The case against full probability distributions in perceptual decision making

Abstract

How are perceptual decisions made? The answer to this seemingly simple question necessitates that we specify the nature of perceptual representations on which decisions are based. Recent work has taken for granted that the representation at the decision stage consists of a full probability distribution over all possible stimuli. However, to date, no empirical evidence has supported this assumption. Here I present five possible perceptual representation schemes that allow the extraction of different levels of sensory uncertainty. I review the empirical evidence from both continuous and discrete judgments and show that, at present, only the most primitive scheme based on a single point estimate can be rejected. In other words, at least four different representational schemes are consistent with the available data and therefore full probability distributions cannot be assumed. There is an urgent need for empirical research to adjudicate between these theoretical possibilities.