Fig. 1. Schematic of the experimental paradigms in mice and monkeys and basic behavioral results.

a, b Timeline of a single trial during experiments in mice (a) and monkeys (b). To initiate a trial, mice received an olfactory go cue (or no-go cue in 5% of trials) (a), and monkeys fixated on a central point (b). Next, animals chose (via licks for mice and saccades for monkeys) between two options (left or right tubes for mice and circle or square for monkeys) and then received a reward (drop of water and juice for mice and monkeys, respectively) probabilistically based on their choice. c, d Average choice and reward using a sliding window with a length of 10 for a representative session in mice (c) and five superblocks of a representative session in monkeys (d). Mean selection of 1 and −1 correspond to 100% selection of or 100% reward on the right and left in mice (square and circle stimuli in monkeys), respectively, and mean selection of 0 corresponds to equal selection or reward on the two choice options. Vertical gray dashed lines indicate trials where reward probabilities reversed. Vertical gray solid lines indicate divisions between superblocks in the monkey experiment. e, f Average relative choice and reward fractions around block switches using a non-causal smoothing kernel with a length of three separately for all blocks with a given reward schedule in mice (e) and monkeys (f). The better (or worse) option is the better (or worse) option prior to the block switch. Trial zero is the first trial with the reversed reward probabilities. Average choice fractions for the better option (better side or stimulus) are lower than average reward fractions for that option throughout the block for both mice and monkeys, corresponding to undermatching behavior.