Play defines human childhood
The human post-natal stages of infant, child and juvenile may be defined by many biological, socio-cultural, and cognitive characteristics. In addition, styles of play behavior differ between stages. Developmental psychologists and human ethologists describe many types of human play, including pretend play, games of chance and skill, and language play. Another type is physical activity play, the type of play shared by all social mammals. Well-known examples of this type of play are seen in the behavior of dogs, cats, lions, and most monkeys and apes. These animals begin to show physical-activity play via interactions with their mother —playing with her tail, and feet, or jumping on her body. By late infancy, the young are playing with each other in games of chasing and dominance. The intensity of this play increases during the juvenile years, when the young are more independent but not sexually mature. As the juveniles become sexually mature their interest turns from play to adult activities.
In contrast, age trends in human physical activity play are more complex than in other social mammals. Part of the reason for this is the addition of the childhood stage of human development. The human pattern begins with «Rhythmic stereotype» play. An example is when an infant, lying in a crib, repeatedly swats at a mobile suspended above its head. Body rocking and foot kicking are other examples of rhythmic stereotypes. The next type of physical activity play is called «Exercise play». It begins during late infancy and its frequency increases during the childhood years of life. This type of play involves vigorous movement, such as running and jumping, and the manipulation of moveable objects, such as balls and blocks. The third physical play type, «Rough and tumble» play, becomes common during late childhood and the juvenile stage. This type of play involves physical contact with other players, for example wrestling, gymnastic-like movements, and competitive games. Human play researchers report that the frequency of all types of play, but especially physical activity play, peaks between the ages of 4 to 5 years, that is, during the biologically defined childhood stage of life. The frequency of physical activity play during childhood work to promote healthy brain development. The human brain undergoes wondrous growth and transformations during the first 6 years of postnatal life. The brain is nearly adult size by age 7 years, which is the end of the Childhood stage. In the modem world, with physical limitations from intense urbanization and its attendant risks (e.g., crime, motorized traffic, loss of open spaces) there are often fewer opportunities for physical play, and this imposes a risk for the healthy growth and development of young people. [Barry Bogin]