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Abstract:
Abstract: The octave illusion presents a significant
challenge to our understanding of auditory processing. When two
pure tones separated by an octave are presented simultaneously, one
to each ear, most individuals identify a single source. When the
octave is repeatedly alternated, such that the ear that previously
received the high tone now receives the low tone, and vice versa,
participants perceive a shifting pitch that alternates its position
from one ear to the other. Deutsch (1975, JASA) has proposed that
this illusion arises from the extraction of incongruent pitch and
position information from these sinusoidal components. We have
tested this model by using the components that generate the octave
illusion as forward maskers. This method generates psychophysical
tuning curves -- representations of the frequency components that
make up each dichotic octave -- and has provided a new perspective
on the peripheral and central mechanisms that combine to generate
the pitch disparity. A binaural masking level difference paradigm
was also adopted to map the spatial representation of the octave
components and determine how these are integrated to generate
laterality effects in the illusion. Across both experiments, our
results have implications for the central postulate of Deutsch's
model that, despite perceptual fusion of dichotic octaves in single
sources, it is the conservation of frequency and spatial
information in the most basic components that drives the octave
illusion.
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