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Abstract:
Abstract: Evidence from neuropsychology and functional
neuroimaging suggests that dissociable neural systems are involved
in at least two classes of mental spatial transformation: imagined
transformations of one's egocentric perspective and imagined
transformations of the orientation of external objects. To the
extent that these are distinct systems, the efficiency of one
should vary independently of the other across individuals. Here we
present behavioral evidence that these two classes of computation
may indeed tap separate systems. Participants performed two
laboratory tasks that involved making spatial judgments about
pictures of human bodies: handedness judgments (left/right) about
individual bodies and parity judgments (same/mirror-image) about
pairs of bodies. We hypothesized that the first task would depend
primarily on egocentric perspective transformations, and the second
on object-based transformations. Consistent with earlier results,
there was a strong linear relationship between orientation and
response time for parity judgments but not for handedness
judgments. Performance on these tasks was compared to scores on
three tests of spatial ability: map-reading, perspective-taking,
and 3-D mental rotation. The first two were expected to tap
egocentric perspective transformation abilities, and the third was
expected to tap object-based transformation abilities. As
predicted, individuals' speed of handedness judgments correlated
better with their score on the map-reading test than the mental
rotation test. Conversely, speed of parity judgments correlated
better with their score on the mental rotation test than the
map-reading test.
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