174 BEGINNINGS OF INTELLIGENCE 



ment, a discharge which finds its way to the same channels 

 as before, and so makes it likely that the same movement 

 will be repeated, the external conditions remaining the same. 

 Pleasure and pain can be agents of accommo- 

 dation and development only if the one pleasure, carry 

 with it the phenomenon of 'motor excess/ and the other, 

 pain, the reverse probably some form of inhibition or of 

 antagonistic contraction." 



The theories of Spencer, Bain and Baldwin are physio- 

 logical since they attempt to explain the modifications of 

 behavior, not through the influence of certain psychic states, 

 but as the effect of the physiological conditions of which these 

 states are the concomitants. The theories are all open to the 

 objection that pleasure is by no means the constant con- 

 comitant of heightened nervous discharge. Laughing and 

 crying are very similar in their physiological expression, 

 though they go along with very different psychic states, 

 A child who burns his hands and writhes about in agony 

 certainly manifests a heightened nervous discharge, but he 

 shows no tendency to put his hands again into the fire. 

 Another outreaching movement of the child brings his hands 

 toward a pleasant degree of warmth. The movement 

 tends to be repeated. The nervous discharge in the first 

 case is much greater than in the second, but in both cases 

 it goes to the arm, though along somewhat different nerves. 

 It is obvious, I think, that we cannot account for the differ- 

 ence between the responses to pleasurable and painful 

 stimuli on the basis of any quantitative difference in the 

 discharges to the part affected. It is a matter of nervous 

 connection rather than quantity of nervous energy. 



Pain-giving stimuli, owing to the arrangement of an animal's 

 reflex arcs, are generally followed by a withdrawing move- 

 ment of the part stimulated, but that there is a tendency 



