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Abstract:
M.B., a 39 year old prosopagnosic with category-specific
agnosia for living objects was tested for her ability to 1) detect
configural and feature-based changes in schematic faces and
non-faces, 2) process at global and local attentional levels and 3)
verify the identity of living and non-living objects at different
levels of categorization. In the face task, normal controls showed
equivalent and relatively lower sensitivity to featural changes in
faces and non-faces. Their sensitivity to configural changes in
non-faces was of a similar magnitude. However, they were highly
sensitive to configural changes in faces. M.B. showed normal
sensitivity to featural changes in faces and non-faces. Notably,
the normal pattern of high sensitivity to configural changes in
faces was absent. She also showed impaired local processing of
Navon-type figures in a divided attention task. Finally, decisions
about whether superordinate, basic, or subordinate names matched
living and non-living objects showed a living advantage and faster
responses to basic than subordinate or superordinate names with
normal controls. M.B. showed a relatively normal pattern of
responses to levels of categorization. Interestingly, her
category-specific deficit was most profound for superordinate
decisions. M.B. has a visual impairment that manifests as a
configural face-processing problem that may be linked to abnormal
local attentional allocation. Her category-specific problems are
likely of a semantic nature.
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