72 WALTER S. HUNTER 



The constant maintenance of the cue under these conditions 

 of distraction and length of delay is highly improbable. Speak- 

 ing in conscious terms, it would require great concentration and 

 mental ability even for a human adult to keep any cue con- 

 stantly in "mind" during such conditions. (2) The cue might 

 be some intrinsically intermittent process such as an after- 

 image. Such substitutes, however, could not suffice to guide 

 reactions under the conditions of the experiment. Their pres- 

 ence at the moment of release would be purely accidental and 

 hence they can not account for the high percentage of correct 

 responses obtained. (3) We are forced to adopt the third hypo- 

 thesis that the cue disappears after being aroused by the light 

 stimulus, and is rearoused in some manner at the moment of 

 release. To explain the mechanism of this revival, we shall 

 assume that all three of the intra -organic cues have become 

 associated during the course of the experiment with some sen- 

 sory factor connected with the releasing of the animal. Hence 

 the release is a stimulus which tends to arouse all three intra- 

 organic tendencies. This revival, however, must be selective 

 and adaptive and this adaptiveness can be explained by two 

 additional assumptions. The presence of each light stimulus 

 at the beginning of delay excites its corresponding intra-organic 

 factor, and this excitement subsides after the disappearance of 

 the light. Although the release stimulus does tend to revive 

 all three factors, yet it will arouse that one most recently active, 

 viz., that excited by the light at the beginning of the delay. 

 The assumption that the predisposition of a tendency to response 

 depends upon its recency of functional activity is a recognized 

 principle of human psychology.'* With such a mechanism, it 

 would seem that the problem of delay should present no serious 

 difficulties. However, the time interval between tests, i.e., the 

 differences between the recency of excitation of the three fac- 

 tors, is small in many cases. Learning to enter the box most 

 recently lighted as opposed to the box most recently entered is 

 also no easy problem to master. 



As we have indicated, such a mechanism would apply only 

 to the non-orientation cues used by the raccoons and children. 

 The type of function here involved is ideational in character. 



^* Ladd and Woodworth. Elements of Physiological Psychology. New York, 

 1911, p. 285. 



