The Mental Life of Monkeys and Apes | Page 5

the subject is required to discover
with the minimum number of trials the correct reaction-mechanism.
Thus, time after time, the experimenter presents a different group of
keys so that the subject in no two successive trials is making use of the
same portion of the keyboard. It is therefore impossible for him to react
to spatial relations in the ordinary sense and manner, and unless he can
perceive and appropriately respond to the particular relation which
constitutes the only constant characteristic of the correct
reaction-mechanism for a particular problem, he cannot solve the
problem, or at least cannot solve it ideationally and on the basis of a
small number of observations or trials.
For the various infrahuman animals whose ideational behavior has been
studied by means of this method, it has been found eminently
satisfactory to use as reaction-mechanisms a series of similar boxes,
each with an entrance and an exit door. An incentive to the selection of
the right box in a particular test is supplied by food, a small quantity of
which is placed in a covered receptacle beyond the exit door of each of
the boxes. Each time an animal enters a wrong box, it is punished for
its mistake by being confined in that box for a certain period, ranging
from five seconds to as much as two minutes with various individuals
or types of organism. This discourages random, hasty, or careless
choices. When the right box is selected, the exit door is immediately
raised, thus uncovering the food, which serves as a reward. After eating
the food thus provided, the animal, according to training, returns to the
starting point and eagerly awaits an opportunity to attempt once more
to find the reward which it has learned to expect. With this form of the
apparatus, the boxes among which choice may be made are indicated
by the raising (opening) of the front door.
Since with various birds and mammals the box form of apparatus had
proved most satisfactory, I planned the primate apparatus along similar
lines, aiming simply to adapt it to the somewhat different motor
equipment and destructive tendencies of the monkeys. I shall now

briefly describe this apparatus as it was constructed and used in the
Montecito laboratory.

EXPLANATION OF PLATE IV
FIGURE 13.--Multiple-choice apparatus, showing observer's bench and
writing stand. FIGURE 14.--Apparatus as seen from observer's bench.
FIGURE 15.--Entrances to multiple-choice boxes as seen from the
response-compartment. FIGURE 16.--Apparatus as seen from the rear,
showing exit doors, food receptacles, and covers for same.

The apparatus was built in room A (figure 12), this room having been
especially planned for it with respect to lighting as well as dimensions
and approaches. It was unfortunately impossible to obtain photographs
showing the whole of the apparatus, but it is hoped that the four partial
views of plate IV may aid the reader who is unfamiliar with previously
described similar devices to grasp readily the chief points of
construction. In this plate, figure 13 shows the front of the complete
apparatus, with the alleyway and door by way of which the
experimenter could enter. The investigator's observation-bench and
record-table also appear in this figure, together with weighted cords
used to operate the various doors and the vertically placed levers by
means of which each pair of doors could be locked. Figure 14 is the
view presented to the observer as he stood on the bench or observation
stand of figure 13 and looked over the entire apparatus. Three of the
entrance doors are shown at the right of this figure as raised, whereas
the remainder of the nine entrance doors of the apparatus are closed.
Figure 15 is a view of the entrance doors from below the wire roof of
the apparatus. Again, two of the doors are shown as raised, and three
additional ones as closed. The rear of the apparatus appears in figure 16,
in which some of the exit doors are closed and others open. In the latter
case, the food receptacles appear, and on the lower part of the raised
doors of the corresponding boxes may be seen metal covers for the
food receptacles projecting at right angles to the doors, while on the
lower edge of each door is an iron staple used to receive a sliding bar
which could be operated from the observer's bench as a means of
locking the doors after they had been closed. The space beyond the exit

doors was used as an alleyway for the return of the animals to the
starting point.
It will be necessary at various points in later descriptions to refer to
these several figures. But further description of them will be more
readily appreciated after a careful examination of the ground plan of the
apparatus presented as figure 17 In accordance