CONTENTS 



PAGE 



PART I . INSTINCTIVE REACTIONS 1 



I . Introduction and Statement of the Problem 1 



II . Previous Experimental Work on Chicks 1 



III . General Apparatus 4 



IV . Observations and Experiments 5 



A. First Activities 5 



B. Drinking 8 



a. Problem 8 



b. Method and tests 8 



c. Discussion of results 11 



C. Pecking 14 



a. Apparatus and method 14 



b. Pecking artificially deferred 16 



c. The natural development of the pecking reaction, with 



a collateral study of the effects of social influence . 21 



1. Sources of error 21 



2. Data and their significance 26 



PART II . ACQUIRED REACTIONS 41 



I . Introduction and Statement of the Problem 41 



II . Apparatus 42 



III. Method 45 



IV . Experiments 48 



A. Color 48 



B. Form 53 



C. Size 57 



D. To What Extent Has Training General Value? 59 



E. Some Effects of Modifications 67 



F. The Persistence of Modifications 71 



Summary and Conclusions 75 



