Perceptual learning of global pattern motion occurs on the basis of local motion

Enhancement in perceptual learning of a visual stimulus can often be explained either by learning of integrated visual information that is processed in higher visual areas or by learning of component information that is processed in lower visual areas. It is not clear on which visual information perceptual learning is predominantly based. We examined whether perceptual learning of global pattern motion occurs on the basis of local or global motion as a result of performance improvement in detecting contraction (or expansion) in a display in which contracting (or expanding) dots slightly outnumbers expanding (or contracting) dots. We measured the degree of transfer of the learning effect by presenting test stimuli spatially shifted so that the region of the test stimuli partially overlapped the trained region. The results showed that the degree of transfer was entirely dependent on how similar local motion directions in the test stimuli are to those in the trained stimulus in the overlapping area, irrespective of whether a test stimulus contained the same global motion direction as the trained or not. These results indicate that perceptual learning at least in the present setting occurs on the basis of local motion signals.