The Mental Life of Monkeys and Apes: A Study of Ideational Behavior

o determine, so far as possible in the time at my disposal, the existence or absence of ideas and the r?le which they play in the solution of problems by monkeys and apes. I had in mind the beha

ional behavior observations were made relative to various other aspects of the life of my subjects. Such, for example, are my notes on the use of the hands, the instincts, the emotions, and the natural aptitudes of individuals. It is, indeed, impossible to observe any of the primates without noting most interesting and illuminating activities. And although the major portion of my time was spent in hard and monotonous work with my experimental apparatus

escribed in Section IV of this report. These supplementary methods are simple tests of ideation rather than systematic modes of research. They differ from my chief method, among other respects, in that they have been used by various investigators durin

oved wholly satisfactory as a means of demonstrating its value. It has since been applied by means of mechanisms especially adapted to the structure and activities of the organisms, to the study of the behavior of the crow, pig, rat, and ringdove (Yerkes, 1914; Coburn and Yerkes, 1915; Yerkes and Coburn, 1915). The method has also been applied with most gratifying

r, it will be necessary to present its salient characteristics along with a description

cellent ideational ability. For the human subject, the solution of the easiest problem of all requires almost no effort, whereas even moderately difficult problems may require many repetitions of effort and hours or days of application to the task. In each case, the solution of the problem depends upon the pe

te reaction-mechanisms; and let us suppose, further, the constant relation (problem) on the basis of which the subject is required to react to be that of middleness. It is evident that in successive trials or experiments the keys must be presented to the subject in odd groups, the possibilities being groups of 3, 5, 7, 9, or 11. If for a particular observation the experimenter wishes to present the first three keys at the left end of the keyboard, he pushes back the remaining nine keys so that they cannot be operated and requires the subject to select from the group of three keys the one which on being pressed causes a signal to appear. It is of course the clearly understood task of the subject to learn to select the correct key in the group on first trial. This becomes possible only as the subject observes the relation of the key which produces the desired effect to the othe

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, t

atus along similar lines, aiming simply to adapt it to the somewhat different motor equipment and destructive tendencies

TION OF

een from observer's bench. FIGURE 15.-Entrances to multiple-choice boxes as seen from the response-compartm

so 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

ge cage Z, from which he has direct access to the animals and can bring them into the apparatus. The multiple-choice mechanism proper, consisting of nine similar boxes (nine were used instead of twelve as a matter of convenience of construction, not because this smaller number is otherwise preferable) is labelled F. These boxes are numbered 1 to 9, beginning at the left. This numbering was adhered to in the

nd anthropoid apes,-hence the apparent cumbersomeness of certain portions. It was equally necessary to provide for the protection of

re carried by pulleys appropriately placed above the apparatus. Each weight was so chosen as to be just sufficient to hold its door in position after the experimenter had raised it. For the convenienc

etting. No such windows were necessary in the exit doors, but to them were attached heavy galvanized iron flanges which served to cover the food receptacles. One of these flanges is labelled o in figure 17. The food receptacles were provided by boring holes in a 2 by 4

plan of multiple-choice apparatus

ing from boxes to starting point at D; I, alleyway used by experimenter as approach to rear of apparatus; W, W, windows; P, alleyway; Z, large cage; 16, entrance to room A; 17, entrance to a

essary to introduce locking devices which could be operated by the experimenter from the observation bench. This was readily accomplished by cutting holes in the floor, which permitted an iron staple, screwed to the lower edge of each door, to project through the floor.

and G 30 inches wide, by 6 feet deep. The doors of the several boxes 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

l 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 peri

although occasionally other foods were supplied in small quantitie

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 e

lved. But as it happened, only one of the three subjects got as far as the fourth problem. When observations had to be discontinued, Sobke

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 th

resented in series; (2) the numbers of the doors open; (3) the number of doors open in

st mechanism a

No. of

en doors op

.3....................

......................

.5.6.7................

.9....................

.4.5.6................

.8....................

.7....................

.6.7.8................

.9....................

2.3...................

ta

mechanism from the

No. of

en doors op

.9....................

.3.4..................

.4.5.6.7..............

.3.4.5.6..............

.6.7.8................

.3....................

.4.5..................

.3.4.5.6.7.8.9........

.3.4..................

4.5.6.7.8.............

ta

ly the first mechani

e right end

No. of

en doors op

.7....................

.7....................

.3.4.5.6..............

.3.4.5.6..............

.6.7.8................

.6.7.8................

.4.5..................

.4.5..................

.5.6.7.8.9............

4.5.6.7.8.9...........

ta

ddle mechanis

No. of

en doors op

.4....................

.7.8.9................

.3.4.5.6.7............

.9....................

.6.7.8................

.3.4.5.6.7.8.9........

.3....................

.4.5.6................

.5.6.7.8.9............

7.8...................

ta

he subject had learned to choose the correct door by memorizing each particular setting. These supplementary observations may be known as control experim

or Control

. First a

No. of

en doors op

.4....................

.8.9..................

.5....................

.6.7.8.9..............

.8.9..................

.3.4.5................

.4.5.6.7.8............

.5.6.7.8..............

.7....................

2.3.4.5.6.7.8.9.......

Second fr

No. of

en doors op

.7.8..................

.4.5.6................

.3.4.5.6.7.8.9........

.7....................

.3.4..................

.6....................

.4.5..................

.3....................

.3.4.5.6.7............

3.4.5.6.7.8.9.........

ternate left

No. of

en doors op

......................

......................

.6.7.8.9..............

.6.7.8.9..............

.3.4.5................

.3.4.5................

.4.5.6.7..............

.4.5.6.7..............

.5.6.7.8..............

4.5.6.7.8.............

EM 4.

No. of

en doors op

.6.7.8................

.3....................

.3.4.5.6.7.8.9........

.4.5.6................

.8....................

.5.6.7.8.9............

.9....................

.3.4.5.6.7............

.4....................

4.5.6.7...............

ary to present only five of the series of ten settings in succession and then to interrupt observations for an interval of a few minutes or even several hours. But as a rule it was possible to present the series of ten settings. All things being considered, it proved more satisfactory to give only ten