198 Animal Intelligence 



of an actual retrograde as the trials concerned followed an 

 eight days' cessation of the experiments. 



I next tried No. i with an apparatus exposing sometimes 

 a card with a diamond-shaped piece of buff-colored paper 

 on it and sometimes a card with a similar black piece. 

 The black piece was three fourths of an inch farther behind 

 the opening than the other. The light color was the ' yes ' 

 signal. The error curves for both signals are given, as No. i 

 at the beginning of the experiment did not go down always 

 (Fig. 30, b and bj. 



I next tried No. i with the same apparatus but exposing 

 cards with YES and N in place of the buff and black dia- 

 monds. The record of the errors is given in Fig. 30, c and c x . 

 At the start he came down halfway very often. This I 

 arbitrarily scored as an error no matter which signal it 

 was in response to. It should not be supposed that these 

 curves represent two totally new associations. It seems 

 likely that the monkey reacted to the position of the N 

 card in the apparatus (the same as that of the black dia- 

 mond card) rather than to the shape of the letters. On 

 putting the black diamond in front he was much confused. 



I next gave No. i the chance to form the habits of coming 

 down when I rapped my pencil against the table twice and 

 of staying where he was when I rapped with it once. He 

 had 90 trials of each signal but failed to give evidence of 

 any different associations in the two cases. 



Experiments of this sort were discontinued in the summer. 

 In October I tried No. i with the right and left hand ex- 

 periment, he being in a new room and cage, and I being 

 seated in a different situation. He came down at both sig- 

 nals and failed to make any ascertainable progress with the 

 no signal in 80 trials. (October 20-24.) 



I then tried him with the black and buff diamonds, the 



