AN ANALYSIS OF THE LEARNING PROCESS IN THE SNAIL 47 



TABLE IX 



Showing the tendency of six individuals of Physa gyrina Say to follow an 

 ascending or a descending path when the apparatus was tilted. The U-shaped 

 apparatus was used and the angle made by the cross bar of the U with a horizontal 

 measure. Both arms of the U reached the surface. 



58% 42% 42% 58% 52% 48% 58% 42% 72% 28% 



Table IX shows that when six individuals were given a choice 

 of an ascending or a descending path, both of which ended at 

 the surface, and when the angle of deviation from a horizontal 

 at the point of selection was not greater than 8 degrees, the 

 ascending path was chosen in 342 trials out of 600 or in 57% 

 of the trials. There appears to be a strong tendency to follow 

 the upward path only at the angle 7-8 degrees. In further 

 experiments the cross bar of the U was kept horizontal. 



4. Experiments on Learning the U-shaped Labyrinth; Choice of Right and 

 Left Path; Punishment Failure to Get Air 



Inasmuch as the snails showed a slight tendency to turn 

 toward the right in the preference tests, the right arm of the 

 U-shaped path was now shortened by cutting 2 cm. from the 

 upper end. A choice of this arm would lead to punishment 

 (failure to get air) and would be a wrong choice. When a wrong 

 choice was made the snail had to retrace its path to the point 

 of choice where it usually continued its course along the horizontal 

 bar and up the long arm to the surface of the water. This 

 was the only modification made in the apparatus for the learning 

 experiments. The method of handling the animals and the 

 apparatus was the same as in the preceding tests. Three snails 

 were used in these experiments. They were at first tested every 

 other day. The three snails were worked in turn and as many 

 trips given each as was possible in the time at the disposal of 



