Abstract
Making a categorical judgment can systematically bias our subsequent perception of the world. We show that these biases are well explained by a self-consistent Bayesian observer whose perceptual inference process is causally conditioned on the preceding choice. We quantitatively validated the model and its key assumptions with a targeted set of three psychophysical experiments, focusing on a task sequence where subjects first had to make a categorical orientation judgment before estimating the actual orientation of a visual stimulus. Subjects exhibited a high degree of consistency between categorical judgment and estimate, which is difficult to reconcile with alternative models in the face of late, memory related noise. The observed bias patterns resemble the well-known changes in subjective preferences associated with cognitive dissonance, which suggests that the brain's inference processes may be governed by a universal self-consistency constraint that avoids entertaining 'dissonant' interpretations of the evidence.
Highlights
We make thousands of decisions every day based on sensory information - where to walk, who to greet, and what to eat
The first goal was to obtain a quantitative characterization of how the perceptual inference process is affected by a preceding, categorical judgment (Figure 1a)
We have shown that in a discrimination-estimation task sequence, the estimated value of a stimulus variable is systematically biased by the preceding discrimination judgment about that variable
Summary
We make thousands of decisions every day based on sensory information - where to walk, who to greet, and what to eat. Helmholtz has described the perceptual decision process as a form of statistical inference (Helmholtz, 1867; Westheimer, 2008), referring to the fact that sensory information is inherently ambiguous and noisy (Kersten et al, 2004; Rust and Stocker, 2010). One common conclusion of this large body of work is that humans typically act like rational decision-makers that trade prior expectations about the world against uncertainty in the sensory evidence in order to optimize perceptual accuracy. Most of these previous studies considered perceptual judgments as independent, isolated events, which starkly contrasts with real-world situations where perceptual judgments are often embedded in a sequence of other judgments involving the same sensory evidence.
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