VISUAL PERCEPTION OF THE CHICK 33 



The studies involving problem learning and ideation arose 

 merely as incidents in connection with the more fundamental 

 tasks. As the time of observing the chick's behavior in the 

 various problems lengthened, there was a proportional increase 

 of interest in the behavior itself. At last I gave in to a per- 

 sistent desire to record quantitatively the chick's characteristic 

 behavior in learning a particular task. From such an interest 

 it is a natural step to questions pertaining to evidences of 

 ideation in this learning. The problem of relative stimulus 

 difference, incidentally discussed in Chapter IX, represents an 

 initial approach to the study of the imaginal problem. 



Finally, another aspect of the problem, also arising quite 

 incidentally, was that of the relative value of the different visual 

 details. My earlier results with forms, largely negative, em- 

 phasized the desirability of considering the factors in combina- 

 tion as well as in isolation. In its normal life the chick is not 

 compelled to rely upon a single visual factor, but, on the con- 

 trary, it relies upon a natural combination of the visual details, 

 It thus seemed desirable to start with complex stimuli and from 

 this complex gradually to eliminate inequalities until a single 

 visual factor remained. This method might furnish data on 

 the relative value for the chick of the various visual factors. 



The plan adopted for solving these various problems was the 

 familiar Yerkes discrimination method. The description of the 

 apparatus sets forth the general features of the method. Condi- 

 tions both desirable and undesirable are presented to the chick. 

 Either nest box contains those things which the chick wants. 

 It provides food, light, warmth, and companionship. The ex- 

 periment box is arranged to make the chick seek escape. In the 

 entrance box the chick is closely confined; in both the entrance 

 and discrimination chambers the floors are wet; the entire re- 

 action box provides faint illumination, little warmth, no food, 

 and no companionship. The chick's problem is to learn how 

 to get from the undesirable to the desirable part of the appara- 

 tus. The two different stimuli are the signs by means of which 

 the chick may learn which way to escape. 



Each chick was taught the way of escape to the nest box by 

 means of 20 preliminary trials. The entrance to the nest box 

 at the side where the right stimulus appeared was open; the 

 sliding door closed the entrance from the electric box where the 



