High-level adaptation aftereffects for novel objects: the role of pre-existing representations.

Recent perceptual experience can strongly influence the way in which ambiguous stimuli are interpreted and categorized. A well known example is the phenomenon of adaptation aftereffects that occurs when prolonged exposure to a clear, prototypical image induce a repulsive bias in the perception of a subsequently presented ambiguous stimulus. When an ambiguous image is used as adapter, however, a facilitatory, attractive effect can be observed (priming effect). In this study, the role of a pre-existing representation in the induction of the perceptual effect was investigated, with the use of novel, unfamiliar objects (Greebles). The results of two experiments indicate that a pre-existing representation is necessary for aftereffects to be observed, but only when the contribution of low-level adaptation is controlled for. Increased familiarity with the stimuli is able to restore the repulsive effect, as indicated by a third experiment. The priming effect found for ambiguous adapters, on the other hand, seems not to be influenced by a previously stored memory representation.