Pupil dilation offers a time-window on prediction error

In the current study, we investigated whether the pupil’s response to decision outcome in the context of associative learning reflects a prediction error defined formally as information gain, while also exploring the time course of this prediction error signal. To do so, we adapted a simple model of trial-by-trial learning of stimulus probabilities based on information theory from previous literature. We analyzed two data sets in which participants performed perceptual decision-making tasks that required associative learning while pupil dilation was recorded. Our findings consistently showed that a significant proportion of variability in the post-feedback pupil response during decision-making can be explained by a formal quantification of information gain shortly after feedback presentation in both task contexts.