1. If it was as much fun to study play as it is to
engage in it, more would be known about the
activity.
At this point little can be said about the
evolution of horse play or even how it differs
from play in other orders of mammals.
However a number of important studies of play
have been published which support the role of
play as an important factor in understanding the
evolutionary and adaptive behavior of some
species, including the horse. These studies
carried by
anthropologist, neurobiologist, evolutionist, bio
logist, ecologist, neurologist, psychologist and
other scientist allow us to gain some
understanding of play in intra and inter-specific
interactions.

2. Is play essential to development?
Is it the driving force behind human and animal behavior?
Some scholars have called play undefinable, nonexistent, or a mystery outside the realm
of scientific analysis.
Although playfulness may have been essential to the origin of much that we consider
distinctive in human and mammalian behavior, it only develops through a specific set of
interactions among developmental, evolutionary, ecological, and physiological
processes.
Play is the biological equivalent of a luxury item, the first thing to go when an animal or a
child is hungry or sick.
Furthermore, play is not always beneficial or adaptive.
For example 80% of deaths among juvenile seals occur because playing pups fail to spot
predator approaching. It is also extremely expensive in term of energy. Playful animals
use around 2 or 15 % of their energy cavorting. For evolutionary biologists even 2 or 15
% is huge - you just don’t find animals wasting energy like that, there must be a reason
for this dangerous activity. But if play is not simply a developmental hiccup, as biologists
once thought, why did it evolve?
One of the most popular explanations of play is that it helps juveniles develop the skills
they will need to hunt, mate and socialize as adults. Another is that it allows young
animals to get in shape for adult life by improving their respiratory endurance. Both
these ideas have been questioned in recent years.

3. One of the most popular explanations of play is that it helps juveniles develop the skills
they will need to hunt, mate and socialize as adults. Another is that it allows young
animals to get in shape for adult life by improving their respiratory endurance. Both
these ideas have been questioned in recent years.
Take the exercise theory. If play evolved to build muscle or as a kind of endurance
training, then you would expect to see permanent benefits. But Byers points out that the
benefits of increased exercise disappear rapidly after training stops, so any improvement
in endurance resulting from juvenile play would be lost by adulthood . "If the function of
play was to get into shape," says Byers, "I would expect the age distribution of play to
vary widely." The optimum time for playing would depend on when it was most
advantageous for the young of a particular species to get in shape. But it doesn't work
like that. Across species, play tends to peak about halfway through the suckling stage
and then decline to a low at weaning.
Then there's the skills-training hypothesis. At first glance, playing animals do appear to
be practicing the complex maneuvers they will need in adulthood. But a closer
inspection reveals this interpretation as too simplistic. In one study, behavioral ecologist
Tim Caro from the University of California looked at the predatory play of kittens and
their predatory behavior when they reached adulthood. He found that the way the cats
played had no significant effect on their hunting prowess in later life.

4. In another study, neuroscientist Sergio Pellis of the University of
Lethbridge in Alberta, Canada, scrutinized videos of rodents play fighting--
the most common form of social play in rodents. Despite superficial
similarities between this and the social, sexual and fighting behavior of
adult animals, Pellis's close examination of the play bouts revealed no
compelling link between play maneuvers and adult tactics. "For rats, and
probably other rodents," says Pellis, "the primary function of play fighting
does not appear to be to provide practice for either sex or aggression."

5. So what is going on, why play?
People have not paid enough attention to the amount of the brain activated by play says Marc
Bekoff from the University of Colorado. The idea is backed up by the work of neuropsychologist
Stephen Siviy of Gettysburg College in Pennsylvania. Siviy studied how bouts of play affect the
brain's levels of a protein called c-FOS--a substance associated with the stimulation and growth
of nerve cells. He was surprised by the extent of the activation. "Play just lights everything up,"
he says. He speculates that by allowing connections between brain areas that might not
normally be connected, play may be enhancing creativity.
All these findings paint a picture of how play might have originated. The comparative study
reported earlier this year by Pellis and his colleagues suggests a "stepwise" relationship between
increasing brain volume and the evolution of play. The researchers suggest that minor changes
in brain size might not have required evolutionary changes in play behavior, but at certain
threshold increases in volume, greater levels of playfulness evolved.

6. Behaving this way activates many different parts of the brain it is like a behavioral kaleidoscope,
with animals at play jumping rapidly from one activity to another. They use behavior from a lot
of different contexts--predation, aggression, reproduction their developing brain is getting all
sorts of stimulation.
Not only is more of the brain involved in play than was suspected, but it also seems to activate
higher cognitive processes. There's enormous cognitive involvement in play because play often
involves complex assessments of playmates, ideas of reciprocity and the use of specialized
signals and rules, play creates a brain that has greater behavioral flexibility and improved
potential for learning later in life. It's about more connectedness throughout the brain.
Play might be related to growth of the cerebellum, since they both peak at about the same time,
there is a sensitive period in brain growth during which time it’s important for an animal to get
the brain-growth stimulation of play to achieve its ultimate configuration, think of the relative
ease with which young children-but no infants or adults absorb language. This is a signature of a
‘’sensitive period’’ – a brief developmental window during which the brain can be modified in
ways that are not easily replicated earlier or later in life. In almost every species studied, a graph
of playfulness looked like an inverted ‘’U’’ increasing during the juvenile period and then falling
off around puberty, after which time most animal don’t play much anymore. In human the peak
period is between the ages of 1 to 4.

7. Play just light everything up by allowing connections between brain areas that might not
normally be connected, play may be enhancing creativity, and in other words, playing makes
you intelligent.
Prompted by the observation that play seems confined to the most intelligent animals, Byers
looked at the behavior and brain size of various marsupials. He found that playful species such
as the wombat have bigger brains for their body size compared with their lazier kin, which
include the docile koala. More recently, Pellis has teamed up with Andrew Iwaniuk of Monash
University in Melbourne to show that in primates, the amount the brain grows between birth
and maturity reflects the amount of play in which each species engages.
And earlier this year, Pellis, Iwaniuk and biologist John Nelson, also of Monash University,
reported that there is a strong positive link between brain size and playfulness for mammals in
general. It is the most extensive quantitative comparative study of juvenile play ever published.
Comparing measurements for 15 orders of mammals--from canids to dolphins, rodents to
marsupials--the team found larger brains (for a given body size) are linked to greater levels of
play. Likewise, animals with relatively small brains tend to play less.

8. Play has traditionally been classified into three basic categories:
- Object play, which involves the manipulation of inanimate things.
- Locomotors play, which consists of activities such as running and rotational body movements.
- Social play, which involves two or more individuals that respond to each other's actions.
(Fagen 1981)
There has been some movement in the literature to try to consider these types of play
separately because they develop at different times in ontogeny (Gomendio1988) and appear to
differ in their motivational basis (Pellis 1991). Furthermore, some of the explanations offered for
play pertain only to social play (e.g., social bonding, Carpenter 1934). This approach at first
seems very attractive because it subdivides an unwieldy research topic into smaller, seemingly
more manageable units. However, some descriptions of play suggest that object, locomotors
and social variants form a single natural category. First, different types of play tend to be
interspersed within the same play.

9. Lewis's recent findings point to the intriguing possibility that different types of play may have
evolved at different stages in evolutionary history, to allow the development of distinct regions
of the brain.
She looked at the relative size of the neocortex--which is responsible for social reasoning,
among other things--in primate species, and found that the larger the neocortex in each species,
the more social play they indulged in. But this relationship did not extend to object or motion-
based play. By implication, Lewis believes, social play may help wire up the social brain, while
other forms of play do not. "I think it's reasonably safe to assume that different types of play did
emerge at different points in time, but possibly with some overlap," she says.
The idea that play has evolved to build big brains certainly has its critics. Like much of behavioral
ecology, it rests on a scaffolding of correlations. "The problem with correlations is that they
don't consider unknown third variables," cautions Caro. "So maybe brain size and play are both
correlated with metabolic rate or some other factor? Certainly, something about being [warm-
blooded] seems important for promoting play."
Even some of the researchers whose results seem to support the link between brain building
and play are cautious in their assessment of the theory. Siviy believes there is not yet enough
evidence to settle the question. But he thinks the timing of play is convincing. "It's an ideal time
to do some learning, to make some modifications to brain circuitry," he says.
One of the strengths of the idea is its testability. Magnetic resonance imaging techniques that
identify myelin by-products, for example, should be able to show whether play boosts
myelination, as Lewis has suggested. What's more, measuring the volume and activity of certain
parts of the brain is becoming increasingly easy due to advances in non-invasive imaging.
If the theory is backed by experiment, what would it say about the way many of us in affluent
societies raise our children? We already know that rat pups denied the opportunity to play grow
smaller neocortices and lose the ability to apply social rules when they do interact with their
peers.

10. Discussions about play force us to reckon with our underlying ideas about childhood, sex
differences, creativity and success. Do boys play differently than girls? Are children being
damaged by staring at computer screens and video games? Are they missing something when
fantasy play is populated with characters from Hollywood’s imagination and not their own?
Most of these issues are too vast to be addressed by a single field of study. But the growing
science of play does have much to add to the conversation. Armed with research grounded in
evolutionary biology and experimental neuroscience, some scientists have shown themselves
eager — at times perhaps a little too eager — to promote a scientific argument for play. They
have spent the past few decades learning how and why play evolved in animals, generating
insights that can inform our understanding of its evolution in humans too. They are studying,
from an evolutionary perspective, to what extent play is a luxury that can be dispensed with
when there are too many other competing claims on the growing brain, and to what extent it is
central to how that brain grows in the first place.

11. Scientists who study play, in animals and humans alike, are developing a consensus view that
play is something more than a way for restless kids to work off steam; more than a way for
chubby kids to burn off calories; more than a frivolous luxury. Play, in their view, is a central part
of neurological growth and development — one important way that children build complex,
skilled, responsive, socially adept and cognitively flexible brains.
Their work still leaves some questions unanswered, including questions about play’s darker,
more ambiguous side: is there really an evolutionary or developmental need for dangerous
games, say, or for the meanness and hurt feelings that seem to attend so much child’s play?
Answering these and other questions could help us understand what might be lost if children
play less.

12. Fagen, R. 1981. Animal Play Behavior. New York: Oxford University Press.
Gomendio, M. 1988. The development of different types of play in gazelles:
implications for the nature and functions of play. Anim. Behav., 36,
825-36.
Pellis, S. M. 1991. How motivationally distinct is play? A preliminary case
study. Anim. Behav., 42, 851-3.
Carpenter, C. R. 1934. A field study of the behavior and social relations of
howling monkeys.
Animal Play by Marc Bekoff and John Byers, Cambridge University Press (1998)
"Do big-brained animals play more?" by Andrew Iwaniuk, John Nelson and Sergio Pellis, Journal
of Comparative Psychology, vol 115, p 29 (2001)
Tom Schierlitz The New York Times
The National Institute for Play Stuart Brown
The Genesis of Animal Play Gordon Burghardt