214 THE PLAY OF ANIMALS. 



The principal difference is that the motions of the 

 human dancer less clearly betray the courting instinct, 

 though it is none the less there, however latent, and we 

 may learn much from the courtship of birds that is ap- 

 plicable to man as well. 



8. Curiosity. 



Curiosity is the only purely intellectual form of 

 playfulness that I have encountered in the animal 

 world. It is apparently a special form of experimen- 

 tation, and its psychologic accompaniment is attention, 

 which indeed is a requisite to the exercise of most of 

 the important instincts. Leroy has said that three 

 things demand the animal's attention: the cravings of 

 hunger, those of desire, and the necessity of avoiding 

 danger,* and Eibot, too, assigns the same reasons for 

 its importance.! This important faculty finds a play- 

 ful expression in curiosity, which may be called sportive 

 apperception. This function, that forms an essential 

 element in the activity of all the principal instincts, 

 especially those of feeding and flight, oversteps its utili- 

 tarian character in curiosity and becomes play. The 

 necessity for mental exercise is the primary reason for 

 this kind of playfulness, added to the increase of knowl- 

 edge. As James expresses it, it aids in the preservation 

 of the species, " inasmuch as the new object may al- 

 ways be advantageous." J 



* Lettres philosophique sur Pintelligence et la perfectibilite des 

 animaux, p. 71. 



f Th. Ribot, Psychologie de l'attention, p. 44. I think Ribot is 

 right in emphasizing hunger and fear more than desire. 



X W. James, Principles of Psychology, ii, p. 429. I have already 

 pointed out that all play employs the attention, and, indeed, all 

 the mental powers. Sikorski shows that attention is developed in 



