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Abstract:
Research with neuropsychological patients has led to reports
of category-specific deficits in some patient populations. However,
some of these results may have arisen due to stimuli artefacts, for
example frequency of occurrence, or perceptual cues in studies
using pictures. Therefore, rigorous testing of stimuli on normal
populations is required before such stimuli are used for
investigation of patient groups. Recently, category differences in
processing have also been reported in semantic tasks with healthy
participants. The present study investigates the performance of
healthy young adults on word stimuli controlled for frequency to
explore ontological category processing. Dense array (128 channels)
event related potentials (ERPs) were recorded in order to examine
any electrophysiological differences in ontological category
processing. A category verification task was completed by 18 young
adults. The stimulus onset asynchrony was 1000ms. Natural and
man-made stimuli were equated for frequency of occurrence and word
length. The results demonstrated significant priming effects for
both natural and man-made stimuli. However, the magnitude of the
absolute priming effects was larger for natural than man-made
stimuli. Topographical differences of the N400 component were also
demonstrated. These converging results support the hypothesis that
natural and man-made category items are not processed equivalently
in young adults.
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