Implicit learning modulates selective attention at sensory levels of perceptual processing.

Electrophysiological evidence suggests that attention can be modulated as early as 100 msec after stimulus presentation. However, it is not clear whether these changes are based primarily on stimulus properties such as perceptual load (i.e., the level of perceptual difficulty), or other properties, such as general attentional set or learned expectations concerning perceptual load. Using event-related potentials, this study examined how implicit learning of perceptual load conditions modulates selective attention at sensory levels of perceptual analysis. The results show significant differences in P1 amplitude recorded over occipital areas of the brain as a function of learned expectations of perceptual load, only when perceptual load could be reliably predicted by the preceding stimuli. Moreover, differences in processing were found when both low and high perceptual load conditions could be predicted. These findings suggest that implicit learning modulates the allocation of attention at early stages of perceptual processing.