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General Discussion
Three experiments examined the effects of a task-irrelevant auditory stimulus on
somatosensory perception. In Experiment 1, a simultaneously presented auditory
stimulus increased sensitivity to a near-threshold touch stimulus. Experiment 2 showed
that the enhancing effects of sounds on touch perception are spatially specific; only
sounds that occurred on the same side as the touch enhanced spatial discrimination. In
Experiment 3, a somatosensory stimulus containing frequency was used to show that
the effects of sound on touch are frequency-dependent: discrimination performance
increased when a sound was the same frequency as the tactile stimulus and decreased
Whenthesoundwasofadifferentfrequency.
All three experiments show a significant effect of sound on touch perception,
even though different experimental paradigms were used. This consistency is important
because it demonstrates the robustness of the auditory influences on touch perception,
and suggests that there are likely to be a variety of interesting neural interactions
underlying these behavioral effects. For instance, Experiment 1 shows that simultaneous
sound enhances somatosensory perception, with the increases in d' indicating that the
effect is not due to a response bias. However, the results of Experiment 1 could have
been due to an increase in arousal, which could arise from a simultaneous stimulus in
any modality (not necessarily auditory-somatosensory). But Experiment 2 shows that
the interaction between audition and Somatosensation is spatially Iateralized, with
signal detection analyses confirming that this Iateralized enhancement was not a
consequence of a response bias. These results suggest neural interactions occurring in