266 ARTHUR C. WALTON 



and all showed 100% results, proving that the olfactory stimulus 

 was not necessarily a factoring one. During the 'same time, 

 check series were held to test the possible rhythm of the dog's 

 choice of compartments. A series of twenty-five trials was 

 given on No. 2 compartment, and one of ten trials on No. 1. 

 The first series gave 80% of the results correct, and the second 

 showed all the trials correct. These trials show that rhythm 

 was not a factor in the dog's choice and that the errors were 

 due to other causes. The habit of going to a different compart- 

 ment for each choice was so strong that it forced the dog at 

 first to another compartment in spite of the stimulus call ng 

 to the same compartment again. However, but five of the 

 thirty trials were mistaken in that way. That this rhythm 

 of going to one compartment did not form a habit was shown 

 by the fact that a return to the discrimination of the three 

 compartments showed no errors or even hesitations. These 

 results show that the dog can gain perfect mastery of a problem 

 involving the discrimination of three compartments when the 

 light stimulus is present at the time of reaction. The fact that 

 rhythmic and olfactory cues are not strong factors in successful 

 reactions is also shown. 



"B" — Condition "B" means the release box faced the food 

 compartments only for the stimulus, so that the dog could not 

 gain any possible cue from seeing the operators go to the com- 

 partment. Only trials of the "B2" type were given, the food 

 reward being given after the reaction was completed. Seventy- 

 one trials of this type were given preliminary to the undertaking 

 of the "Three Light" experiments in condition " B." Thirty- 

 nine, or 55 %, of the trials were correct reactions, and indicated 

 enough of mastery to favor the adoption cf the delay periods 

 of the " B " type. 



II. Delay Experiments, 



" Three Light Experiments." 



Condition "A" — Light out at release. This condition meant 

 that the light stimulus of five seconds' duration was present up 

 to the moment of the release. Thus the entire reaction. was 

 performed after the stimulus had been removed, but the associ- 

 ation was forced to bridge the gap between the instant of release 

 and the time of the choice of the compartment. As before, 



