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Abstract:
Abstract: Numerous studies have reported semantic memory
impairments in patients with schizophrenia. We investigated whether
semantic boundaries of categories are intact in these patients,
compared to controls. Experiment 1: We examined the integrity of
semantic memory in a reaction time task in which words were
verified as members or non-members of a category. The words varied
in their relationship to the category (e.g., "robin", "turkey",
"penguin", range from typical to less typical). Chen et al. (1994)
found that schizophrenic patients were slowest to respond to words
semantically associated but outside the category (e.g., "airplane"
to cue "bird"), thus concluding that category boundaries had
shifted in patients. However, we found both groups responded
slowest to "borderline" items (e.g., "penguin" to cue "bird").
Experiment 2: We used visual objects that were morphed (e.g.,
"pencil" to "toothbrush"), and manipulated the level of semantic
relatedness of object pairs. Participants decided when items were
no longer that item. The groups were equivalent in their
sensitivity to detect category boundaries, and in perceptual
identification of stimuli. These findings suggest, despite wide
ranging cognitive deficits in schizophrenic patients, semantic
boundaries of categories are intact. This contrasts with our
findings that spreading semantic activation among entities is
abnormal, thus suggesting impairments in semantics are restricted
and specific. Reference: Chen, E.Y.H., Wilkins, A.J., McKenna, P.J.
(1994). Semantic memory is both impaired and anomalous in
schizophrenia. Psychological Medicine, 24, 193-202.
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