ABSTRACT
The play of animals and children may be classified roughly in two main groups: play based on experimentation; and more or less organized play. Amongst the various suggestions that have been made at different times to explain the impulse to play, four are considered sufficiently important to be known as the “Play Theories.” These are: The Surplus Energy Theory; The Recreation Theory; The Practice Theory; and The Recapitulation Theory. Apart from the reported play of insects, play only seems to appear in the animal world when the species has reached a definite stage of development, when the nervous system has become differentiated into brain and spinal cord. The lengthening of the period of youth is always accompanied by an increase in the complexity of the play, which, both in the animal and the human being, seems to make use of a large number of tendencies necessary for adult life.
