Visual search in schizophrenia: latent inhibition and novel pop-out effects

A visual search task was used to assess attentional function in a mixed gro up of schizophrenic patients and in normal controls. Subjects identified pr esence or absence of a unique shape presented with homogeneous distracters. Response time (RT) was examined as a function of prior experience with tar get, distracter, or both. On each trial, targets and/or distracters were ei ther novel or familiar. Schizophrenic patients were slower than controls in all conditions. In the test phase, three target/distractor conditions were examined (PE - target and distracters preexposed but reversed; NPE - targe t novel and distracters pre-exposed; NOV - novel target and distracters). A s predicted, normal controls, but not schizophrenics, showed latent inhibit ion (LI: PE minus NPE). The latter finding was due to the absence of normal LI in female patients. A novel pop-out effect (NOV minus NPE) was obtained which did not interact with any of the other variables. The results sugges t that the LI effect is indeed related to the processing of irrelevant stim uli, and that, at least female schizophrenic patients process such stimuli differently from controls. Past inconsistencies in the LI-schizophrenia lit erature may be the result of disproportionate gender compositions in patien t and control groups. (C) 2000 Elsevier Science B.V. All rights reserved.