Abstract
Adaptation aftereffects are striking examples of how perception depends on stimulus history. Here, I present evidence that suggests that perception also depends on the observer's interpretation of the previous stimuli (i.e. a subjective stimulus history). More specifically, I present results of some recent psychophysical experiments in which subjects had to perform a sequential discrimination task about the relative orientations of serially presented visual stimuli. The results indicate that subjects' decisions were strongly biased by their previous decisions in the task sequence in a way that is orthogonal to the influence of the actual stimulus sequence. These findings cannot be explained by any current model of perceptual adaptation. However, the data are well described with a probabilistic observer model that is constrained to remain self-consistent with regard to its interpretation of sensory evidence over time. I discuss the degree to which this novel observer model can account for other aspects of perceptual and cognitive behavior, and how it might help us to better understand the intricate computational principles underlying adaptive sensory processing in the brain.