EFFECT OF LENGTH OF BLIND ALLEYS ON MAZE LEARNING 45 



for the changes in behavior which gradually make response 

 more and more direct and which gradually eliminates the use- 

 less random acts. We must not forget that the numerous 

 internal life processes, e.g., the contractions of the muscles of 

 the stomach with hunger, serve as the motivation to activity. 

 They determine the stimulating value, as do also modifications 

 in the proprio-ceptive system by past behavior, of various 

 outside factors. The organism continues to respond by var\'- 

 ing behavior until successes are attained which modify these 

 internal conditions and change the inner motivating factors. 

 But the failures also change the organism. The directing fac- 

 tors of the response seem to be the inner organic processes 

 and the total combination of stimuli from external conditions 

 and from muscular contractions, all these overlapping in their 

 several effects as has been suggested. The neural channels 

 involved in the most consistent acts become the most opera- 

 tive through the compelling effects of all these factors, and 

 these acts, or directions of response, in time survive over all 

 others and gradually acquire an ease and automaticity of func- 

 tioning characteristic of habits. The stimuli to action even in 

 as simple an organism as a rat are infinitely more complex than 

 usually imagined in our " neural explanations." Mere contin- 

 gency in the combinations of acts of a rat brought about in 

 the maze, or in other problem boxes, for that matter, cannot 

 be regarded as the important factor that it has sometimes been 

 supposed to be. It is true that some useless acts may occa- 

 sionally survive with the more consistent ones by chance asso- 

 ciations, but such acts are really not vital parts of the s^'stem 

 of learned acts. 



The precise nature of the hold-over effects of various stimuli 

 posited in the explanations of learning here suggested must be 

 left to physiology and neurolog^^ There is undoubtedly a close 

 connection between sensor}- and motor impulses. Sensor^^ stim- 

 uli bring about responses which in their different stages of expres- 

 sion set up new afferent impulses, or either facilitate or tend to 

 inhibit old ones; these again modify the motor tendencies. We 

 are a long way yet from a satisfactory^ knowledge of nerve im- 

 pulses and their effects upon one another, — Are they periodic 

 or continuous? What relations obtain between stimulus changes 

 and nerve impulse changes"' What is the nature of inhibition 



