The purpose of this study by Britt and Janus is '(a) to examine the theoretical considerations of play, (b) to evaluate some representative empirical studies, and (c) to suggest some problems for further investigation'. There is no attempt by the authors to present a rigid definition of play, 'instead, they have included representative studies of what various investigators have called play, and have made no sharp distinction between play, games and amusements'.

Five theoretical considerations of play were found:

• 1The biological, which considers play the result of 'surplus energy' or 'the resulting activity of unused muscles', but omits any explanation of the form taken by play or of where surplus energy arises.

• 2The psychobiological, which seeks the real essence of play in instincts