226 The Animal Mind 



plain colors. Von Frisch (247) finds that bees can dis- 

 criminate patterns like those of flowers, but fail with those 

 very unlike flower patterns. This evidence, taken at its 

 face value, indicates that the compound eye is able to 

 furnish a fairly clear image, and not merely discrimina- 

 tions of light direction and movement. 



Among vertebrates, various species of birds were experi- 

 mented on by the method of placing cards carrying simple 

 designs over glasses covered with gray paper, food being 

 found always under the same card. The English sparrow 

 and the cowbird both learned to distinguish a card bearing 

 three horizontal bars and one bearing a black diamond 

 from each other and from plain gray cards. On the other 

 hand, the sparrow, curiously enough, did not succeed in dis- 

 criminating vessels of different form ; the cowbird was not 

 fully tested with these, but gave some evidence of learning 

 (6 10, 611). Pigeons were only moderately successful in 

 a similar test (647). Breed (101, 102) and Bingham (56) 

 investigated the form discriminations of the chick, using 

 the more accurate method of offering a choice between 

 compartments illuminated through openings of different 

 forms. One out of three of Breed's chicks succeeded in 

 discriminating between a circle and a square : Bingham's 

 chicks distinguished between a circle and a triangle when 

 the apex of the triangle was on top, but the discrimination 

 broke down when the triangle had its base uppermost. 

 The most careful work that has been done on the discrimi- 

 nation of forms or patterns by animals, up to the date of 

 publication of this book, is that of Johnson (386). His 

 apparatus allowed the presentation of two illuminated 

 fields whose intensity could be perfectly controlled, with 

 black bands across them whose width could be varied at 

 will. He proposed four problems : (i) the width of stripes 



