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Abstract:
Several researchers have proposed dichotomies suggesting that
the two hemispheres are biased toward processing different aspects
of a visual stimulus. The implication of each of these dichotomies
is that the analysis of a visual input may be divided between the
two hemispheres, with each contributing its expertise to the final
percept. In a series of experiments, we investigated the abilities
of two callosotomy patients to compare stimuli presented within a
visual field. For judgments about line orientation and vernier
offset, the right hemisphere was superior to the left in both
patients. For judgments about relative size, one patient showed a
right hemisphere advantage and the other showed hemispheric
equivalence. In making judgments about luminance of stimuli, there
was no hemispheric difference evident in either callosotomy
patient. We hypothesized that this pattern of results was due to a
right hemisphere superiority for spatial processing. The second set
of experiments was designed to investigate the abilities of the
divided hemispheres to match the same stimuli based on either
identity or spatial position. For judgments about spatial position,
the right hemisphere was superior to the left. In contrast, the
left hemisphere showed a tendency to perform better than the right
on judgments about stimulus identity. We concluded that this
pattern of results was due to a left hemisphere specialization for
pattern recognition and a right hemisphere specialization for
processing spatial relationships.
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