My chief observational task in Montecito was the study of ideational
behavior, or of such adaptive behavior in monkeys and apes as
corresponds to the ideational behavior of man. It was my plan to
determine, so far as possible in the time at my disposal, the existence
or absence of ideas and the rôle which they play in the solution of
problems by monkeys and apes. I had in mind the behavioristic form of
the perennial questions: Do these animals think, do they reason, and if
so, what is the nature of these processes as indicated by the
characteristics of their adaptive behavior?
My work, although obviously preliminary and incomplete, differs from
most of the previous studies of the complex behavior of the infrahuman
primates in that I relied chiefly upon a specially devised method and
applied it systematically over a period of several months. The work was
intensive and quantitative instead of more or less incidental, casual,
and qualitative as has usually been the case. Naturally, during the
course of my special study of ideational 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, I found time each day to get into intimate touch with the
free activities of my subjects and to observe their social relations and
varied expressions of individuality. As a result of my close
acquaintance with this band of primates, I feel more keenly than ever
before the necessity of taking into account, in connection with all
experimental analyses of behavior, the temperamental characteristics,
experience, and affective peculiarities of individuals.
The light which I have obtained on the general problem of ideation has
come, first, through a method which I have rather inaptly named the
multiple-choice method, and second, and more incidentally, through a
variety of supplementary methods which are described 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 during the past ten or fifteen years. It was not my aim to
repeat precisely the observations made by others, but instead to verify
some of them, and more especially, to throw additional light on my main
problem and to further the analysis of complex behavior.
What has been referred to as the multiple-choice method was devised by
me three years ago as a means of obtaining strictly comparable objective
data concerning the problem-solving ability of various types and
conditions of animals. The method was first tried with human subjects in
the Psychopathic Hospital, Boston, with a crude keyboard apparatus
which, however, proved 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 results to the study of the
characteristics of ideational behavior in human defectives,--children,
and adults,--and in subjects afflicted with various forms of mental
disease. It is at present being tried out as a practical test in
connection with vocational guidance and various forms of institutional
examination, such as psychopathic hospital and court examinations.
As no adequate description of the method has yet been published to which
I can here refer, it will be necessary to present its salient
characteristics along with a description of the special form of
apparatus which was found suitable for use with monkeys and apes.
The method is so planned as to enable the observer to present to any
type or condition of organism which he wishes to study any one or all of
a series of problems ranging from the extremely simple to the complex
and difficultly soluble. All of the problems, however, are completely
soluble by an organism of excellent 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 perception of a
certain constant relation among a series of objects to which the subject
is required to attend and respond. Such relations are, for example,
secondness from one end of the group, middleness, simple alternation of
ends, or progressive movement by constant steps from one end of a group
to the other.
It is possible to present such relational problems by means of
relatively simple reaction-mechanisms. In their essential features, all
of the several types of multiple-choice apparatus designed by the writer
and used either by him or by his students and assistants are the same.
They consist of a series of precisely similar reaction-devices, any one
or all of which may be used in connection with a given observation.
These reaction-mechanisms are so chosen as to be suited to the structure
and action-system of the animal to be studied. For the human being the
mechanism consists of a simple key and the total apparatus is a bank of
keys, with such electrical connections as are necessary to enable the
observer to obtain satisfactory records of the subject's behavior. Let
us suppose the bank of keys, as was actually the case in my first form
of apparatus, to consist of twelve separate 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 other keys in the group. On the completion of a subject's
reaction to the group of three keys, a group of seven keys at the
opposite end of the keyboard may, for example, be presented. Similarly,
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.