Why should there be such a difference? A proponent of the ‘‘great man’’
theory of history might argue that it was because the fathers of Gestalt psy-
chology, who opened up the whole question of perceptual organization, had
focused on vision and never quite got around to audition.
However, it is more likely that there is a deeper reason. We came to know
about the puzzles of visual perception through the arts of drawing and paint-
ing. The desire for accurate portrayal led to an understanding of the cues for
distance and certain facts about projective geometry. This was accompanied by
the development of the physical analysis of projected images, and eventually
the invention of the camera. Early on, the psychologist was faced with the dis-
crepancy between what was on the photograph or canvas and what the person
saw.
The earlier development of sophisticated thinking in the field of visual per-
ception may also have been due to the fact that it was much easier to create a
visual display with exactly specified properties than it was to shape sound in
equally exact ways. If so, the present-day development of the computer analy-
sis and synthesis of sound ought to greatly accelerate the study of auditory
perception.
Of course there is another possibility that explains the slighting of audition in
the textbook: Perhaps audition is really a much simpler sense and there are no
important perceptual phenomena like the visual constancies to be discovered.
This is a notion that can be rejected. We can show that such complex phe-
nomena as constancies exist in hearing, too. One example is timbre constancy.
A friend’s voice has the same perceived timbre in a quiet room as at a cocktail
party. Yet at the party, the set of frequency components arising from that voice
is mixed at the listener’s ear with frequency components from other sources.
The total spectrum of energy that reaches the ear may be quite different in dif-
ferent environments. To recognize the unique timbre of the voice we have to
isolate the frequency components that are responsible for it from others that are
present at the same time. A wrong choice of frequency components would
change the perceived timbre of the voice. The fact that we can usually recog-
nizethetimbreimpliesthatweregularlychoosetherightcomponentsindif-
ferent contexts. Just as in the case of the visual constancies, timbre constancy
will have to be explained in terms of a complicated analysis by the brain, and
not merely in terms of a simple registration of the input by the brain.
There are some practical reasons for trying to understand this constancy.
There are engineers currently trying to design computers that can understand
what a person is saying. However, in a noisy environment the speaker’s voice
comes mixed with other sounds. To a naive computer, each different sound that
the voice comes mixed with makes it sound as if different words were being
spoken or as if they were spoken by a different person. The machine cannot
correct for the particular listening conditions as a human can. If the study of
human audition were able to lay bare the principles that govern the human
skill, there is some hope that a computer could be designed to mimic it.
The Problem of Scene Analysis
It is not entirely true that textbooks ignore complex perceptual phenomena in
audition. However, they are often presented as an array of baffling illusions.^1
214 Albert S. Bregman