play takes different forms in different animals , including humans , and its content provides some hint as to what purpose it might serve .
play researchers ( there s a fun - sounding job ) recognize three major types of play .
most common is object play ; that s what pigface does with basketballs and hoops .
object play is typically found in species that hunt , scavenge , or eat a wide variety of foods . about as common
( the term locomotor has to do with coordinated movement , such as crawling , walking , or running . )
locomotor play is common among animals that move around a lot  for instance , those that swim , fly , or live in trees  and , notably , often must get away from predators .
social play can take many forms , including mock fighting , chasing , and wrestling .
social play is especially prominent in animals that show a lot of behavioral flexibility or plasticity . in mammals and birds ,
this boils down to a simple rule : if your species has a big brain for its body size , you probably engage in social play.3 among these species , most of the variation in brain size occurs in the forebrain ; different mammals or birds of a given body size will have about the same amount of brain stem but very different amounts of neocortex ( in mammals ) or forebrain ( in birds ) . animals with more neocortex or forebrain typically live in larger groups and have more complex social relations .
ducks engage in so - called coordinated loafing , which means they basically just hang around together .
great apes and their relatives ( such as humans ) form societies in which alliances constantly shift , and in which the young play recognizable games , such as chasing , wrestling , and tickling . in playing these games , your child is indulging her inner ape .
this phenomenon is not limited to vertebrates . among invertebrates , cephalopods , which include squid and octopuses , have perhaps the most complex brains .
octopuses use their water jets to push floating objects like pill bottles back and forth in a tank or in a circular path.4 despite this behavioral complexity , however , octopus brains are still small by vertebrate standards  half the diameter of a dime , smaller than those of even the smallest mammals .
another invertebrate that appears to play is the honeybee , which has one of the largest and most complex nervous systems among invertebrates . as a counterexample , playlike behavior
now , maybe play is nt  for  anything . perhaps play behavior is simply early maturation  precocious behavior that develops before it is absolutely required .
another possibility is that play is what our brains do when there are no more pressing matters  a screensaver for the mind , as it were .
but one key piece of evidence contradicts these ideas : play is fun . at first , this may seem like an odd argument . are nt fun activities the ones we engage in for their own sakes ?
for example , we may think we seek sex because it s fun , but in reality , sex is essential .
people who do nt like sex have a harder time finding mates and having kids . in general , enjoying an activity is a hardwired response that causes the brain to seek out that activity . if these essential behaviors were nt enjoyable , we might forget to do them . on these grounds
, it seems that play must have an adaptive purpose , providing some survival advantage .
the brain generates chemical signals that encode a key component of fun : reward , the quality that makes us come back for more .
reward is conveyed within the brain by dopamine , a neurotransmitter that has many functions depending on where and when it is secreted .
dopamine is made by cells in the brain s core , in the substantia nigra and the ventral tegmental area ( see figure ) . in rats , dopamine and play
are linked . among chemicals that activate receptors for various neurotransmitters , including drugs that activate dopamine receptors , only a few increase play behavior.5 one way to find out
what play is good for is to take it away from animals and see how they fare .
animals ( including children ) are irrepressible ; they play under the most adverse of conditions .
the only way to get an animal to stop playing is to restrain its mobility .
this severe restriction leads to decreases in physical activity and increases in stress , as measured by the amount of the stress hormone cortisol in saliva .
play , exercise , and stress are closely linked . though the deprivation experiment is hard to do , that very fact means that seeing an animal play already tells us something good about its state . in young squirrel monkeys , low levels of cortisol
are associated with high amounts of play , suggesting either that play reduces stress or , possibly , that unstressed monkeys are more likely to play . in bear cubs during their first year of life , survival over the winter is highly correlated to the amount that cubs played during the preceding summer .
no matter how you slice it , seeing your child play is a good sign .
play activates other brain signaling systems as well , including the neurotransmitter norepinephrine ( see figure ) .
its close relative epinephrine ( also known as adrenaline ) is released to the body as an initial component of stress - related signaling .
as the main activator of the sympathetic nervous system , epinephrine mobilizes our energies for  fight , flight , fright , or fornication ,  as the medical - school mnemonic goes .
norepinephrine is also involved in rousing us to attention and action , but by acting as a neurotransmitter .
, norepinephrine improves brain plasticity , such that change becomes possible when this chemical is present in elevated amounts .
the same is true for dopamine , which accounts for how reward leads to long - term changes to make us want more  neural plasticity mechanisms are strongly facilitated when reward occurs .
though real - life stressors trigger the release of both epinephrine and cortisol , play does not increase cortisol .
cortisol is a stress hormone that helps us in genuinely dangerous situations by redirecting resources to the most urgent needs , such as repairing a wound or fighting an infection . in the case of the brain,6 enhancing memories of danger and learning about the stressful context
at hand are urgent ; other brain mechanisms , such as working memory and recall of social memories and of other facts and events , are not urgent .
it is safe to say that if you find play to be a source of stress , you re not doing it right . even violent video games , which raise physiological arousal as measured by epinephrine - based response , do not increase cortisol.7 in some cases , cortisol levels actually decrease  people work off stress by shooting em up . on the whole ,
the conditions of play  the generation of signals that enhance learning without an accompanying stress response  allow the brain to explore possibilities and to learn from them . thus , a major function of play may well be to provide practice for real life .
evidence from animals suggests that this is the case for play , which usually reflects an animal s more serious needs .
kittens play at pouncing on objects , a behavior that resembles the hunting they do later .
fawns do nt pounce much , but they do gambol around , a behavior that resembles escape .
so it s possible that play is practice that prepares animals for the real activity later  when it matters .
researchers of early childhood development have applied the concept of play skill building in tools of the mind , a preschool program that uses complex play to get children to make elaborate plans and to exercise self - restraint  practice for the prefrontal cortex , which is involved in self - control . even before that , the 19th - century kindergarten movement , which popularized the concept of preschool education , was based on the idea that songs , games , and other activities are a means for children to gain perceptual , cognitive , social , and emotional knowledge that prepares them for entering the world . in mammals ,
rats and cats raised in social isolation become incompetent in dealing with others of their kind and typically react with aggression . in our species ,
serial killers are often reported to have had abnormal play habits , keeping to themselves or engaging in particularly cruel forms of play .
play also transmits culture.8 middle - class mothers in the united states encourage their infants to pay attention to objects and are likely to prompt them to play with toys such as blocks .
japanese mothers encourage their babies to engage in social interactions while playing  for example , suggesting that they feed or bow to their dolls .
communities that emphasize the development of independence place more importance on object play , while interdependent communities encourage social play .
for one thing , though play by definition occurs in the absence of stressors or external threats , children are nt always good at detecting threats , such as the hazards of fast - moving traffic ; thus , play can be dangerous .
, 22 of 26 deaths happened when the pups played outside the sight or hearing of their parents .
it tests boundaries and establishes what is safe and what is dangerous . in the united states ,
playground equipment has been made very safe , leading to the unanticipated problem that children lack experience with such distinctions , which may lead to trouble later in life .
in addition to providing experience , play also helps children learn what they like and do nt like .
nobel chemistry laureate roger tsien tells of reading about chemical reactions before he was eight years old and then trying out the reactions for himself .
because he did nt have enough laboratory glassware , he had to make equipment from used milk jugs and empty hawaiian punch cans ( see photo ) .
tsien later won the nobel prize for developing colored dyes and proteins that become brighter or change hue when they encounter chemical signals in living cells , including neurons .
( this can make certain biological processes , such as brain signaling , much easier to see and to understand . )
tsien s great contribution to science  the invention of tools that help us visualize what is happening in active biological systems  had its roots in his childhood interest in home chemistry experiments .
not all childhood endeavors lead to such heights , of course , but regardless of your children s eventual interests , discovering them may be one of the most important outcomes of play . a homemade chemistry apparatus built by nobel laureate roger tsien when he was about 14 years old .
conversely , work in adult life is often most effective when it resembles play . indeed ,
total immersion in an activity often indicates that the activity is intensely enjoyable ; this is the concept of flow , or what athletes call being in the zone .
flow occurs during active experiences that require concentration but are also highly practiced , where the goals and boundaries are clear but leave room for creativity .
this describes many adult hobbies , from skiing to music , as well as careers like surgery and computer programming .
such immersion can make solving a great challenge as easy as child s play . encouraging your child to pursue tasks that produce flow is a great way to contribute to his lifelong happiness
it is perhaps the most effective way for them to learn life skills and to find out what they like . for these reasons ,
it is important to prevent play from becoming a compulsory , dreary activity , as its enjoyable nature is part of what makes most children grow like dandelions .
so , rather than trying to change your child s personality through enforced activities , let her play , and help her become who she s going to be .
 editor s note : an extraordinary number of species  from squid to lizards to humans  engage in play . 
 but why ? 
 in this article , adapted from dr . 
 sam wang and dr . 
 sandra aamodt s book welcome to your child s brain : how the mind grows from conception to college ( bloomsbury usa , 2011 ; oneworld publications , 2011 ) , the authors explore how play enhances brain development in children . as wang and aamodt describe , play activates the brain s reward circuitry but not negative stress responses , which can facilitate attention and action . through play , 
 children practice social interaction and build skills and interests to draw upon in the years to come . 
Types of Play
Play: What Is It Good For?
Stress Systems
Play as Practice
When Play Becomes Passion