Selective mechanisms in visual perception

The notion of perceptual tuning is investigated by presenting alternatives either before, after, or both before and after a tachistoscopic stimulus. Study 1 (N = 12) showed that identification accuracy is best with alternatives both before and after the stimulus, poorest with alternatives after the stimulus, and intermediate with alternatives only before the stimulus. Study 2 (N = 3) indicated that performance with alternatives both before and after the stimulus varies according to where S is permitted to fixate prior to each exposure. The possibility of a central tuning mechanism was not strongly supported.