Fig. 1: The intervene-or-watch task and participants’ behavioral patterns.
a,b, Schema of the intervene-or-watch task for the punishment (a) and helping (b) scenarios. c,d, Time course of a trial for the punishment (c) and helping (d) scenarios. In each trial, participants first saw the outcome of a dictator game—out of 100 tokens how much the dictator (transgressor, cartoon figure in orange shirt) allocated to themselves and to the receiver (victim, blue shirt): 70 versus 30 (c) or 88 versus 12 (d). As a third party starting with 50 tokens, participants (white shirt) were provided with an intervention offer, such as spending 10 of their own tokens to reduce the transgressor’s payoff by 15 tokens (c) or spending 20 of their own tokens to increase the victim’s payoff by 60 tokens (d). The participants’ task was to decide whether to accept the intervention offer (press ‘yes’) or do nothing (press ‘no’). e–h, Main effects of scenario (e), transgressor–victim inequality (f), impact-to-cost ratio (g) and intervention cost (h) on the probability of accepting the intervention offer, P(yes). Each filled circle denotes one participant. The bottom, middle and top lines of the box plot respectively indicate the 25th, 50th (median) and 75th percentiles. The whiskers extend to the minima and maxima within 1.5 times the range between the 25th and 75th percentiles from the bottom and top bounds of the box plot. The black dot inside each box denotes the group mean. ***P < 0.001 for the difference between adjacent conditions from Bonferroni-corrected post hoc comparison (see statistical details in Supplementary Section 3). The line superimposed on the boxes denotes the prediction of the best-fitting model (that is, the seven-motive motive cocktail model, described later). i–l, Interaction effects on P(yes), including an inequality × cost × ratio three-way interaction (i) and two-way interactions of scenario × ratio (j), inequality × ratio (k) and cost × ratio (l). Each circle denotes the mean across participants (N = 157). Error bars denote s.e.m. As in e–h, the lines denote the predictions of the best-fitting model. Credit: a–d, head icon, X. Mai.
