DELAYED REACTION 79 



itself is valid. Future work must attempt the formulation of 

 the functional differences between them. 



The result of the above theoretical considerations is a 

 classification of the grades of animal learning different from 

 those hitherto advanced. Washburn," e.g., has presented 

 three classes: "First, there is the condition where, so far as 

 we can see, the animal does not learn by individual experience. 

 * * * In the next place, ve have the grade where the ani- 

 mal learns by experience, without having the power to recall 

 an image of its experience. * * * Finally, * * * ^ye 

 have the possibility of an image." I would modify this scheme 

 by the insertion of a stage called sensory thought between the 

 second and third stages. The table would then read: (i) The 

 animal shows an absence of learning by experience. (2) The 

 animal is able to profit by experience, but has no higher capacity 

 than "trial and error" or the "stimulus and response" behavior 

 would indicate. The rats and dogs of the present tests come 

 here. (3) The animal can learn by the "trial and error" method. 

 Indeed, probably most of its reactions are on this basis, being 

 ruled by stimulus and response. But a new element now makes 

 its appearance, viz., sensory thought, which is a representative 

 function of strictly sensory content. The raccoons that I used 

 are in this class. Of the children, F is the most likely to belong 

 to this class. (4) The fourth grade reveals .the presence both 

 of "stimulus and response" behavior and of sensory thought, 

 but added to these is the possibility of directing reactions by 

 images. The older children of the present tests very probably 

 belong here rather than in the third class. 



VII. SUMMARY AND CONCLUSIONS 

 The following is a statement of the results and conclusions 

 that have been reached as a result of the foregoing experiments 

 and analyses: 



I. The rats (one excepted), dogs, raccoons and children made 

 successful reactions in situations where the customary deter- 

 mining stimulus was absent at the moment of response. The 

 stimulus might appear in an}' one of three boxes. These boxes 

 were qualitatively alike, but situated in dift'erent directions 



^ Op. cit., p. 276. 



