Play is a term employed in ethology and psychology to describe to a range of voluntary, intrinsically motivated activities normally associated with pleasure and enjoyment.[1] Play is commonly associated with children, but positive psychology has stressed that play is imperative for all higher-functioning animals, even adult humans.

The rites of play are evident throughout nature and are perceived in people and animals, although generally only in those species possessing highly complex nervous systems such as mammals and birds.[2] Play is most frequently associated with the cognitive development and socialization of those engaged in developmental processes and the young. Play often entertains props, tools, animals, or toys in the context of learning and recreation. That is, some hypothesize that play is preparation of skills that will be used later. Others appeal to modern findings in neuroscience to argue that play is actually about training a general flexibility of mind – including highly adaptive practices like training multiple ways to do the same thing, or playing with an idea that is "good enough" in the hopes of maybe making it better.

Some play has clearly defined goals and when structured with rules is called a game, whereas, other play exhibits no such goals nor rules and is considered to be "unstructured" in the literature. Play promotes broaden and build behaviors as well as mental states of happiness – including flow.

Play has traditionally been given little attention by behavioral ecologists. Edward O. Wilson wrote in Sociobiology that "No behavior has proved more ill-defined, elusive, controversial and even unfashionable than play."[3] Though it received little attention in the early decades of ethology, and instead only existed as a matter of study within human psychology, there is now a considerable body of scientific literature resulting from research on the subject. Play does not have the central theoretical framework that exists in other areas of biology.

Ethologists frequently divide play into three general categories: Social play, locomotor play and object play. Locomotor play is the pretend playing that a very young animal participates in when alone.[4] The jumping and spinning characteristic of locomotor play can best be seen in young goats.[4] Researchers have theorized that locomotor play helps the cells in the cerebellum of the brain to develop connections.[4] Types of play listed by psychiatrist Dr. Stuart Brown expand upon these basic categories to include: fantasy and transformational play as well as body, object, social.[5] The National Institute for Play describes the previous five play types, as well as the play types attunement and narrative.[6]