The pre-registration report uploaded here provides: - the description of hypotheses, computational models, experimental methods, analyses and results from fMRI Study 1 - the pre-registration of methods and hypotheses for fMRI Study 2 The data uploaded in aggregate_data folder consists of aggregated (post-analysis) behavioral and fMRI (region of interest) data used to plot most figures of the manuscript. The data uploaded in raw_behavioral_data folder consists of the raw behavioral data files obtained for each participant at the end of the task, separately for Study 1 and Study 2. Each row is a trial; column description is as follows: - column 1: index (trial number starting from 0) - column 2: trial number per run - column 3: run order - column 4: run ID - column 5: trial type (1: observe, 2: play) - column 6: goal token (1: green, 2: red, 3: blue) - column 7: volatility condition (1: stable, 2: volatile) - column 8: uncertainty condition (1: low, 2: high) - column 9: unavailable action (1: left, 2: middle, 3: right) - column 10: correct action (1: left, 2: middle, 3: right), also partner's choice on observe trials - column 11: best action (1: left, 2: middle, 3: right) - column 12: vertical order of colors within slot machine (1:G/R/B, 2: R/B/G, 3: B/G/R) - column 13: horizontal order of slot machines (1: G-R-B, 2: R-B-G, 3: B-G-R) - column 14: onset of trial type ('observe' or 'play' displayed on screen) - column 15: onset of slot machine - column 16: onset of first fixation (observe trials only) - column 17: onset of choice screen (play trials only) - column 18: choice (play trials only; 1: left, 2: middle, 3: right) - column 19: reaction time in seconds (play trials only) - column 20: whether choice is correct (1) or not (0) - column 21: onset of choice response (play trials only) - column 22: onset of choice feedback (play trials only) - column 23: onset of video displaying partner's choice (observe trials only) - column 24: ID of video being shown - column 25: onset of second fixation - column 26-28: probability of getting the green, red or blue token given choice - column 29: probability of getting the goal token given choice - column 30: random number generated to determine which token is obtained - column 31: whether token shown is the goal (1) or not (0) - column 32: token shown (1: green, 2: red, 3: blue) - column 33: onset of token presentation - column 34: outcome in cents - column 35: onset of ITI fixation - column 36: missed trial index - column 37: onset of missed trial message