How Do Expectations Change Behavior? Investigating the Contributions at Encoding Versus Decision-Making

Expectations about the environment play a large role in shaping behavior, but how does this occur? Do expectations change the way we perceive the world, or just our decisions based on unbiased perceptions? We investigated the relative contributions of priors to these 2 stages by manipulating when information about expected color was provided. We compared cases where the prior could affect encoding into perceptual/working memory representations (e.g., when provided prestimulus) against cases where it could not (e.g., when given at response after a delay). Although priors had a minor influence on encoding, the bulk of the effects were at decision-making. Furthermore, these effects appeared to be distinct. The effect on decision-making was Bayesian-like, with priors inducing bias while improving precision. In contrast, the same priors at encoding improved precision without causing changes in bias.