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Abstract:
Abstract: The visual experience of a patient with
simultanagnosia becomes captured by local detail to the exclusion
of all other aspects of the global scene. We tested one patient
with simultanagnosia in order to explore whether information about
the global scene is entirely lost and whether the capture by local
detail can be overcome by providing more global information through
a different intact sensory modality. In a first experiment, we
showed her hierarchical stimuli in which the local and global
levels are incongruent or congruent (Navon 1977). Although she was
never aware of the global letter she was faster to name the local
letters for the congruent condition compared to the incongruent
condition. In a second experiment, she correctly identified the
global form via proprioceptive input, when her finger was passively
moved to trace the global shape, provided her eyes were closed. She
performed significantly better compared to a purely visual task.
When the same proprioceptive information was combined with vision,
her local capture returned with performance dropping to half the
level of the eyes-closed condition. Our experiments suggest that
the dominance of the local scale is not due to a total inability to
process global information but rather to an attentional bias
towards salient local details.
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