VISUAL PERCEPTION OF THE CHICK 9 



Eimer (8), Mills (22), and Morgan (23) also primarily Involves 

 the instincts. There Is a tendency for this transitional group to 

 become controversial over the problem of Instinct and acquisi- 

 tion. No definite experimental data are produced to settle the 

 disputed questions. Mills loosely reports some of his observa- 

 tions In diary form. The diary method also appears a few years 

 later in reports by Hunt (12) and Kline (19) in each of which 

 certain visual discriminative ability is described. 



Irritated by the controversies of this transition group and the 

 failure to answer on empirical grounds the disputed questions, 

 Thorndike (30) sets out on a procedure distinctively experi- 

 mental. However, he barely touches the problem of visual 

 acuity in the chick and, for the most part, his observations are 

 confined to crude studies of the chick's space and color per- 

 ceptions. 



Nearly ten years later, Hess (9-11) takes up the problem of 

 the chick's color vision as well as light and dark adaptation. 

 The method of Hess involves for the first time the use of the 

 dark room for studying visual acuity in the chick. Although 

 he greatly Improves on the method of Thorndike and deserves 

 praise for introducing the controllable method of the dark room 

 which has later been highly refined, Hess nevertheless often 

 leaves the reader uncertain of the experimental conditions. 

 He should be credited with ingenuity and alertness, but his 

 method in certain details is too crude for the problems with 

 which he deals. 



A study, certainly deserving more severe criticism than the 

 work of Hess, has been jointly reported by Katz and Revesz 

 (18). These authors have hastily considered a variety of 

 topics relative to the chick's visual discriminative ability. 

 Their crude "Klebmethode" has been applied to several phases 

 of the problem, including the topics of size and form perception 

 as well as color discrimination in "unsuppressed daylight." 



In its simpler form, the "Klebmethode" of Katz and Revesz 

 consists In pasting on a cardboard kernels of grain at which the 

 chick's pecking response Is to become Inhibited. Among these 

 "glued" kernels is scattered a different kind of grain which the 

 bird Is allowed to pick up. To Illustrate, It was found by the 

 experimenters that the chicks preferred rice to wheat. The 

 bird was classed as "Fehlerfrei" when It bad picked up the loose 



