PLEASURE, PAIN AND THE BEGINNINGS OF 

 INTELLIGENCE 



S. J. HOLMES 



University of Wisconsin 



The tendency of animals to repeat acts which result in pleasure 

 and to discontinue or inhibit acts which bring them pain is a 

 fundamental feature of behavior on the utility of which it would 

 be superfluous to comment. But why do animals behave in this 

 fortunate manner, and how did they come to acquire the faculty 

 of so behaving? To our ordinary plain way of thinking it appears 

 sufficient to say that a dog eats meat because he likes it, and that 

 he runs away from the whip to avoid its painful incidence upon 

 his integument. These acts are such natural and obvious things 

 to do under the circumstances that to inquire why the animal does 

 what it likes and avoids what is disagreeable may seem a sort of 

 philosophic quibble which only a mind " debauched by learning" 

 would think of indulging in. But a little consideration will 

 show that we have here a real and very knotty problem, or rather 

 set of problems, of the greatest importance to the student of ge- 

 netic psychology. 



There are few better illustrations of the modification of behavior 

 through experiences of pleasure and pain than that afforded by 

 the behavior of young chicks, which has been so well studied by 

 Lloyd Morgan. A young chick when first hatched has the in- 

 stinct to peck at all sorts of objects of about a certain size. If an 

 object is a little too large the chick may hesitate. Should it 

 venture to peck at the object and derive a pleasant taste from it 

 the hesitation in the presence of similar objects becomes reduced 

 and will finally disappear. If the chick in the course of its peck- 

 ing seizes a caterpillar having a nauseous taste it is much less apt 

 to seize a similar caterpillar a second time. The painful or un- 



