How recent experience affects the perception of ambiguous objects

Sensory information from the external world is inherently ambiguous, necessitating prior experience as a constraint on perception. Recent experience with clear, prototypical stimuli may, however, induce complex effects on the subsequent perception of ambiguous ones, ranging from attraction (priming) to repulsion (adaptation aftereffects). In the present study, we ask what determines the direction and magnitude of the effects in the case of images of naturalistic (complex) objects, which are putatively analyzed in advanced visual cortices and under the influence of multimodal semantic memories. We find a basic crossover from adaptation aftereffects to priming effects as the delay lengthens between experiencing a prototype and seeing the ambiguous stimulus. Adaptation aftereffects appear as a shift in the perceptual boundary between distinct object images, which vanishes with time, unmasking an overall and temporally sustained priming bias. A similar attractive bias occurs when the original adapter is substituted by an ambiguous image.