Figure 1

Study design. (a) The three phases of the Inequality Game (given in successive scanning runs). (b) Depiction of event frames of a single trial in the high power phase with their respective duration. Each time the participant is paired with one of the two other players, a screen is displayed that reads “Selection of participants”. Then, participants see a photograph of the other (fair or unfair) that is accompanied with the information that this player controls the columns in the high power phase (and the lines in the low power phase). This is followed by the display of the payoff matrix determining the distribution of gains for the two current players (“New Trial”), the decision screen for the person in high power (“Decision Lines”), the display of this decision (“Result Lines”), a display indicating that the other person is deciding (“Decision Columns”), and lastly the display of the other’s decision which serves at the final outcome display (“Final Result”). In the current example, the player with high power (here: Nicolas, in green) begins by selecting a line in the matrix, which is followed by the choice of the low power player (here: Jean, in blue) who selects a column. The intersection of their choice determines the final gain allocated to each player (here a competitive distribution is depicted in which Nicolas earns 8 CHF and Jean earns 1 CHF). Then, the player with high power can select one of four feedback messages for the other player.