Fig. 1: Task design and difficulty manipulation.

a Trial structure during free play. The panels show 3 example free-choice trials consisting of 3 steps each. Each trial began with a choice among 4 "monster families" depicted as visual icons (1). This was followed by the presentation of a randomly drawn individual from that family and a prompt to guess which of two possible foods the individual liked to eat (2). After guessing (2), the participant received immediate feedback (3) and the next trial began. Participants were free to repeat the previously sampled activity (e.g., trial t + 2 in this figure) or switch to any other monster family (e.g., trial t + 1) as they wished. b Performance during the forced-choice familiarization stage. Each box plot shows the %correct (PC) during the 15 familiarization trials in which participants had to play each activity for the IG (blue; N = 186) and EG (red; N = 196) groups. Horizontal bars inside boxes show the median values across all participants in a group; box boundaries show the 1st and the 3rd quartiles; whiskers show sample minima and maxima. Image credits (a): monster character designs by macrovector/Freepik; food-item designs by brgfx/Freepik. Source data for b are provided as a Source Data file.