Within recent years the doctrine that psychology is a science of
behavior has acquired a certain prominence. It is presupposed, of
course, that the behavior with which psychology is concerned is of a
distinctive sort; but the differentia is unfortunately the very thing
that the "behaviorist" has hitherto left out of account. In his revolt
against introspectionism, which has been accustomed to give to its
subject-matter a subjectivistic and "psychic" interpretation, he goes to
the other extreme and relies on behavior pure and simple. Being without
a serviceable differentia, he is unable to mark off the field of
psychology from contiguous territory. The selection of certain problems
within the general range of behavior, with no recognition of any
distinctive trait to guide and justify the selection, is hardly enough
to warrant a new science. Even an arbitrary principle of selection is
better than none, and it would, therefore, be quite as reasonable to
subdivide the field of botany in the interests of a new science, and
group together for separate botanical study those flowers which have
enabled poets to give symbolic expression to the beauty of women.
That the principle of selection is, in the end, the ability to modify
behavior through the anticipation of possible consequences, appears from
the fact that the category of stimulus and response is otherwise found
to be unworkable. It is true that in the simpler forms of behavior
stimulus and response may be correlated without practical difficulty.
But when we deal with what has been called "delayed overt response,"
the matter becomes more complicated and the theoretical difficulty
becomes more prominent. The behaviorist would not seriously undertake to
record everything that happens between stimulus and response. He
proceeds selectively, taking the relation of stimulus and response as
his clue. He is properly interested in the movements which result from
the application of the stimulus only in so far as they constitute
response. Otherwise his study is not a study of behavior, but a study of
movements. But when does a movement constitute a response? Do we label
as stimulus the spoken word which results in overt action a week later,
or the visual perception which sets a complicated and long-drawn-out
problem, for no other reason than that it appears somewhere as an
antecedent in the causal chain of events? If so, there is no obvious
reason why the event which occurred just before or immediately after the
_soi-disant_ stimulus should not be regarded as the true stimulus.
Unless a satisfactory reason is forthcoming, it would seem better to
substitute cause and effect for stimulus and response and to drop the
term behavior from our vocabulary. Psychology then becomes a study of
certain causal relationships, but is still without a principle for the
selection of those causal events which are supposed to constitute its
peculiar subject-matter.
Even if we manage to become reconciled to this situation, however, our
troubles are not yet at an end. There still remains the difficulty in
certain cases of showing that the event which is selected as stimulus or
cause bears any significant relationship to the event which figures in
our scheme as the response. The stimulus is supposed to have a causal
connection with the response, but how are we to know that this is the
fact? How are we to know that the engineer who solves a problem for me
at my request might not have done so anyway? No behaviorist can possibly
show that the air waves set in motion by my vocalization were an
indispensable stimulus. We doubtless believe that the spoken word was in
fact the spark which lit the fuse and finally exploded the mine, but
this belief involves a complication of causes which it is wholly beyond
our power to control or to verify.
It is true, of course, that we are able, as a matter of fact, to
correlate stimulus and response. I know that it was the spoken word
which caused the commission to be executed, for the expert reminds me of
the fact and presents a bill. But neither of us makes any pretense that
his belief is derived from a scrutiny of the causal sequence. Memory
furnishes us with a shortcut to the result. While our present acts are
doubtless connected with the past through causation, we do not regard
them as simply the effects of antecedent causes. They are rather
responses to present stimuli. The expert presents his bill, being moved
thereto by a stimulus which may be indicated by saying that it is the
spoken-word-constituting-a-commission-now-completed-and-entitling-me-
to-compensation. That is, the stimulus cannot be pushed back and
anchored at a fixed point in the past, but is a present factor at the
moment of response and is operative by virtue of its anticipation of
future events.
If, then, psychology is to be regarded as a study of behavior, it is
plainly necessary to reinterpret the category of behavior. For example,
a purely mechanical response to a light-stimulus may properly be viewed
as response to the ether-vibration or wave-length upon which it follows
in temporal sequence. But if this stimulation results in what is
commonly called consciousness, a different kind of response ensues. The
light-stimulus becomes a cause or occasion for the act of looking. But
why look, unless it be to secure a new stimulus for further response? We
stop to look, precisely because the first stimulus does not run smoothly
off the reel. The response will not go forward, but is halted and
expends itself in the effort to secure a further stimulus. This is the
moment of attention, in which the stimulus undergoes a process of
transformation, concomitantly with the process of reorganization in the
motor responses, and in the direction of ends or results that are
foreshadowed in it. This change in the stimulus takes place under
certain specifiable conditions, and the study of these conditions is a
study of such processes as perceiving, attending, remembering, and
deliberating, which are distinctively psychological in their nature.
Processes of this kind, if taken as changes in stimuli, find an
objective criterion in the adaptive behavior for the sake of which they
occur, and they provide psychology with a distinctive task and
subject-matter.
As against the introspectionist, then, the behaviorist is justified in
his contention that psychological procedure must be objective and
experimental in character. The danger to which he has exposed himself
is the failure to differentiate his problem from that of physiology and
physics. It is only by a proper recognition of both the objective and
the distinctive character of conscious behavior that psychology can free
itself of the reproach which is heaped upon it by members of its own
household and take the place that rightfully belongs to it in the
community of the sciences.