MAZE STUDIES WITH WHITE RAT 305 



The development of the act is contingent upon retinal impulses 

 in two ways. On the one hand, retinal impulses operate as 

 distractions, tending to prevent and delay the final perfection of 

 the coordination. This distractive effect is present even when 

 the relation of the visual environment to the rat remains stable. 

 Any alteration of the environment from trial to trial increases 

 the distractive effect. On the other hand, these retinal im- 

 pulses tend to promote or condition the organization of the 

 component elements of the act in so far as these impulses arouse 

 the motor activity requisite to the solution of the problem. 

 There are several w T ays of conceiving of this relation between 

 visual stimuli and increased learning capacity. The experiment 

 furnished no data for a choice between the several possibilities. 



The development of the act is also dependent upon olfactory 

 stimuli. No facts are pertinent as to the distractive or detri- 

 mental effect of these stimuli. Olfactory impulses, however, 

 aid in the development of the act. These stimuli may be uti- 

 lized as controls, or one may suppose that they are advantageous 

 because of their tonic effect upon the various activities involved 

 in the process of learning. No confident decision can be made 

 as between these alternatives, though the latter hypothesis re- 

 ceives the greater support from the relevant data. 



The act is still dependent upon these visual and olfactory 

 stimuli after it has become thoroughly automatized, provided it 

 was developed while these stimuli were present. The act can 

 be acquired and function successfully when these stimuli have 

 been completely eliminated. When the act was acquired whiie 

 these stimuli were present, it will still function successfully when 

 they are subtracted at least in part, or so long as their positional 

 relations to the organism remain unaltered. Any positional 

 change of these stimuli or the addition of new elements operate 

 to disrupt or interfere temporarily with the successful function- 

 ing of the act. These changes of the stimuli function as dis- 

 tractions; they release impulses which the organism is unable 

 to integrate successfully into the series of motor activities. The 

 act is temporarily disrupted or disorganized. 



Some degree of adaptation to these disturbances is the rule 

 for all sensory groups. The experiments furnished no data 

 which prove that smell is concerned in the process of adapta- 

 tion. Vision certainly possesses an adaptive function. Of the 



