Deficits at the earliest stages of information processing are among the most consistent abnormalities found in schizophrenics. To better understand the deficit, the present study indirectly evaluated the functional status of two visual channels, transient and sustained, which have been implicated in early information processing. A forced-choice, two-pulse detection task was used to determine the duration that subjects required to detect a blank interval (ISI) separating a two pulse grating vs. a single pulse grating. Threshold ISI was used as the index of visible persistence. Four groups of subjects participated in the study: schizophrenics, schizoaffectives, major depressives, and normal controls. The results of the ANOVA showed a significant main effect for diagnosis, position, and spatial frequency, as well as a significant effect for diagnosis x position and diagnosis x spatial frequency. The results are discussed in terms of the differential response and retinal distribution of each channel.