iv MENTAL DEVELOPMENT 55 



modification of impulse by impulse, of a by /8. The pre- 

 cise function of consciousness then in sensori-motor action 

 is to grasp the unique combination of stimuli, each of which 

 having its special reaction modified by the concomitant 

 reactions, there follows a response appropriate to the unique 

 situation as a whole. 



In man all skill is acquired, and few, if any, sensori- 

 motor adjustments are wholly innate. But among the 

 lower animals the hereditary mechanism plays a larger 

 part. The pecking of a chick, the spinning of a spider's 

 web, are highly developed (though not perfect) from birth, 

 and there is no reason to deny that such adjustments might 

 be fully perfected by heredity. But in any such case one 

 of two things would seem to hold. Either the adjustment 

 must be such that every variation in the position or move- 

 ment of the object to be dealt with can call out a response 

 which will be suitable in the great majority of cases a type 

 response. In that event a preformed machinery can deal 

 with the situation. Or if that is impossible, if, say, the 

 possible movements of a prey are so individual and uncer- 

 tain that no two situations will be alike, then we must 

 infer a function capable of dealing with the novel and the 

 individual. That will be a function identical in its opera- 

 tion with the conscious attention to the object which we 

 have noted in the parallel case among ourselves. There 

 is no difficulty in supposing this function to operate on 

 the basis of a hereditary structure just as it operates on a 

 structure which is modified and improved by practice. To 

 crouch and spring are hereditary modes of action. Just 

 how long to crouch, and when and how to spring will be 

 determined by the keen-eyed watching of the behaviour of 

 this particular prey. Much of the more complex activity 

 of the lower animals may be and probably is of this type. 

 That is, it is sensori-motor action where a hereditary struc- 

 ture is guided in its response by a sense- synthesis of the 

 objects with which it has to deal. 



In either case, whether it is operating upon an inherited 

 or an acquired structure, how consciousness effects the 

 suitable response is unknown. All that we can say about 

 it is negative. Though it is consciousness its method is 



