70 FREDERICK S. BREED 



ally exclude each other ? But only in so far as a positive reaction 

 essentially includes a negative one and vice versa, W' affirmation 

 psychologically negation. 



There still remains another aspect of the relation between 

 rejecting and accepting, their possible necessary concomitance. 

 But if, with innervation of a given motor center, there is, accord- 

 ing to the MuensterbergiaijL action theory, a simultaneous inhibi- 

 tion of the antagonistic motor center, we are bound to think 

 of real affirmation and real negation as distinct fimctions, for 

 inhibition is not negation. 



What, then, shall we say of our method as a " discrimina- 

 tion method? " From the point of view of behavior discrimi- 

 nation is selective reaction. In this sense the Yerkes method 

 is a discrimination method. 



It is interesting to observe the result when neither black nor 

 blue are in the test combination presented after the training. 

 No. 44 on May 22 completed the black-blue habit with three 

 errorless series. On June 6 its persistence test was black, 10; 

 blue, o. The same day its preference tests on orange-white 

 resulted 5-5. The daily training on orange-white, continued from 

 this date, progressed as follows: 7-3, 8-2, 7-3, lo-o, lo-o, 

 lo-o. No. 43, the same age, began black-blue training on the 

 same date as no. 44 and completed the work the day after no. 

 44 with three perfect series. Its persistence test on June 6 

 resulted also lo-o. But when tested on the same day for its 

 orange-white preference prior to the training on this combina- 

 tion, its record was orange, 10, white, o. The figures thereafter 

 were 9-1, 9-1, 9-1, lo-o, lo-o, lo-o. It is apparent in both 

 these cases that the black-blue training strikingly predisposed 

 the chicks to react positively to the darker of the two stimuli 

 in the second combination. It cannot be, urged in regard to no. 

 44 that, either on account of ready modifiability or an easy 

 combination, this was simply a case of rapid learning unassisted 

 by the previous acquisition, first, because orange-white, as indi- 

 cated by earlier tests, is not so easy a combination; and secondly; 

 the rate of acquisition by this chick was only average, nine 

 days' training having been required for it to complete the black- 

 blue habit. 



The important exception to the general rule for brightness 

 training, namely, that when the color which the chick was 



