TABLE OF CONTENTS 



Page 



Introduction 1 



I. Modifiability studied by a method analogous to the Pawlow salivary 



reflex method — learning through conditioned stimuli 1 



1. Outline of problem 1 



2. Material and methods in general 3 



3. Response to the food stimulus 5 



A. The response a reflex 5 



B. The number and duration of reactions in normal food 



stimulus response 7 



4. Response to the conditioned food stimulus, simultaneous food and 



pressure stimuli H 



A. Special apparatus and methods 12 



B. Experiments which show lack of response of untrained 



snails to pressure alone 12 



C. Experiments to determine response to the conditioned 



food stimulus, first food-pressure series 13 



D. Experiments with pressure alone on trained snails; asso- 



ciation i 24 



E. Experiments to determine the effect of training on the 



food-pressure response, second food-pressure series 27 



5. Summary of observations 31 



6. Discussion of modifiabihty through the method of simultaneous 



stimuli 3o 



II. Modifiability studied by the labyrinth method 39 



1. Introduction 39 



2. Apparatus and material 40 



3. Experiments on preference 42 



A. Experiments to test right-left preference 43 



B. Experiments to test preference for an ascending or des- 



cending path 46 



4. Experiments on learning the U-shaped labyrinth: choice of right 



and left paths; punishment; failure to get air 47 



5. Experiments with Y-shaped labyrinth; roughness as a warning 



signal ; electric-shock punishment 60 



6. Experiments with Y-shaped labyrinth; mechanical stimulus as 



warning signal; electric-shock punishment 72 



7. Summary of observations 81 



8. Discussion of learning by the labyrinth method 84 



III. Conclusions °' 



IV. Literature cited 88 



List of illustrations 89 



