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Abstract:
The perception and organization of local and global aspects
of form have been widely studied using hierarchical stimuli
consisting of a large global element made from smaller local
elements. The interaction of local and global form has been
examined by comparing performance using consistent stimuli (large F
made from smaller F's) to performance using inconsistent stimuli
(large F made from smaller E's). Most commonly, these studies have
reported a global advantage (quicker and more accurate responses to
the global level) as well as a global interference (slower and less
accurate responses to inconsistent stimuli at the local level).
This is known as global precedence. Only rarely has the opposite
pattern been reported and in these cases, with massive left
hemisphere damage, the evidence is relatively weak. We present JD,
a case of visual agnosia due to a degenerative disorder, whose
naming errors are primarily visual in nature (for example, she
names a line drawing of a mountain as a pile of string beans). We
presented JD with a variety of hierarchical letter stimuli to name.
While a small global-to-local interference (61 msec) indicates some
global processing ability, an overwhelming local advantage (2
seconds) and a massive local interference effect (4.45 seconds)
reveals strong evidence for local precedence. We discuss these
results as they relate to JD's visual agnosia, as well as to
theories of object recognition in general.
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