Further evidence for monocular determinants of perceived plaid direction.

This report adds to existing evidence that a monocular, feature-sensitive motion mechanism is involved in two-dimensional (2-D) motion processing, and also accounts for an earlier, unexplained result [Alais et al.(1994) Vision Research, 34, 1823-1834]. The central finding is that the perceived direction of a monocularly viewed type II plaid changes over a period of continuous exposure such that post-adaptation direction judgements exhibit more of the component-direction bias known to occur with these stimuli than pre-adaptation judgements. These adaptation effects are confined to the adapted eye: when the adapting stimulus is presented to one eye, pre- and post-adaptation direction judgements made with the other, non-adapted eye are identical. These results strongly suggest the involvement of a monocular motion mechanism in two-dimensional motion processing, in addition to the more commonly presumed binocular mechanisms.