80 EUPHA FOLEY TUGMAN 



(2) Previous experimental work. — Considerable work has been 

 done in experimenting on the learning methods and capacities 

 of animals, from amoeba to man. Only recently, however, have 

 investigators begun to study the delicacy and completeness of 

 the sensory equipment of animals. Of most importance in con- 

 nection with the present investigation is the work of Breed, 1 

 Cole, 2 and Bingham 3 on chicks, and Porter 4 ' 5 on birds. 



Breed 1 used the discrimination method in experimenting with 

 chicks. His results show that his chicks could discriminate 

 between black and white, different colors, and two objects of 

 different size. He made form tests also, but his chicks gave 

 negative results. 



Cole 2 used the discrimination method in studying " the rela- 

 tion of strength of stimulus to the rate of learning in the chick." 

 His results seem to indicate that when discrimination is easy 

 the number of trials necessary for learning is less than when the 

 discrimination is difficult. 



Bingham 3 experimented on size and form perception. His 

 chicks were punished by electric shocks when they made a wrong 

 choice, and were rewarded with " food, light, warmth, and com- 

 panionship " when they discriminated properly and were thus 

 able to reach their nest box. He found that " the chicks' thresh- 

 old of difference in size perception lies between one-fourth and 

 one-sixth when the diameter of the standard circle is 6 cm." 

 He holds that " earlier experimenters on the chick's perception 

 of forms have failed to eliminate all possible conditions for dis- 

 crimination other than the factor of form. * * * Reactions 

 to optical stimuli which have been interpreted by observers as 

 indicating form discrimination are probably made on the basis 

 of unequal stimulation of different parts of the retina. * * 



1 Breed, F. S. The Development of Certain Instincts and Habits in Chicks. 

 Behavior Mono., vol. 1, No. 1, Nov. 1, 1911. 



2 Cole, L. W. The Relation of Strength of Stimulus to Rate of Learning in 

 Chicks. Journal of Animal Behavior, vol. 1, No. 1, 1911. Page 111. 



3 Bingham, H. C. Size and Form Perception in Gallus Domesticus. Journal of 

 Animal Behavior, vol. 3, No. 2, 1913. Page 65. 



4 Porter, J. P. A Preliminary Study of the English Sparrow and Other Birds. 

 Amer. Jour, of Psych., vol. 13, 1904. Page 313. 



'Porter, J. P. Further Study of the English Sparrow and Other Birds. Amer. 

 Jour, of Psych., vol. 17, 1906. Page 248. 



