| Summary: | Attention is one of the most impaired cognitive functions in schizophrenia; however, the precise mechanisms underlying schizophrenia-related attention impairment are unclear. Progress in identifying these mechanisms has been hampered by using methods that are not designed to isolate specific cognitive processes. The purpose of the present dissertation was to investigate visual attention among patients with schizophrenia using the visual search paradigm — the dominant paradigm for studying attention in the cognitive sciences. Moreover, the current study used eye-tracking methodology to more finely examine the mechanisms underlying impaired visual search in this clinical population. This dissertation had three main objectives: (1) to investigate whether patients with schizophrenia have smaller and/or less dynamic visual spans, (2) to examine whether certain mechanisms guiding the visual selection of objects are impaired in schizophrenia, and (3) to determine the contribution of visual search performance to substitution test performance. Results indicated that patients’ visual spans are both smaller and less dynamic compared to healthy controls. On the other hand, selectivity for more informative distractors is intact in schizophrenia; however, impaired motion perception results in impaired target discrimination in the context of intact target selection. Results also indicated that visual search performance is a primary determinant of substitution test performance. Collectively, these data demonstrate, on one hand, an impairment among patients with schizophrenia in the distribution and flexible modulation of visual attention and, on the other hand, intact visual selective attention in the presence of strong bottom-up cues. The current data also demonstrate the important contribution of visual attention to a highly sensitive neuropsychological test and, by inference, to patients’ cognitive and real-world functioning.
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