posed by Mari Reiss Jones, that is best understood as describing the influence
of schemas on stream segregation.
Verification of the Theory
The theory presented in this chapter proposes that there is an auditory stream-
forming process that is responsible for a number of phenomena such as the
streaming effect and the illusion of continuity, as well as for the everyday
problems of grouping components correctly to hear that a car is approaching
as we cross a street, or ‘‘hearing out’’ a voice or an instrument from a musical
performance. This is not the type of theory that is likely to be accepted or
rejected on the basis of one crucial experiment. Crucial experiments are rare in
psychology in general. This is because the behavior that we observe in any
psychological experiment is always the result of a large number of causal fac-
tors and is therefore interpretable in more than one way. When listeners par-
ticipate in an experiment on stream segregation, they do not merely perceive;
they must remember, choose, judge, and so on. Each experimental result is al-
ways affected by factors outside the theory, such as memory, attention, learn-
ing, and strategies for choosing one’s answer. The theory must therefore be
combined with extra assumptions to explain any particular outcome. Therefore
it cannot easily be proven or falsified.
Theories of the type I am proposing do not perform their service by predict-
ing the exact numerical values in experimental data. Rather they serve the role
of guiding us among the infinite set of experiments that could be done and
relationships between variables that could be studied. The notion of stream
segregation serves to link a number of causes with a number of effects. Stream
segregation is affected by the speed of the sequence, the frequency separation of
sounds, the pitch separation of sounds, the spatial location of the sounds, and
many other factors. In turn, the perceptual organization into separate streams
influences a number of measurable effects, such as the ability to decide on the
order of events, the tendency to hear rhythmic factors within each segregated
stream, and the inability to judge the order of events that are in different
streams. Without the simplifying idea of a stream-forming process, we would
be left with a large number of empirical relations between individual causal
influences and measurable behaviors.
A theory of this type is substantiated by converging operations. This means
that the concepts of ‘‘perceptual stream’’ and ‘‘scene-analysis process’’ will gain
in plausibility if a large number of different kinds of experimental tasks yield
results that are consistent with these ideas.
Summary
I started this chapter with a general introduction to a number of problems. I
began with the claim that audition, no less than vision, must solve very com-
plex problems in the interpretation of the incoming sensory stimulation. A
central problem faced by audition was in dealing with mixtures of sounds.
The sensory components that arise from distinct environmental events have to
be segregated into separate perceptual representations. These representations
246 Albert S. Bregman