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.