Prior distributions.

Each panel shows the (unnormalized) probability density for a ‘prior’ distribution of targets, grouped by experimental session, with eight different priors per session. Within each session, priors are numbered in order of increasing differential entropy (i.e. increasing variance for Gaussian distributions). During the experiment, priors had a random location (mean drawn uniformly) and asymmetrical priors had probability 1/2 of being ‘flipped’. Target positions are shown in standardized screen units (from to ). a: Gaussian priors. These priors were used for the training session, common to all subjects, and in the Gaussian test session. Standard deviations cover the range to screen units in equal increments. b: Unimodal priors. All unimodal priors have fixed SD screen units but different skewness and kurtosis (see Methods for details). c: Bimodal priors. All priors in the bimodal session have fixed SD screen units but different relative weights and separation between the peaks (see Methods).