The Mental Life of the Monkeys 201 
Fig. 29 gives facsimiles of the different signals reduced to 
one sixth their actual size. The drawing of 1o1 is not accu- 
rate, the outer ring being too thick. 
EXPERIMENTS WITH No. 2 
I first secured the partial formation of the habit of coming 
down when I took a bit of food in my hand. I then used the 
apparatus for exposing cards, YES in front being the ‘ yes’ 
signal and a circle at the back being the ‘no’ signal. I gave 
No. 2 25 trials with the ‘yes’ signal and then began a regular 
“ieee 
RighthandA. Left hand A Box near 
Palm upB E E 
Held up 
A b. 
Low front 
Fic. 31. 
experiment similar to those described. After about go trials 
(November 9-12, 1900) there was no progress toward differ- 
entiation of response, and it was evident from No. 2’s be- 
havior that he was reacting solely to the movements of my 
hand. So I abandoned the exposing apparatus and used 
(November 11-13, 1900) as the ‘yes’ signal the act of taking 
the food with my left hand from a pile on the front of the box 
and for the ‘no’ signal the act of taking food with my right 
hand from a pile 4 inches behind that just mentioned. 
