INSTINCTS AND HABITS IN CHICKS 59 



of the large opening would be brighter than that back of the 

 small one. The angle at which the cards stood to each other, 

 together with the position of the windows with reference to the 

 cards, made it possible to vary the brightness of the two cards 

 independently, and that of the electric boxes so that the electric 

 box on the side of the brighter card could be made also the 

 brighter box. A cardboard over an electric box was also used 

 to screen off light. Within the degrees of variation employed, 

 the chicks continued to select the smaller opening regardless 

 of the relative brightness of the faces of the cards or the electric 

 boxes. When both electric chambers were covered with a ground 

 glass plate and a 2 c.p. electric light was adjusted over the 

 electric box on the side of the small opening, no. 24 approached 

 as usual the small opening, hesitated a moment, glanced about 

 the apparatus in the vicinity of the card, and then slowly en- 

 tered. (See control test 3, table 19.) Control 5 exhibits the 

 same general relations as 3, but without the use of electric light. 

 The pronounced variation, even to a different quality of light, 

 did not inhibit the selective reaction. In control series 4 the 

 electric box on the side of the card having the large opening 

 was darkened considerably by cutting off' the light from above 

 with a piece of black cardboard. The figures for this series of 

 reactions, lo-o, in comparison with the 9-1 records in the other 

 series, represent but do not express fully the difference in readi- 

 ness with which the chick responded. This series repeated 

 control series i with greater difference in the relative brightness 

 of the electric boxes. The conclusion seems to be justified, 

 on the basis of these results, that the chicks were responding 

 selectively to one of two objects of diff'erent size. Of course 

 the control of other possible determinants of reaction, such as 

 odor, would have made this conclusion more certain. The 

 small-large habit was now adopted to be used in conjunction 

 with the black-blue habit for an experimental test of the effects 

 and interrelation of habits. 



D. To What Extent Has Training General Value? 



After an experimental test of the influence of one labyrinth 

 habit upon the formation of another, Yerkes ' concludes that 

 " the acquisition of one form of labyrinth habit may facilitate 



1 Yerkes, R. M.: Op. cit., p. 2Q1. 



