Fig. 1.

An illustration of the task sequence in a single trial for Player A (i.e. the EEG participant). Each trial contained two sessions: the priming phase (Figure 1A) and the card-guessing task phase (Figure 1B). First, after a presentation of a white cross (200 ms), participants in each of the two prime conditions viewed 10 priming stimuli on the screen for 1000 ms consisting either images of banknotes or tropical fish. Then, a fixation cross was presented for 500 ms on a black background. Subsequently, all participants were presented with two green squares (2.5 × 2.5°) representing two cards, which appeared on the left and right sides of the fixation cross. They were required to choose one of the two cards to give to Player B by pressing a corresponding key (‘F’ or ‘J’ key) with their left or right index finger, respectively. After making the choice, the chosen card was highlighted by a red border for 500 ms. After a variable interval of 600–800 ms, participants were informed whether Player B accepted or rejected their selection by displaying ‘Player B Accepts’ or ‘Player B Rejects’ on the screen for 1000 ms. Then, the outcome for Player B was displayed on the screen after a variable interval of 600–800 ms: ‘Player B + 10’ or ‘Player B − 10’ was shown for 1000 ms, with the ‘+’ suggesting the other player gained 10 Yuan and the ‘−’ indicating the advisee lost 10 Yuan. The inter-trial interval lasted for 1000 ms. The ERP data of the outcome evaluation stage were time-locked to the outcome for Player B (marked with a red square in the figure). ISI: inter-stimulus interval.