Psychophysical Variations 31 



selection in evolution is often a psychophysical function or 

 character, it may be only the failure of psychophysical 

 observation which prevents the genetic explanation of a 

 series of organic changes. The search for utilities should 

 be extended to the mental sphere. The larger utility of 

 the psychological or the psychophysical may be the key- 

 note in a case of survival ; and the failure to discern this 

 utility may block our scientific progress. So it is, for 

 example, in appreciating many forms of play. If we 

 adopt the * practice ' theory, which holds that play is a 

 means of preparation, through preHminary practice, for 

 the strenuous specific activities of adult life, we must 

 recognize that it is often mental practice — in accommoda- 

 tion, judgment, social adaptability, etc., — or the training 

 of mental functions, which is the critical utihty ; and that 

 to understand this utility is at once to secure an appUca- 

 tion of natural selection, where otherwise, from the purely 

 organic point of view, no adequate ground of selection 

 would have been discoverable. 



While so much is true negatively, the matter has also a 

 positive aspect. The actual construction of a view regard- 

 ing a particular function or character can often be arrived 

 at only by weighing the psychological facts. So in the 

 case of the function just cited, animal play. There were 

 earlier theories of play. The ' surplus energy ' theory of 

 Spencer was generally held, despite the quite valid criticism 

 that it had the negative defect pointed out immediately 

 above : no adequate selective utility attaching to play was 

 involved so long as it was thought to be due to discharges 

 of surplus animal vigour only. The consequence was 

 that play — together with the whole province of art, 

 which is thought by many to have its roots in the play- 



