Fig. 1.

Visual display of events presented in the mini Ultimatum Game. Trials started with a jittered fixation screen lasting 550–4950 ms. The left panel in the decision screen displayed the name of the proposer in red (here ‘proposer’) and the name of the responder (here ‘responder’). Two offers each containing red and blue coins indicate the share for the proposer (red coins) and the responder (blue coins), the offer made by the proposer was encircled in yellow (here 8/2). The responder was given a maximum response time of 5000 ms to select Yes or No to accept or reject the offer. If they failed to respond within 5000 ms, a screen displaying ‘Too late!’ was presented for 1000 ms. Upon response, the feedback screen displayed the given response (here ‘No’) until 6000 ms after the start of the trial. Trials were randomized and presented with a jittered interstimulus interval (mean = 1530 s, min = 550 ms, max = 4950 ms; optimized with OptSeq2, (surfer.nmr.mgh.harvard.edu/optseq/). Both the ‘fair alternative’ and ‘no alternative’ condition are displayed.