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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, many
individuals identify a single sound. When the octave is repeatedly
alternated, with the ear that previously received the high tone now
receiving the low tone, and vice versa, most individuals perceive a
shifting pitch that alternates its position between the ears.
Deutsch (1975) has proposed that this illusion arises from the
extraction of incongruent pitch and position information from the
pure tone components. To examine this hypothesized mechanism, we
used the tones that generate the octave illusion as forward
maskers. We observed that, when embedded within a sequence of
repeating dichotic octaves or the octave illusion, the masking
potential of the components dramatically increases, in some
conditions more than tripling. However, little difference has been
noted between the level and shape of masking achieved during the
octave illusion and that evoked during control conditions matched
for sequence length. This suggests that it is primarily the
repeated presentation of tones during the octave illusion, rather
than alternating dichotic octaves, that influences the
representation of the components. The considerable magnitude of
this repetition effect implies the involvement of selective
attention in forming or reinforcing the octave illusion.
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