, sports, and thrill-seeking, such as extreme or dangerous sports (sky-diving, high-speed racing, etc.). Philosopher Roger Caillois wrote about play in his 1961 book Man, Play and Games and Stephen Nachmanovitch expanded on these concepts in his 1990 book Free Play: Improvisation in Life and Art. Nachmanovitch writes that:

Improvisation, composition, writing, painting, theater, invention, all creative acts are forms of play, the starting place of creativity in the human growth cycle, and one of the great primal life functions. Without play, learning and evolution are impossible. Play is the taproot from which original art springs; it is the raw stuff that the artist channels and organizes with all his learning and technique. (Free Play, p. 42)

Free play gives children the freedom to decide what they want to play and how it will be played. Both the activity and the rules are subject to change in this form, and children can make any changes to the rules or objectives of the play at any time. Some countries in the twenty-first century have added emphasis of free play into their values for children in early childhood such as Taiwan and Hungary.

Structured play has clearly defined goals and rules and such play is called a "game". Other play is unstructured or open-ended. Both types of play promote adaptive behaviors and mental states of happiness.

Sports with defined rules will take place within designated play spaces, such as sports fields where, in Soccer for example, players kick a ball in a certain direction and push opponents out of their way as they do so. While appropriate within the sport's play space, these same behaviors might be inappropriate or even illegal outside the playing field.

Other designed play spaces can be playgrounds with dedicated equipment and structures to promote active and social play. Some play spaces go even farther in specialization to bring the play indoors and will often charge admission as seen at Children's Museums, Science Centers, or Family Entertainment Centers. Family Entertainment Centers (or Play Zones) are typically For-Profit businesses purely for play and entertainment, while Children's Museums and Science Centers are typically Non-Profit organizations for educational entertainment. 

The California-based National Institute for Play describes seven play patterns:

1. Attunement play, which establishes a connection, such as between newborn and mother.
2. Body play, in which an infant explores the ways in which his or her body works and interacts with the world, such as making funny sounds or discovering what happens in a fall.
3. Object play, such as playing with toys, banging pots and pans, handling physical things in ways that use curiosity.
4. Social play, play which involves others in activities such as tumbling, making faces, and building connections with another child or group of children.
5. Imaginative or pretend play, in which a child invents scenarios from his or her imagination and acts within them as a form of play, such as princess or pirate play.
6. Storytelling play, the play of learning and language that develops intellect, such as a parent reading aloud to a child, or a child retelling the story in his or her own words.
7. Creative play, by which one plays with imagination to transcend what is known in the current state, to create a higher state. For example, a person might experiment to find a new way to use a musical instrument, thereby taking that form of music to a higher plane; or, as Einstein was known to do, a person might wonder about things which are not yet known and play with unproven ideas as a bridge to the discovery of new knowledge.

Separate from self-initiated play, play therapy is used as a clinical application of play aimed at treating children who suffer from trauma, emotional issues and other problems.

Children

In young children, play is frequently associated with cognitive development and socialization. Play that promotes learning and recreation often incorporates toys, props, tools or other playmates. Play can consist of an amusing, pretend or imaginary activity alone or with another. Some forms of play are rehearsals or trials for later life events, such as "play fighting", pretend social encounters (such as parties with dolls), or flirting. Modern findings in neuroscience suggest that play promotes flexibility of mind, including adaptive practices such as discovering multiple ways to achieve a desired result, or creative ways to improve or reorganize a given situation (Millar, 1967; Shonkoff & Phillips, 2000).

Children playing in a sandbox

 

As children get older, they engage in board games, video games and computer play, and in this context the word gameplay is used to describe the concept and theory of play and its relationship to rules and game design. In their book, Rules of Play, researchers Katie Salen and Eric Zimmerman outline 18 schemas for games, using them to define "play", "interaction" and "design" formally for behaviorists. Similarly, in his book Half-Real: Video Games between Real Rules and Fictional Worlds, game researcher and theorist Jesper Juul explores the relationship between real rules and unreal scenarios in play, such as winning or losing a game in the real world when played together with real-world friends, but doing so by slaying a dragon in the fantasy world presented in the shared video game.

Play is explicitly recognized in Article 31 of the Convention on the Rights of the Child (adopted by the General Assembly of the United Nations, November 29, 1989), which declares:

• Parties recognize the right of the child to rest and leisure, to engage in play and recreational activities appropriate to the age of the child and to participate freely in cultural life and the arts.
• Parties shall respect and promote the right of the child to participate fully in cultural and artistic life and shall encourage the provision of appropriate and equal opportunities for cultural, artistic, recreational and leisure activities.

Children's Games, 1560, Pieter Bruegel the Elder

History of childhood playtime

American historian Howard Chudacoff has studied the interplay between parental control of toys and games and children's drive for freedom to play. In the colonial era, toys were makeshift and children taught each other very simple games with little adult supervision. The market economy of the 19th century enabled the modern concept of childhood as a distinct, happy life stage. Factory-made dolls and doll houses delighted young girls. Organized sports filtered down from adults and colleges, and boys learned to play with a bat, a ball and an impromptu playing field. In the 20th century, teenagers were increasingly organized into club sports supervised and coached by adults, with swimming taught at summer camps and through supervised playgrounds.^[ Under the New Deal's Works Progress Administration, thousands of local playgrounds and ball fields opened, promoting softball especially as a sport for all ages and both sexes. By the 21st century, Chudacoff notes, the old tension between parental controls and a child's individual freedom was being played out in cyberspace.

Cultural differences of play

Museum of toys – Portugal

 

The act of play time is a cross-cultural phenomenon that is universally accepted and encouraged by most communities however it can differ in the ways that is performed.

Some cultures, such as Euro-American cultural heritages, encourage play time in order to stress cognitive benefits and the importance of learning how to care for one's self. Other cultures, such as people of African American or Asian American heritages, stress more group oriented learning and play where kids can learn what they can do with and for others. Parent interactions when it comes to playtime also differs drastically within communities. Parents in the Mayan culture do interact with their children in a playful mindset while parents in the United States tend to set aside time to play and teach their children through games and activities. In the Mayan community, children are supported in their playing but also encouraged to play while watching their parents do household work in order to become familiar with how to follow in their footsteps.

Elephant – Mud play

 

All around the world, children use different natural materials like stones, water, sand, leaves, fruits, sticks and a variety of resources to play. In addition, there are groups that have access to crafts, industrialized toys, electronics and video-games.

In Australia, games and sports are part of play. There, play can be considered as preparation for life and self- expression, like in many other countries.

Groups of children in Efe of the Democratic Republic of Congo can be seen making ‘food’ from dirt or pretending to shoot bows and arrows much like their elders. These activities are similar to other forms of play worldwide. For instance, children can be seen comforting their toy dolls or animals, anything that they have modeled from adults in their communities.

In Brazil, we can find children playing with balls, kites, marbles, pretend houses or mud kitchens, like in many other countries. In smaller communities they use mud balls, little stones or cashews to replace marbles.

Child playing around the kitchen

 

At an indigenous community of Sierra Nevada de Santa Marta in Colombia, children's play is highly valued and encouraged by leaders and parents. They interact with the children of different ages and explore together different environments to let the children express themselves as part of the group.

Some children in the Sahara use clay figures as their forms of playful toys. Toys in general are a representation of cultural practices. They usually illustrate characters and objects of a community.

Play time can be used as a way for children to learn the different ways of their culture. Many communities use play to can emulate work. The way in which children mimic work through their play can differ according to the opportunities they have access to, but it is something that tends to be promoted by adults.

Sports

Sportive activities are one of the most universal forms of play. Different continents have their own popular/dominant sports. For example, European, South American, and African countries enjoy soccer (also known as ‘football’ in Europe), while North American countries prefer basketball, ice hockey, baseball, or American football. In Asia, sports such as table tennis and badminton are played professionally; however soccer and basketball are played amongst common folks. Events such as The Olympic Games and FIFA World Cup showcase countries competing with each other and are broadcast all over the world. Sports can be played as a leisure activity or within a competition. According to sociologist Norbert Elias; it is an important part of "civilization process". Victory and defeat in sports can also influence one's emotions to a point where everything else seems so irrelevant.^[23] Sport fans can also imagine what it feels like to play for their preferred team. The feelings people experience can be so surreal that it affects their emotions and behavior.

Benefits in youth

Youth sport can provide a positive outcome for youth development. Research shows adolescents are more motivated and engaged in sports than any other activity, and these conditions predict a richer personal and interpersonal development. Anxiety, depression and obesity can stem from lack of activity and social interaction. There is a high correlation between the amount of time that youth spend playing sports and the effects of physical (e.g., better general health), psychological (e.g., subjective well being), academic (e.g., school grades), and social benefits (e.g., making friends). Electronics over the past 10 years have been looked as a form of playtime but researchers have found that most electronic play leads to lack of motivation, no social interaction and can lead to obesity. Play is originally based on the idea of children using their creativity while developing their imagination, dexterity, physical, cognitive and emotional strength. Dramatic play is common in younger children. For the youth community to benefit from playtime, the following are recommended:

• Give children ample, unscheduled time to be creative to reflect and decompress
• Give children “true” toys, such as blocks or dolls for creativity
• Youth should have a group of supportive people around them (teammates, coaches, and parents) with positive relationships
• Youth should possess skill development; such as physical, interpersonal, and knowledge about the sport
• Youth should be able to make their own decisions about their sport participation
• Youth should have experiences that are on par with their certain needs and developmental level.  Research findings on benefits in youth

With regular participation in a variety of sports, children can develop and become more proficient at various sports skills (including, but not limited to, jumping, kicking, running, throwing, etc.) if the focus is on skill mastery and development.Young people participating in sports also develop agility, coordination, endurance, flexibility, speed, and strength. More specifically, young athletes could develop the following

• enhanced functioning and health of Cardiorespiratory and Muscular systems
• improved flexibility, mobility, and coordination
• increased stamina and strength
• increased likelihood of maintaining weight.

Moreover, research shows that regular participation in sport and physical activity is highly associated with lowering the risk of diabetes, heart disease, obesity, and other related diseases. Young people also tend to be more nutrition-conscious in their food choices when participating in sport Girls involved in sport tend associate with lower chance of teenage pregnancy, begin smoking, and/or developing breast cancer. Young athletes have shown lower levels of total cholesterol and other favorable profiles in serum lipid parameters associated with cardiovascular disease. Sport provides an arena for young people to be physically active and in result reduce the time spent in sedentary pursuits, such as watching TV and playing video games.

Adults

Playing weiqi in Shanghai

 

Although adults who engage in excessive amounts of play may find themselves described as "childish" or "young at heart" by less playful adults, play is actually an important activity, regardless of age. Creativity and happiness can result from adult play, where the objective can be more than fun alone, as in adult expression of the arts, or curiosity-driven science. Some adult "hobbies" are examples of such creative play. In creative professions, such as design, playfulness can remove more serious attitudes (such as shame or embarrassment) that impede brainstorming or artistic experimentation in design.

Imaginative play and role play may allow adult individuals to practice useful habits such as learned optimism, which is helpful in managing fear or terrors. Play also offers adults the opportunity to practice concepts that may not have been explicitly or formally taught (e.g. how to manage misinformation or deceit). Thus, even though play is just one of many tools used by effective adults, it remains a necessary one.

Workplace

There has been extensive research when it comes to the benefits of play amongst children, youth, and adolescence. Most commonly overlooked are the benefits of play for adults, more specifically, adults who spend a lot of time in the workplace. Many adults in North America are in the workforce and spend half of their waking hours in a workplace environment with little to no time for play. Play in this context refers to leisure-type activities with colleagues during lunch breaks or short breaks throughout the working day. Leisure activities could include, but are not limited to, different forms of physical sport activities, card games, board games, video games and interaction-based type video games, foosball, ping-pong, yoga, and boot-camp sessions. 

Research shows that playing games may promote a persistent and optimistic motivational style and positive affect. Positive affect enhances people's experiences, enjoyment, and sense of satisfaction derived from the activity, during their engagement with a certain task. While people are engaged in their work, positive affect increases the satisfaction they feel from the work, and this has also been shown to increase their creativity and improve their performance on problem-solving tasks as well as other tasks. The development of a persistent motivational style charged with positive affect may lead to lasting work success.

Studies show that work and play are mutually supportive. Employees need to experience the sense of newness, flow, discovery and liveliness that play provides. By doing this, it will provide the employee with the sense that they are integrated within the organization, and therefore they will feel and perform better. By incorporating play at work, it will also result in more productivity, creativity and innovation, higher job satisfaction, greater workplace morale, stronger or new social bonds, improved job performance, a decrease in staff turnover, absenteeism and stress. Decreased stress leads to less illness, which results in lower health care costs. Play at work may help employees function and cope when under stress, refresh body and mind, encourage teamwork, trigger creativity, and increase energy while preventing burnout.

Studies show that companies that encourage play at work, whether short breaks throughout the day or during lunch breaks experience more success because it leads to positive emotion amongst employees. Risk taking, confidence in presenting novel ideas, and embracing unusual and fresh perspectives are common characteristics associated with play at work. Play can increase self-reported job satisfaction and well-being. Employees experiencing positive emotions are more cooperative, more social, and perform better when faced with complex tasks.

Contests, team-building exercises, fitness programs, mental health breaks and other social activities, will make the work environment fun, interactive, and rewarding. Also playfighting, i.e. playful fights or fictive disputes, may contribute to organizations and institutions, as in youth care settings. Staff tries to down-key playfight invitations to “treatment” or “learning,” but playfighting also offers youth and staff identificatory respite from the institutional regime. Wästerfors (2016) has found that playfighting is a recurrent pattern in the social life of a youth care institution and sits at the core of what inmates and staff have to deal with

Seniors

Older adults represent one of the fastest growing populations around the world. In fact, the United Nations predicted an increase of those aged 60 and above from 629 million in 2002 to approximately two billion in 2050 but increased life expectancy does not necessarily translate to a better quality of life. For this reason, research has begun to investigate methods to maintain and/or improve quality of life among older adults. 

Similar to the data surrounding children and adults, play and activity are associated with improved health and quality of life among seniors. Additionally, play and activity tend to affect successful aging as well as boost well-being throughout the lifespan. Although children, adults, and seniors all tend to benefit from play, older adults often perform it in unique ways to account for possible issues, such as health restrictions, limited accessibility, and revised priorities. For this reason, elderly people may partake in physical exercise groups, interactive video games, and social forums specifically geared towards their needs and interests. One qualitative research study found older adults often chose to engage in specific games such as dominoes, checkers, and bingo for entertainment. Another study indicated a common pattern within game preferences among older adults; seniors often favor activities that encourage mental and physical fitness, incorporate past interests, have some level of competition, and foster a sense of belonging. Researchers investigating play in older adults are also interested in the benefits of technology and video games as therapeutic tools. Studies show these outlets can lower the risk of developing particular diseases, reduce feelings of social isolation and stress, as well as promote creativity and the maintenance of cognitive skills. As a result, play as been integrated into physiotherapy and occupational therapy interventions for seniors.

The ability to incorporate play into one's routine is important because these activities allow participants to express creativity, improve verbal and non-verbal intelligence as well as enhance balance. These benefits may be especially crucial to seniors because evidence shows cognitive and physical functioning declines with age. However, other research argues it might not be aging that is associated with the decline in cognitive and physical capabilities. More specifically, some studies indicate it could be the higher levels of inactivity within older adults that may have significant ramifications on their health and well-being.

With attention to these hypotheses, research shows play and activity tend to decline with age which may result in negative outcomes such as social isolation, depression, and mobility issues. American studies found that only 24% of seniors took part in regular physical activity and only 42% use the internet for entertainment purposes. In comparison to other age groups, the elderly are more likely to experience a variety of barriers, such as difficulty with environmental hazards and accessibility related issues, that may hinder their abilities to execute healthy play behaviours. Similarly, although playing may benefit seniors, it also has the potential to negatively impact their health. For example, those who play may be more susceptible to injury. Investigating these barriers may assist in the creation of useful interventions and/or the development of preventative measures, such as establishing safer recreational areas, that promote the maintenance of play behaviours throughout elderly life.

A significant amount of literature suggests a moderate level of play has numerous positive outcomes in the lives of senior citizens. In order to support and promote play within the older population, studies suggest institutions should set up more diverse equipment, improve conditions within recreational areas, and create more video games or online forums that appeal to the needs of seniors.

Animals

Cocker spaniel playing with a monkey doll

 

Evolutionary psychologists believe that there must be an important benefit of play, as there are so many reasons to avoid it. Animals are often injured during play, become distracted from predators, and expend valuable energy. In rare cases, play has even been observed between different species that are natural enemies such as a polar bear and a dog. Yet play seems to be a normal activity with animals who occupy the higher strata of their own hierarchy of needs. Animals on the lower strata, e.g. stressed and starving animals, generally do not play. However, in wild Assamese macaques physically active play is performed also during periods of low food availability and even if it is at the expense of growth, which strongly highlights the developmental and evolutionary importance of play.

The social cognitive complexity of numerous species, including dogs, have recently been explored in experimental studies. In one such study, conducted by Alexandra Horowitz of the University of California, the communication and attention-getting skills of dogs were investigated. In a natural setting, dyadic play behavior was observed; head-direction and posture was specifically noted. When one of the two dogs was facing away or otherwise preoccupied, attention-getting behaviors and signals (nudging, barking, growling, pawing, jumping, etc.) were used by the other dog to communicate the intent and/or desire to continue on with the dyadic play. Stronger or more frequent signaling was used if the attention of the other dog was not captured. These observations tell us that these dogs know how play behavior and signaling can be used to capture attention, communicate intent and desire, and manipulate one another. This characteristic and skill, called the "attention-getting skill" has generally only been seen in humans, but is now being researched and seen in many different species.

Observing play behavior in various species can tell us a lot about the player's environment (including the welfare of the animal), personal needs, social rank (if any), immediate relationships, and eligibility for mating. Play activity, often observed through action and signals, often serves as a tool for communication and expression. Through mimicry, chasing, biting, and touching, animals will often act out in ways so as to send messages to one another; whether it's an alert, initiation of play, or expressing intent. When play behavior was observed for a study in Tonkean macaques, it was discovered that play signals weren't always used to initiate play; rather, these signals were viewed primarily as methods of communication (sharing information and attention-getting).

A dog plays with a ball.

 

One theory – "play as preparation" – was inspired by the observation that play often mimics adult themes of survival. Predators such as lions and bears play by chasing, pouncing, pawing, wrestling, and biting, as they learn to stalk and kill prey. Prey animals such as deer and zebras play by running and leaping as they acquire speed and agility. Hoofed mammals also practice kicking their hind legs to learn to ward off attacks. Indeed, time spent in physical play accelerates motor skill acquisition in wild Assamese macaques. While mimicking adult behavior, attacking actions such as kicking and biting are not completely fulfilled, so playmates do not generally injure each other. In social animals, playing might also help to establish dominance rankings among the young to avoid conflicts as adults.

John Byers, a zoologist at the University of Idaho, discovered that the amount of time spent at play for many mammals (e.g. rats and cats) peaks around puberty, and then drops off. This corresponds to the development of the cerebellum, suggesting that play is not so much about practicing exact behaviors, as much as building general connections in the brain. Sergio Pellis and colleagues at the University of Lethbridge in Alberta, Canada, discovered that play may shape the brain in other ways, too. Young mammals have an overabundance of brain cells in their cerebrum (the outer areas of the brain – part of what distinguishes mammals). There is evidence that play helps the brain clean up this excess of cells, resulting in a more efficient cerebrum at maturity.

Humans and non-human animals playing in water

 

 

Playing in the surf is among the favorite activities of children at the beach

 

Dolphins playing in the surf

 

Marc Bekoff (a University of Colorado evolutionary biologist) proposes a "flexibility" hypothesis that attempts to incorporate these newer neurological findings. It argues that play helps animals learn to switch and improvise all behaviors more effectively, to be prepared for the unexpected. There may, however, be other ways to acquire even these benefits of play: the concept of equifinality. The idea is that the social benefits of play for many animals, for example, could instead be garnered by grooming. Patrick Bateson maintains that equifinality is exactly what play teaches. In accordance with the flexibility hypothesis, play may teach animals to avoid "false endpoints". In other words, they will harness the childlike tendency to keep playing with something that works "well enough", eventually allowing them to come up with something that might work better, if only in some situations. This also allows mammals to build up various skills that could come in handy in entirely novel situations. A study on two species of monkeys Presbytis entellus and Macaca mulatta that came into association with each other during food provisioning by pilgrims at the Ambagarh Forest Reserve, near Jaipur, India, shows the interspecific interaction that developed between the juveniles of the two species when opportunity presented itself.

Development and learning

Learning through play has been long recognized as a critical aspect of childhood and child development. Some of the earliest studies of play started in the 1890s with G. Stanley Hall, the father of the child study movement that sparked an interest in the developmental, mental and behavioral world of babies and children. Play also promotes healthy development of parent-child bonds, establishing social, emotional and cognitive developmental milestones that help them relate to others, manage stress, and learn resiliency.

Modern research in the field of affective neuroscience (the neural mechanisms of emotion) has uncovered important links between role play and neurogenesis in the brain. For example, researcher Roger Caillois used the word ilinx to describe the momentary disruption of perception that comes from forms of physical play that disorient the senses, especially balance.

Studies have found that play and coping to daily stressors to be positively correlated in children. By playing, children regulate their emotions and this is important for adaptive functioning because without regulation, emotions could be overwhelming and stressful. 

Evolutionary psychologists have begun to explore the phylogenetic relationship between higher intelligence in humans and its relationship to play, i.e., the relationship of play to the progress of whole evolutionary groups as opposed to the psychological implications of play to a specific individual.

Physical, mental and social

Various forms of play, whether it is physical or mental, have influenced cognitive abilities in individuals. As little as ten minutes of exercise (including physical play), can improve cognitive abilities. These researchers did a study and have developed an "exergame" which is a game that incorporates some physical movement but is by no means formal exercise. These games increase one's heart rate to the level of aerobics exercise and have proven to result in recognizable improvements in mental faculties In this study they use play in a way that incorporates physical activity that creates physical excursions. The results of the study had statistical significance. There were improvements in math by 3.4% and general improvements in recall memory by 4% among the participants of the study.

On the other hand, other research has focused on the cognitive effects of mentally stimulating play. Playing video games is one of the most common mediums of play for children and adults today. There has been mixed reviews on the effects of video games. Despite this, according to a research conducted by Hollis (2014), "[playing video games] was positively associated with skills strongly related to academic success, such as time management, attention, executive control, memory, and spatial abilities – when playing video game occurs in moderation".

Play can also influence one's social development and social interactions. Much of the research focuses on the influence play has on child social development. There are different forms of play that have been noted to influence child social development. One study conducted by (Sullivan, 2003) explores the influence of playing styles with mothers versus playing styles with fathers and how it influences child social development. This article explains that "integral to positive development is the child's social competence or, more precisely, the ability to regulate their own emotions and behaviors in the social contexts of early childhood to support the effective accomplishment of relevant developmental tasks.

Social benefits of play have been measured using basic interpersonal values such as getting along with peers. One of the social benefits that this researcher has uncovered is that play with parents has proven to reduce anxiety in children. Having play time with parents that involves socially acceptable behaviour makes it easier for children to relate to be more socially adjusted to peers at school or at play Social development involving child interaction with peers is thus an area of influence for playful interactions with parents and peers.

Play in educational practices

Anji play

Anji play is an educational method based on children's self-directed play in outside spaces, using simple tools made of natural material. The teachers and instructors only observe and document the children's independent play. The method was created by Cheng Xueqin and is organized in two hours of free play, when the children choose the available material they want to use and build structures to play.

While planning, experimenting, building and using the structures to play, the children have the opportunity to interact with peers, to think critically about what may work, to discuss the plan and organize the construction hard work. The process is observed and recorded by the teachers and instructors without intervention, even in instances of possible risk.

Before and after the two hours of play, the children have the opportunity to express their plans and discuss with the peers. After the play, they get the opportunity to draw, write or explain what they did. Then, they watch the videos recorded the same day and explain how they played and comment each other's creations.

Anji play is also called “true play” and its guiding principles are love, risk, joy, engagement and reflection. This method of self-initiated and self-directed play is applied at the pre-schools (to children from 3 to 6 years-old) in Anji county, East China.

Hox gene

From Wikipedia, the free encyclopedia

Hox genes, a subset of homeobox genes, are a group of related genes that specify regions of the body plan of an embryo along the head-tail axis of animals. Hox proteins encode and specify the characteristics of 'position', ensuring that the correct structures form in the correct places of the body. For example, Hox genes in insects specify which appendages form on a segment (e.g. legs, antennae, and wings in fruit flies), and Hox genes in vertebrates specify the types and shape of vertebrae that will form. In segmented animals, Hox proteins thus confer segmental or positional identity, but do not form the actual segments themselves. 

 

An analogy for the Hox genes can be made to the role of a play director that calls which scene the actors should carry out next. If the play director calls the scenes in the wrong order, the overall play will be presented in the wrong order. Similarly, mutations in the Hox genes can result in body parts and limbs in the wrong place along the body. Like a play director, the Hox genes do not act in the play or participate in limb formation themselves.

The protein product of each Hox gene is a transcription factor. Each Hox gene contains a well-conserved DNA sequence known as the homeobox, of which the term "Hox" was originally a contraction. However, in current usage the term Hox is no longer equivalent to homeobox, because Hox genes are not the only genes to possess a homeobox sequence: humans have over 200 homeobox genes of which 39 are Hox genes . Hox genes are thus a subset of the homeobox transcription factor genes. In many animals, the organization of the Hox genes in the chromosome is the same as the order of their expression along the anterior-posterior axis of the developing animal, and are thus said to display colinearity.

Biochemical Function

The products of Hox genes are Hox proteins. Hox proteins are a subset of transcription factors, which are proteins that are capable of binding to specific nucleotide sequences on DNA called enhancers through which they either activate or repress hundreds of other genes. The same Hox protein can act as a repressor at one gene and an activator at another. The ability of Hox proteins to bind DNA is conferred by a part of the protein referred to as the homeodomain. The homeodomain is a 60-amino-acid-long DNA-binding domain (encoded by its corresponding 180-base-pair DNA sequence, the homeobox). This amino acid sequence folds into a "helix-turn-helix" (i.e. homeodomain fold) motif that is stabilized by a third helix. The consensus polypeptide chain is:. Hox proteins often act in partnership with co-factors, such as PBC and Meis proteins encoded by very different types of homeobox gene.

Conservation

Expression of Hox genes in the body segments of different groups of arthropod. The Hox genes 7, 8, and 9 correspond in these groups but are shifted (by heterochrony) by up to three segments. Segments with maxillopeds have Hox gene 7. Fossil trilobites probably had three body regions, each with a unique combination of Hox genes.

 

Homeobox genes, and thus the homeodomain protein motif, are found in most eukaryotes. Hox genes, being a subset of homeobox genes, arose more recently in evolution within the animal kingdom or Metazoa. Within the animal kingdom, Hox genes are present across the Bilateria  (animals with a clear head-to-tail axis), and have also been found in Cnidaria such as sea anemones . This implies that Hox genes arose over 550 million years ago. In Bilateria, Hox genes are often arranged in gene clusters, although there are many exceptions where the genes have been separated by chromosomal rearrangements . Comparing homeodomain sequences between Hox proteins often reveals greater similarity between species than within a species; this observation led to the conclusion that Hox gene clusters evolved early in animal evolution from a single Hox gene via tandem duplication and subsequent divergence, and that a prototypic Hox gene cluster containing at least seven different Hox genes was present in the common ancestor of all bilaterian animals.

In most bilaterian animals, Hox genes are expressed in staggered domains along the head-to-tail axis of the embryo, suggesting that their role in specifying position is a shared, ancient feature. The functional conservation of Hox proteins can be demonstrated by the fact that a fly can function to a large degree with a chicken Hox protein in place of its own. So, despite having a last common ancestor that lived over 550 million years ago, the chicken and fly version of the same Hox gene are similar enough to target the same downstream genes in flies.

In Drosophila

Homeobox (Hox) gene expression in Drosophila melanogaster

 

Drosophila melanogaster is an important model for understanding body plan generation and evolution. The general principles of Hox gene function and logic elucidated in flies will apply to all bilaterian organisms, including humans. Drosophila, like all insects, has eight Hox genes. These are clustered into two complexes, both of which are located on chromosome 3. The Antennapedia complex (not to be confused with the Antp gene) consists of five genes: labial (lab), proboscipedia (pb), deformed (Dfd), sex combs reduced (Scr), and Antennapedia (Antp). The Bithorax complex, named after the Ultrabithorax gene, consists of the remaining three genes: Ultrabithorax (Ubx), abdominal-A (abd-A) and abdominal-B (abd-B).

Labial

The lab gene is the most anteriorly expressed gene. It is expressed in the head, primarily in the intercalary segment (an appendageless segment between the antenna and mandible), and also in the midgut. Loss of function of lab results in the failure of the Drosophila embryo to internalize the mouth and head structures that initially develop on the outside of its body (a process called head involution). Failure of head involution disrupts or deletes the salivary glands and pharynx. The lab gene was initially so named because it disrupted the labial appendage; however, the lab gene is not expressed in the labial segment, and the labial appendage phenotype is likely a result of the broad disorganization resulting from the failure of head involution.

Proboscipedia

The pb gene is responsible for the formation of the labial and maxillary palps. Some evidence shows pb interacts with Scr.

Deformed

The Dfd gene is responsible for the formation of the maxillary and mandibular segments in the larval head. The mutant phenotypes of Dfd are similar to those of labial. Loss of function of Dfd in the embryo results in a failure of head involution (see labial gene), with a loss of larval head structures. Mutations in the adult have either deletions of parts of the head or transformations of head to thoracic identity.

Sex combs reduced

The Scr gene is responsible for cephalic and thoracic development in Drosophila embryo and adult.

Antennapedia

The second thoracic segment, or T2, develops a pair of legs and a pair of wings. The Antp gene specifies this identity by promoting leg formation and allowing (but not directly activating) wing formation. A dominant Antp mutation, caused by a chromosomal inversion, causes Antp to be expressed in the antennal imaginal disc, so that, instead of forming an antenna, the disc makes a leg, resulting in a leg coming out of the fly's head. 

Wild type (left), Antennapedia mutant (right)

Ultrabithorax

The third thoracic segment, or T3, bears a pair of legs and a pair of halteres (highly reduced wings that function in balancing during flight). Ubx patterns T3 largely by repressing genes involved in wing formation. The wing blade is composed of two layers of cells that adhere tightly to one another, and are supplied with nutrient by several wing veins. One of the many genes that Ubx represses is blistered, which activates proteins involved in cell-cell adhesion, and spalt, which patterns the placement of wing veins. In Ubx loss-of-function mutants, Ubx no longer represses wing genes, and the halteres develop as a second pair of wings, resulting in the famous four-winged flies. When Ubx is misexpressed in the second thoracic segment, such as occurs in flies with the "Cbx" enhancer mutation, it represses wing genes, and the wings develop as halteres, resulting in a four-haltered fly.

Abdominal-A

In Drosophila, abd-A is expressed along most of the abdomen, from abdominal segments 1 (A1) to A8. Expression of abd-A is necessary to specify the identity of most of the abdominal segments. A major function of abd-A in insects is to repress limb formation. In abd-A loss-of-function mutants, abdominal segments A2 through A8 are transformed into an identity more like A1. When abd-A is ectopically expressed throughout the embryo, all segments anterior of A4 are transformed to an A4-like abdominal identity. The abd-A gene also affects the pattern of cuticle generation in the ectoderm, and pattern of muscle generation in the mesoderm.

Abdominal-B

Gene abd-B is transcribed in two different forms, a regulatory protein, and a morphogenic protein. Regulatory abd-B suppress embryonic ventral epidermal structures in the eighth and ninth segments of the Drosophila abdomen. Both the regulatory protein and the morphogenic protein are involved in the development of the tail segment.

Classification of Hox proteins

Proteins with a high degree of sequence similarity are also generally assumed to exhibit a high degree of functional similarity, i.e. Hox proteins with identical homeodomains are assumed to have identical DNA-binding properties (unless additional sequences are known to influence DNA-binding). To identify the set of proteins between two different species that are most likely to be most similar in function, classification schemes are used. For Hox proteins, three different classification schemes exist: phylogenetic inference based, synteny-based, and sequence similarity-based. The three classification schemes provide conflicting information for Hox proteins expressed in the middle of the body axis (Hox6-8 and Antp, Ubx and abd-A). A combined approach used phylogenetic inference-based information of the different species and plotted the protein sequence types onto the phylogenetic tree of the species. The approach identified the proteins that best represent ancestral forms (Hox7 and Antp) and the proteins that represent new, derived versions (or were lost in an ancestor and are now missing in numerous species).

Genes regulated by Hox proteins

Hox genes act at many levels within developmental gene hierarchies: at the "executive" level they regulate genes that in turn regulate large networks of other genes (like the gene pathway that forms an appendage). They also directly regulate what are called realisator genes or effector genes that act at the bottom of such hierarchies to ultimately form the tissues, structures, and organs of each segment. Segmentation involves such processes as morphogenesis (differentiation of precursor cells into their terminal specialized cells), the tight association of groups of cells with similar fates, the sculpting of structures and segment boundaries via programmed cell death, and the movement of cells from where they are first born to where they will ultimately function, so it is not surprising that the target genes of Hox genes promote cell division, cell adhesion, apoptosis, and cell migration.

Examples of targs

Organism	Target gene	Normal function of target gene	Regulated by
Drosophila	distal-less	activates gene pathway for limb formation	ULTRABITHORAX (represses distal-less)
	distal-less	activates gene pathway for limb formation	ABDOMINAL-A (represses distal-less)
	decapentaplegic	triggers cell shape changes in the gut that are required for normal visceral morphology	ULTRABITHORAX (activates decapentaplegic)
	reaper	Apoptosis: localized cell death creates the segmental boundary between the maxilla and mandible of the head	DEFORMED (activates reaper)
	decapentaplegic	prevents the above cell changes in more posterior positions	ABDOMINAL-B (represses decapentaplegic)
Mouse	EphA7	Cell adhesion: causes tight association of cells in distal limb that will form digit, carpal and tarsal bones	HOX-A13 (activates EphA7)
	Cdkn1a	Cell cycle: differentiation of myelomonocyte cells into monocytes (white blood cells), with cell cycle arrest	Hox-A10 (activates Cdkn1a)

Enhancer sequences bound by homeodomains

The DNA sequence bound by the homeodomain protein contains the nucleotide sequence TAAT, with the 5' terminal T being the most important for binding. This sequence is conserved in nearly all sites recognized by homeodomains, and probably distinguishes such locations as DNA binding sites. The base pairs following this initial sequence are used to distinguish between homeodomain proteins, all of which have similar recognition sites. For instance, the nucleotide following the TAAT sequence is recognized by the amino acid at position 9 of the homeodomain protein. In the maternal protein Bicoid, this position is occupied by lysine, which recognizes and binds to the nucleotide guanine. In Antennapedia, this position is occupied by glutamine, which recognizes and binds to adenine. If the lysine in Bicoid is replaced by glutamine, the resulting protein will recognize Antennapedia-binding enhancer sites.

However, all homeodomain-containing transcription factors bind essentially the same DNA sequence. The sequence bound by the homeodomain of a Hox protein is only six nucleotides long, and such a short sequence would be found at random many times throughout the genome, far more than the number of actual functional sites. Especially for Hox proteins, which produce such dramatic changes in morphology when misexpressed, this raises the question of how each transcription factor can produce such specific and different outcomes if they all bind the same sequence. One mechanism that introduces greater DNA sequence specificity to Hox proteins is to bind protein cofactors. Two such Hox cofactors are Extradenticle (Exd) and Homothorax (Hth). Exd and Hth bind to Hox proteins and appear to induce conformational changes in the Hox protein that increase its specificity.

Regulation of Hox genes

Just as Hox genes regulate realisator genes, they are in turn regulated themselves by other genes. In Drosophila and some insects (but not most animals), Hox genes are regulated by gap genes and pair-rule genes, which are in their turn regulated by maternally-supplied mRNA. This results in a transcription factor cascade: maternal factors activate gap or pair-rule genes; gap and pair-rule genes activate Hox genes; then, finally, Hox genes activate realisator genes that cause the segments in the developing embryo to differentiate. Regulation is achieved via protein concentration gradients, called morphogenic fields. For example, high concentrations of one maternal protein and low concentrations of others will turn on a specific set of gap or pair-rule genes. In flies, stripe 2 in the embryo is activated by the maternal proteins Bicoid and Hunchback, but repressed by the gap proteins Giant and Kruppel. Thus, stripe 2 will only form wherever there is Bicoid and Hunchback, but not where there is Giant and Kruppel.

MicroRNA strands located in Hox clusters have been shown to inhibit more anterior hox genes ("posterior prevalence phenomenon"), possibly to better fine tune its expression pattern.

Non-coding RNA (ncRNA) has been shown to be abundant in Hox clusters. In humans, 231 ncRNA may be present. One of these, HOTAIR, silences in trans (it is transcribed from the HOXC cluster and inhibits late HOXD genes) by binding to Polycomb-group proteins (PRC2).

The chromatin structure is essential for transcription but it also requires the cluster to loop out of the chromosome territory.

In higher animals including humans, retinoic acid regulates differential expression of Hox genes along the anteroposterior axis. Genes in the 3' ends of Hox clusters are induced by retinoic acid resulting in expression domains that extend more anteriorly in the body compared to 5' Hox genes that are not induced by retinoic acid resulting in expression domains that remain more posterior.

Quantitative PCR has shown several trends regarding colinearity: the system is in equilibrium and the total number of transcripts depends on the number of genes present according to a linear relationship.

Colinearity

In some organisms, especially vertebrates, the various Hox genes are situated very close to one another on the chromosome in groups or clusters. The order of the genes on the chromosome is the same as the expression of the genes in the developing embryo, with the first gene being expressed in the anterior end of the developing organism. The reason for this colinearity is not yet completely understood, but could be related to the activation of Hox genes in a temporal sequence by gradual unpacking of chromatin along a gene cluster. The diagram above shows the relationship between the genes and protein expression in flies.

Nomenclature

The Hox genes are named for the homeotic phenotypes that result when their function is disrupted, wherein one segment develops with the identity of another (e.g. legs where antennae should be). Hox genes in different phyla have been given different names, which has led to confusion about nomenclature. The complement of Hox genes in Drosophila is made up of two clusters, the Antennapedia complex and the Bithorax complex, which together were historically referred to as the HOM-C (for Homeotic Complex). Although historically HOM-C genes have referred to Drosophila homologues, while Hox genes referred to vertebrate homologues, this distinction is no longer made, and both HOM-C and Hox genes are called Hox genes.

In other species

Hox genes in various species

Vertebrates

The ancestors of vertebrates had a single Hox gene cluster, which was duplicated (twice) early in vertebrate evolution by whole genome duplications to give four Hox gene clusters: Hoxa, Hoxb, Hoxc and Hoxd. It is currently unclear whether these duplications occurred before or after divergence of lampreys and hagfish from the rest of vertebrates . Most mammals, amphibians, reptiles and birds have four HOX clusters, while most teleost fish, including zebrafish and medaka, have seven or eight Hox gene clusters because of an additional genome duplication which occurred in their evolutionary history . In zebrafish, one of the eight Hox gene clusters (a Hoxd cluster) has lost all protein-coding geens, and just a single microRNA gene marks the location of the original cluster.. In some teleost fish, such as salmon, an event more recent genome duplication occurred, doubling the seven or eight Hox gene clusters to give at least 13 clusters.

 

Hox genes, especially those of the HoxA and HoxD clusters, are implicated in the limb regeneration abilities of Amphibians and Reptiles.

Amphioxus

Amphioxus such as Branchiostoma floridae have a single Hox cluster with 15 genes, known as AmphiHox1 to AmphiHox15.

Other Invertebrates

Six Hox genes are dispersed in the genome of Caenorhabditis elegans, a roundworm. Hydra and Nematostella vectensis, both in the Phylum Cnidaria, have a few Hox/ParaHox-like homeobox genes. Hox gene expression has also been studied in brachiopods, annelids,  and a suite of molluscs.

History

The Hox genes are so named because mutations in them cause homeotic transformations. Homeotic transformations were first identified and studied by William Bateson in 1894, who coined the term "homeosis". After the rediscovery of Mendel's genetic principles, Bateson and others realized that some examples of homeosis in floral organs and animal skeletons could be attributed to variation in genes. 

Definitive evidence for a genetic basis of some homeotic transformations was obtained by isolating homeotic mutants. The first homeotic mutant was found by Calvin Bridges in Thomas Hunt Morgan's laboratory in 1915. This mutant shows a partial duplication of the thorax and was therefore named Bithorax (bx). It transforms the third thoracic segment (T3) toward the second (T2). Bithorax arose spontaneously in the laboratory and has been maintained continuously as a laboratory stock ever since.

The genetic studies by Morgan and others provided the foundation for the systematic analyses of Edward B. Lewis and Thomas Kaufman, which provided preliminary definitions of the many homeotic genes of the Bithorax and Antennapedia complexes, and also showed that the mutant phenotypes for most of these genes could be traced back to patterning defects in the embryonic body plan. 

Ed Lewis, Christiane Nüsslein-Volhard and Eric F. Wieschaus identified and classified 15 genes of key importance in determining the body plan and the formation of body segments of the fruit fly D. melanogaster in 1980. For their work, Lewis, Nüsslein-Volhard, and Wieschaus were awarded the Nobel Prize in Physiology or Medicine in 1995.

In 1983, the homeobox was discovered independently by researchers in two labs: Ernst Hafen, Michael Levine, and William McGinnis (in Walter Gehring's lab at the University of Basel, Switzerland) and Matthew P. Scott and Amy Weiner (in Thomas Kaufman's lab at Indiana University in Bloomington).

Future

Hox genes play critical roles in the development of structures such as limbs, lungs, the nervous system, and eyes. As T. R. Lappin and colleagues observed in 2006, "Evolutionary conservation provides unlimited scope for experimental investigation of the functional control of the Hox gene network which is providing important insights into human disease." In the future, more research can be done in investigating the roles of Hox genes in Leukaemia and cancer (such as EOC).

Designer drug

From Wikipedia, the free encyclopedia

A package of recreational drugs disguised in "bath salts" packaging.

 

A designer drug is a structural or functional analog of a controlled substance that has been designed to mimic the pharmacological effects of the original drug, while avoiding classification as illegal and/or detection in standard drug tests. Designer drugs include psychoactive substances that have been designated by the European Union as new psychoactive substances (NPS) as well as analogs of performance-enhancing drugs such as designer steroids. Some of these were originally synthesized by academic or industrial researchers in an effort to discover more potent derivatives with fewer side effects and were later co-opted for recreational use. Other designer drugs were prepared for the first time in clandestine laboratories. Because the efficacy and safety of these substances have not been thoroughly evaluated in animal and human trials, the use of some of these drugs may result in unexpected side effects.

The development of designer drugs may be considered a subfield of drug design. The exploration of modifications to known active drugs—such as their structural analogues, stereoisomers, and derivatives—yields drugs that may differ significantly in effects from their "parent" drug (e.g., showing increased potency, or decreased side effects). In some instances, designer drugs have similar effects to other known drugs, but have completely dissimilar chemical structures (e.g. JWH-018 vs THC). Despite being a very broad term, applicable to almost every synthetic drug, it is often used to connote synthetic recreational drugs, sometimes even those which have not been designed at all (e.g. LSD, the psychedelic side effects of which were discovered unintentionally). 

In some jurisdictions, drugs that are highly similar in structure to a prohibited drug are illegal to trade regardless of that drug's legal status. In other jurisdictions, their trade is a legal grey area, making them grey market goods. Some jurisdictions may have analogue laws which ban drugs similar in chemical structure to other prohibited drugs, while some designer drugs may be prohibited irrespective of the legal status of structurally similar drugs; in both cases, their trade may take place on the black market.

History

United States of America

1920s–1930s

Following the passage of the second International Opium Convention in 1925, which specifically banned morphine, the diacetyl ester of morphine, heroin, and a number of alternative esters of morphine quickly started to be manufactured and sold. The most notable of these were dibenzoylmorphine and acetylpropionylmorphine, which have virtually identical effects to heroin but were not covered by the Opium Convention. This then led the Health Committee of the League of Nations to pass several resolutions attempting to bring these new drugs under control, ultimately leading in 1930 to the first broad analogues provisions extending legal control to all esters of morphine, oxycodone, and hydromorphone. Another early example of what could loosely be termed designer drug use, was during the Prohibition era in the 1930s, when diethyl ether was sold and used as an alternative to illegal alcoholic beverages in a number of countries.

1960s–1970s

During the 1960s and 1970s, a number of new synthetic hallucinogens were introduced, with a notable example being the sale of highly potent tablets of DOM in San Francisco in 1967. There was little scope to prosecute people over drug analogues at this time, with new compounds instead being added to the controlled drug schedules one by one as they became a problem, but one significant court case from this period was in 1973, when Tim Scully and Nicholas Sand were prosecuted for making the acetyl amide of LSD, known as ALD-52. At this time ALD-52 was not a controlled drug, but they were convicted on the grounds that in order to make ALD-52, they would have had to be in possession of LSD, which was illegal. The late 1970s also saw the introduction of various analogues of phencyclidine (PCP) to the illicit market.

1980s–early 1990s

The modern use of the term designer drug was coined in the 1980s to refer to various synthetic opioid drugs, based mostly on the fentanyl molecule (such as α-methylfentanyl). The term gained widespread popularity when MDMA (ecstasy) experienced a popularity boom in the mid-1980s. When the term was coined in the 1980s, a wide range of narcotics were being sold as heroin on the black market. Many were based on fentanyl or meperidine. One, MPPP, was found in some cases to contain an impurity called MPTP, which caused brain damage that could result in a syndrome identical to full-blown Parkinson's disease, from only a single dose. Other problems were highly potent fentanyl analogues, which were sold as China White, that caused many accidental overdoses.

Because the government was powerless to prosecute people for these drugs until after they had been marketed successfully, laws were passed to give the DEA power to emergency schedule chemicals for a year, with an optional 6-month extension, while gathering evidence to justify permanent scheduling, as well as the analogue laws mentioned previously. Emergency-scheduling power was used for the first time for MDMA. In this case, the DEA scheduled MDMA as a Schedule I drug and retained this classification after review, even though their own judge ruled that MDMA should be classified Schedule III on the basis of its demonstrated uses in medicine. The emergency scheduling power has subsequently been used for a variety of other drugs including 2C-B, AMT, and BZP. In 2004, a piperazine drug, TFMPP, became the first drug that had been emergency-scheduled to be denied permanent scheduling and revert to legal status. 

The late 1980s and early 1990s also saw the re-emergence of methamphetamine in the United States as a widespread public health issue, leading to increasing controls on precursor chemicals in an attempt to cut down on domestic manufacture of the drug. This led to several alternative stimulant drugs emerging, the most notable ones being methcathinone and 4-methylaminorex, but, despite attracting enough attention from authorities to provoke legal scheduling of these compounds, their distribution was relatively limited in extent and methamphetamine continued to dominate the illicit synthetic stimulant market overall.

Late 1990s–2004

In the late 1990s and early 2000s, there was a huge explosion in designer drugs being sold over the internet. The term and concept of "research chemicals" was coined by some marketers of designer drugs (in particular, of psychedelic drugs in the tryptamine and phenethylamine family). The idea was that, by selling the chemicals as for "scientific research" rather than human consumption, the intent clause of the U.S. analogue drug laws would be avoided. Nonetheless, the DEA raided multiple suppliers, first JLF Primary Materials, and then multiple vendors (such as RAC Research) several years later in Operation Web Tryp. This process was accelerated greatly when vendors began advertising via search engines like Google by linking their sites to searches on key words such as chemical names and terms like psychedelic or hallucinogen. Widespread discussion of consumptive use and the sources for the chemicals in public forums also drew the attention of the media and authorities. 

In 2004, the US Drug Enforcement Administration raided and shut down several Internet-based research chemical vendors in an operation called Web Tryp. With help from the authorities in India and China, two chemical manufacturers were also closed. Many other internet-based vendors promptly stopped doing business, even though their products were still legal throughout much of the world. 

Most substances that were sold as "research chemicals" in this period of time are hallucinogens and bear a chemical resemblance to drugs such as psilocybin and mescaline. As with other hallucinogens, these substances are often taken for the purposes of facilitating spiritual processes, mental reflection or recreation. Some research chemicals on the market were not psychoactive, but can be used as precursors in the synthesis of other potentially psychoactive substances, for example, 2C-H, which could be used to make 2C-B and 2C-I among others. Extensive surveys of structural variations have been conducted by pharmaceutical corporations, universities and independent researchers over the last century, from which some of the presently available research chemicals derive. One particularly notable researcher is Dr. Alexander Shulgin, who presented syntheses and pharmacological explorations of hundreds of substances in the books TiHKAL and PiHKAL (co-authored with Ann Shulgin), and has served as an expert witness for the defense in several court cases against manufacturers of psychoactive drugs. 

The majority of chemical suppliers sold research chemicals in bulk form as powder, not as pills, as selling in pill form would invalidate the claims that they were being sold for non-consumptive research. Active dosages vary widely from substance to substance, ranging from micrograms to hundreds of milligrams, but while it is critical for the end user to weigh doses with a precision scale, instead of guessing ("eyeballing"), many users did not do this and this led to many emergency room visits and several deaths, which were a prominent factor leading to the emergency scheduling of several substances and eventually Operation Web Tryp. Some compounds such as 2C-B and 5-Meo-DiPT did eventually increase in popularity to the point that they were sold in pill form to reach a wider market, and acquired popular street names ("Nexus" and "Foxy," respectively). Once a chemical reaches this kind of popularity, it is usually just a matter of time before it is added to the list of scheduled (i.e., illegal) drugs.

The late 1990s and early 2000s also saw the first widespread use of novel anabolic steroids by athletes in competition. Steroids had been banned by the International Olympic Committee since 1976, but due to the large number of different anabolic agents available for human and veterinary use, the ability of laboratories to test for all available drugs had always lagged behind the ability of athletes to find new compounds to use. The introduction of increasingly formalised testing procedures, especially with the creation of the World Anti-Doping Agency in 1999, made it much more difficult for athletes to get away with using these drugs without detection, which then led to the synthesis of novel and potent anabolic steroid drugs such as tetrahydrogestrinone (THG), which were not detectable by the standard tests.

2005–2016

Popular designer drugs, 1990s-2016

 

While through recent history most designer drugs had been either opioids, hallucinogens, or anabolic steroids, the range of possible compounds is limited only by the scientific and patent literature, and recent years have been characterised by a broadening of the range of compounds sold as designer drugs. These have included a wide variety of designer stimulants such as geranamine, mephedrone, MDPV and desoxypipradrol, several designer sedatives such as methylmethaqualone and premazepam, and designer analogues of sildenafil (Viagra), which have been reported as active compounds in "herbal" aphrodisiac products. Designer cannabinoids are another recent development, with two compounds JWH-018 and (C8)-CP 47,497 initially found in December 2008 as active components of "herbal smoking blends" sold as legal alternatives to marijuana. Subsequently, a growing range of synthetic cannabinoid agonists have continued to appear, including by 2010, novel compounds such as RCS-4, RCS-8, and AB-001, which had never been reported in the literature, and appear to have been invented by designer drug manufacturers themselves. Another novel development is the use of research ligands for cosmetic rather than strictly recreational purposes, such as grey-market internet sales of the non-approved alpha-melanocyte-stimulating hormone tanning drugs known as melanotan peptides.

...what is new is the wide range of substances now being explored, the aggressive marketing of products that have been intentionally mislabelled, the growing use of the internet, and the speed at which the market reacts to control measures."

— EMCDDA director Wolfgang Goetz (November 2009).

Mephedrone and the cathinones marked somewhat of a turning point for designer drugs, turning them from little known, ineffective substances sold in head shops to powerful substances able to compete with classical drugs on the black market. Mephedrone especially experienced a somewhat meteoric rise in popularity in 2009 and the resulting media panic resulted in its prohibition in multiple countries. Following this there was a considerable emergence of other cathinones which attempted to mimic the effects of mephedrone, and with a newly attracted customer base, plenty of money to drive innovation.

Subsequently, the market rapidly expanded, with more and more substances being detected every year. In 2009, the EMCDDA's early warning system discovered 24 new drugs. In 2010, it found another 41; in 2011, another 49; and in 2012, there were 73 more. In 2013, a further 81 were identified: a total of 268 new drugs in just four years. These have not been limited to cathinones, with 35% being cannabinoids and the rest being composed of stimulants, benzodiazepines, psychedelics, dissociatives and to a lesser extent, every other class of drugs, even ibogoids and nootropics. As of 2017, the largest group of drugs being monitored by the EMCDDA is synthetic cannabinoids, with 169 different synthetic cannabinoids reported by December 2016.

Safety

The safety of research chemicals is untested and little if any research has been done on the toxicology or pharmacology of most of these drugs. Few, if any, human or animal studies have been done. Many research compounds have produced unexpected side-effects and adverse incidents due to the lack of screening for off-target effects prior to marketing; both bromo-dragonfly and mephedrone seem to be capable of producing pronounced vasoconstriction under some circumstances, which has resulted in several deaths, although the mechanism remains unclear. Substituted phenethylamines such as the 2C family and substituted amphetamines such as the DOx family have also caused a limited number of deaths.

Law

Due to the recent development of many designer drugs, laws banning or regulating their use have not been developed yet, and in recent cases novel drugs have appeared directly in response to legislative action, to replace a similar compound that had recently been banned. Many of the chemicals fall under the various drug analogue legislations in certain countries, but most countries have no general analogue act or equivalent legislation and so novel compounds may fall outside of the law after only minor structural modifications.

In the United States, the Controlled Substances Act was amended by the Controlled Substance Analogue Enforcement of 1986, which attempted to ban designer drugs pre-emptively by making it illegal to manufacture, sell, or possess chemicals that were substantially similar in chemistry and pharmacology to Schedule I or Schedule II drugs. 

Other countries have dealt with the issue differently. In some, the new drugs are banned as they become a concern, as in Germany, Canada, the United Kingdom, and Sweden. In Sweden, the police and customs from April 2011 may also seize drugs that are not on the list of drugs covered by the anti-drug laws if the police suspect that the purpose of the holding is related to drug abuse. Following a decision by a prosecutor, the police may destroy the seized drugs.

In Ireland, the Criminal Justice (Psychoactive Substances) Act 2010 bans substances based on their psychoactive effect, and was introduced as a catch-all to address the time lag between new substances appearing and their being banned individually. Draft legislation before the UK parliament as of July 2015 (the Psychoactive Substances Bill 2015-16) adopts a similar approach.

Some countries, such as Australia, have enacted generic bans but based on chemical structure rather than psychoactive effect: if a chemical fits a set of rules regarding substitutions and alterations of an already-banned drug, then it too is banned. Brazil adopted the same model as Australia, in a recent ruling from ANVISA, which is responsible to define what constitute drugs. 

Temporary class drug

A temporary class drug is a relatively new status for controlled drugs, which has been adopted in some jurisdictions, notably New Zealand and the United Kingdom, to attempt to bring newly synthesized designer drugs under legal control. The controlled drug legislation in these jurisdictions requires drug scheduling decisions to follow an evidence-based process, where the harms of the drug are assessed and reviewed so that an appropriate legal status can be assigned. Since many designer drugs sold in recent years have had little or no published research that could help inform such a decision, they have been widely sold as "legal highs", often for months, before sufficient evidence accumulates to justify placing them on the controlled drug schedules.

Common names

In the UK to avoid being controlled by the Medicines Act, designer drugs such as mephedrone have been described as "plant food," despite the compounds having no history of being used for these purposes.

In the USA, similar descriptions ("bath salts" is the most common) have been used to describe mephedrone as well as methylone and methylenedioxypyrovalerone (MDPV). Combined with labeling that they are "not for human consumption," these descriptions are an attempt to skirt the Federal Analog Act which forbids drugs that are “substantially similar” to already classified drugs from being sold for human use.

Synthetic cannabinoids are known under a variety of names including K2, Spice, Black Mamba, Bombay Blue, Genie, Zohai, Banana Cream Nuke, Krypton, and Lava Red. They are often called “synthetic marijuana,” “herbal incense,” or “herbal smoking blends” and often labeled “not for human consumption.”