The Mental Life of Monkeys and Apes | Page 7

were 18 inches wide, by 5 feet
high, while those in the alleyways were 24 inches wide by 6 feet high.
The response-compartment E of figure 17 was 14 feet 4 inches, by 8
feet, by 6 feet in depth. In order that the apparatus might be used with
adult human subjects conveniently, if such use should prove desirable,
the depth throughout was made 6 feet, and it was therefore possible for
the experimenter to walk about erect in it.
The experimental procedure was briefly as follows: A small quantity of
food having been placed in each of the food cups and covered by the
metal flanges on the exit doors, the experimenter raised door 11 of
figure 17 and then opened door 10 and the door of the cage in which
the desired subject was confined. After the latter, in search of food, had
entered the runway D, the experimenter lowered door 11 to keep it in
this runway, and immediately proceeded to set the
reaction-mechanisms for an experiment (trial). Let us suppose that the
first setting to be tried involved all of the nine boxes. Each of the
entrance doors would therefore be raised. Let us further suppose that
the right door is defined as the middle one of the group. With the
apparatus properly set, the experimenter next raises door 12, thus
admitting the animal to the response-compartment E. Any one of the
nine boxes may now be entered by it. But if any except number 5, the
middle member of the group, be entered, the entrance door is
immediately lowered and both the exit and entrance doors locked in
position so that the animal is forced to remain in the box for a stated
period, say thirty seconds. At the expiration of this time the entrance
door is raised and the animal allowed to retrace its steps and make
another choice. When the middle box is chosen, the entrance door is
lowered and the exit door immediately raised, thus uncovering the food,
which the animal eats. As a rule, by my monkeys and ape the reward
was eaten in the alleyway G instead of in the multiple-choice box. As
soon as the food has been eaten, the exit door is lowered by the
experimenter, and the animal returns by way of G and H to runway D,
where it awaits its next trial.
As rewards, bananas and peanuts were found very satisfactory, and
although occasionally other foods were supplied in small quantities,
they were on the whole less constantly desired than the former.
Four problems which had previously been presented to other organisms

were in precisely the same form presented to the three primates. These
problems may be described, briefly, by definition of the right reaction
mechanism, thus: problem 1, the first mechanism at the subject's left;
problem 2, the second mechanism at the subject's right (that is, from the
end of the series at the subject's right); problem 3, alternately, the first
mechanism at the subject's left and the first at its right; problem 4, the
middle mechanism of the group.
It was my intention to present these four problems, in order, to each of
the three animals, proceeding with them as rapidly as they were solved.
But as it happened, only one of the three subjects got as far as the
fourth problem. When observations had to be discontinued, Sobke was
well along with the last, or fourth problem; Skirrl was at work at the
third problem; and Julius had failed to solve the second problem.
For each of the problems, a series of ten different settings of the doors
was determined upon in advance. These settings differ from those
employed in a similar investigation with the pig only in that the
numbering of the doors is reversed. In the present apparatus, the boxes
as viewed from the front (entrance) are numbered from the left to the
right end, whereas those of the pig apparatus were numbered from the
right end to the left end.
Below are presented for each of the several problems (1) the numbers
of the settings presented in series; (2) the numbers of the doors open; (3)
the number of doors open in each setting and for the series of ten
settings; and (4) the number of the right door.

PROBLEM 1. First mechanism at left of group
Doors No. of No. of Settings open doors open right door
1..................1.2.3......................3..................1
2..................8.9........................2..................8
3..................3.4.5.6.7..................5..................3
4..................7.8.9......................3..................7
5..................2.3.4.5.6..................5..................2
6..................6.7.8......................3..................6
7..................5.6.7......................3..................5
8..................4.5.6.7.8..................5..................4
9..................7.8.9......................3..................7
10..................1.2.3......................3..................1 -- Total 35

PROBLEM 2. Second mechanism from the right end of group
Doors No. of No. of Settings open doors open right door
1..................7.8.9......................3..................8
2..................1.2.3.4....................4..................3
3..................2.3.4.5.6.7................6..................6
4..................1.2.3.4.5.6................6..................5
5..................4.5.6.7.8..................5..................7
6..................1.2.3......................3..................2
7..................2.3.4.5....................4..................4
8..................1.2.3.4.5.6.7.8.9..........9..................8
9..................1.2.3.4....................4..................3
10..................3.4.5.6.7.8................6..................7 -- Total 50
PROBLEM 3. Alternately the first mechanism at the left and the first at
the right