AN ANALYSIS OF THE LEARNING PROCESS IN THE SNAIL 37 



That the physiological state of the animal is in part responsible 

 for fluctuations in response is indicated by the no-response shown 

 in Tables II and III, pp. 8 and 13. Some of these were known 

 to be due to mechanical disturbance and are marked x in the 

 tables. Others were probably due to disturbance. Others again 

 may be attributed to the physiological state of fatigue, although 

 It is believed that the method of testing the snails alternately 

 practically eliminated this element. It is noteworthy that a 

 large percentage of the no-response trials occurs at the end of 

 the day's series. This may be attributed to fatigue or adapta- 

 tion — in either case a changed physiological state. 



With a more delicate apparatus, and particularly^ with the 

 elimination of external disturbances such as the vibrations 

 caused by sudden jars beyond the limits of the experimental 

 room, responses of more constant value might be obtained. It 

 is quite possible that responses obtained by more refined methods 

 would equal those of the salivar}^ reflex method in constancy. 



Throughout each of the tables it is to be noted that the duration 

 of the individual reaction is reasonably uniform. It fluctuates 

 mainly between 1.0 and 1.25 seconds. The fluctuations may be 

 attributed to the method of timing with a stop watch. Were 

 a better method available for the purpose, much greater uni- 

 formity in the reaction duration would doubtless appear. The 

 uniformity actually found is striking and indicates that the use 

 of the single reaction as a unit for measuring the response is 

 justified. The unit is probably as accurate as the drop of saliva. 



That the method described in this paper would yield results 

 if used in the study of discrimination in the snails the writer 

 does not doubt. It seems to oft'er for this purpose whatever 

 advantage the Pawlow method affords although possibly in a 

 less degree. It is also available in working out many of the 

 details of the association process in a statistical way. 



The data' presented in this paper show that the behavior of 

 the snail is modified by two processes, adaptation and learning. 



Adaptation appears throughout the experiments and needs 

 no extended discussion. It is enough to cite the following in- 

 stances. Others will doubtless appear from a study of the 

 tables. 



(a) The snails became " tame." When first brought into 

 the laborator}^ they expel the air from the lung and drop from 



