CHAPTER VI 



Form Perception 



The development of a definite procedure in the study of form 

 perception in the chick followed, in general, that which has been 

 described in the preceding chapter on size perception. A study 

 of the ability of the chick to discriminate between circles and 

 triangles which are equal in area was made with two of the 

 second group, chicks 9 and 11. The latter became afflicted 

 with "leg weakness" after the 24th series, up to which time it 

 had given no positive results. The results from chick 9 which 

 are presented in table 6 might be regarded as slightly positive. 



On the whole, the number of choices of the circle, as shown in 

 table 6, indicate some sort of discrimination. Series 10 was 

 perfect. Series 25 contains 9 correct choices and several series 

 reached 70 per cent or 80 per cent correctness. It is not sur- 

 prising that the chick became discouraged before a perfect habit 

 was established, for the plan of starting with complex stimuli 

 and working towards the single detail had not yet been adopted. 

 A system of control similar to that described in the preceding 

 chapter was followed throughout the work. The surprising 

 feature is the high percentage of "right" choices on January 4 

 and 5 when the chick was becoming discouraged and frightened. 

 This discouragement resulted in a rush for one stimulus or the 

 other as though "to get the choice over." It appears that there 

 was some sort of a difference between the two illuminations 

 which tended to attract the rushing chick, but this was not 

 clearly enough perceived for a dependable basis of response. 

 But even though a discrimination between the stimuli be ad- 

 mitted, it does not follow that the chick perceived form. As 

 has been pointed out in Chapter II, the distribution of light on, 

 or the unequal stimulation of, the different parts of the retina 

 may have been the discriminable basis. 



The result of this experience with chick 9 convinced me that 

 a better method was necessary to determine with certainty 

 whether the chick actually perceives form. When the study 



