Behavioral analyses.

<p><i>a</i>. Reaction time on the image identification task decreases as the ‘ground-truth’ probability – the probabilities generated by the task program, and uninstructed to the participant – of that image appearing, conditional on the previous image increases. Here, for each participant, RTs were first corrected for their mean and a number of nuisance effects, estimated using a linear regression containing only these effects as explanatory variables. <i>b</i>. Across subjects, the fitted learning rate values that best explain behavior. For reaction times, the best-fitting model contained two learning rates (one ‘slow’, the other ‘fast’), whose estimates were combined linearly according to a fitted weighting parameter. For choice behavior, the best-fitting model contained one learning rate, statistically indistinguishable from the slow rate fit to reaction times, but significantly different from the fast.