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Abstract:
Humans are extraordinarily good at detecting statistical
regularities in the environment. The question of whether the
mechanisms underlying the attentional deficit exhibited by patients
with hemispatial neglect due to right parietal lobe damage can
calibrate to regularities in the neglected field was examined. In a
visual search task on which the target appeared on one side of the
screen (left/right) on 80% of the trials and 20% on the other side,
control participants quickly adapted the strategy of orienting
attention to the side on which the target was more likely to
appear. Reaction time (RT) to targets in the more probable half
decreased throughout the experiment whereas RT to the other side
increased. Participants were asked to identify a number in the
center of the screen at the beginning of each trial as a measure of
central fixation, but were otherwise free to move their eyes during
target search. The results of neglect patients were qualitatively
similar to those of control participants: the difference in RT to
targets on the left and right side of the screen decreased
throughout the experiment until they were indistinguishable. These
data suggest that the patients with hemispatial neglect are
sensitive to statistical regularities of objects in an unspecified
location within the neglected field. Moreover, they are capable of
exploiting these short-term probability effects to enhance task
performance without explicit instructions to do so.
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