Animal intelligence: Experimental studies

by Edward L. Thorndike

[Fig. 29] gives facsimiles of the different signals reduced to one sixth their actual size. The drawing of 101 is not accurate, the outer ring being too thick.

Experiments with No. 2

Fig. 31.

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 experiment similar to those described. After about 90 trials (November 9-12, 1900) there was no progress toward differentiation of response, and it was evident from No. 2’s behavior 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. No. 2 did come to differentiate these two signals. The record of his progress is given in [Fig. 31] by A and A₁.

I then made a second attempt with the exposing apparatus, using cards 2 and 102 (November 6, 14-21). No. 2 did react to my movements in pulling the string but in over 100 trials made no progress in the direction of a differential reaction to the ‘no’ signal. I then tried feeding him at each signal, feeding him at the bottom of the cage as usual when I gave the ‘yes’ signal and at the top when I gave the ‘no’ signal. After a hundred trials with the ‘no’ signal there was no progress.

I then abandoned again the exposing apparatus and used as signals the ordinary act of taking food with my left hand (yes) and the act of moving my left arm from my right side round diagonally (swinging it on my elbow as a center) and holding the hand, after taking the food, palm up (no) (November 26, 27, 1900). No. 2 did come to differentiate these signals. His progress is given in the diagram in [Fig. 31] entitled ‘Palm up’ (B).

I next used (November 27, 1900) as the ‘yes’ signal the same act as before and for the ‘no’ signal the act of holding the food just in front of the box about four inches below the edge. No. 2’s progress is shown in [Fig. 31] in the diagram entitled ‘low front’ (C and C₁).

I next used (November 27-30) the same movement for both ‘yes’ and ‘no’ signals save that as the ‘yes’ signal I took the food from a brown pasteboard box 3 by 3 by 0.5, and as the ‘no’ signal I took it from a white crockery cover two inches in diameter and three eighths of an inch high which was beside the box but three inches nearer me. No. 2’s progress is shown in [Fig. 31] in the diagram entitled ‘Box near’ (D).

I next used for the ‘yes’ signal the familiar act and for the ‘no’ signal the act of holding the food six inches above the box instead of a quarter or a half an inch. The progress is shown in [Fig. 31], E and E₁. I then tried taking the food from a saucer off the front of the box for the ‘yes’ signal and from a small box at the back for the ‘no’ signal. ‘Yes’ was perfect from the start (10 trials given). ‘No’ was right once, then wrong once, then right for the remaining eight.