Deficits in the control of the attentional focus in chronic schizophrenics

The ability to control the size of the attentional focus and thus to modulate processing efficiency was investigated using simple reaction times in central vision in 17 chronic schizophrenic patients and 17 normal control subjects. The size of the attentional focus was manipulated by varying the size of a central box (i.e., a pre-cue), where the imperative stimulus appeared. In accordance with previous studies, in normal controls reaction time increased with box size. In contrast, in schizophrenic patients reaction time did not depend on box size. That is, schizophrenic patients did not show the inverse relation between size of the box and speed of processing, which is observed in normal controls. These results suggest that a deficit in controlling the size of the attentional focus is a basic impairment in chronic schizophrenia. It was also found that schizophrenics are more susceptible than controls to paracontrast.