Figure 1. Experimental paradigm.
(a) Participants played a social exchange task based on the ultimatum game. There were two blocks: one ‘Controllable’ condition and one ‘Uncontrollable’ condition. Order of the conditions was counterbalanced across participants. Each block had 40 (fMRI sample) or 30 (online sample) trials. In each trial, participants needed to decide whether to accept or reject the split of $20 proposed by virtual members of a team. In the fMRI study, participants rated their emotions after their choice in 60% of the trials. Upon the completion of the game, participants rated their subjective beliefs about controllability for each block. (b) The schematic of the offers (the proposed participants’ portion of the split) generation under the Controllable condition. Under the Controllable condition, if participants accepted the offer at trial t, the next offer at trial t+1 decreased by d={0, 1, or 2} (1/3 chance each). If they rejected the offer, the next offer increased by d={0, 1, or 2} (1/3 chance for each option). Such contingency did not exist in the Uncontrollable condition where the offers were randomly drawn from a Gaussian distribution (μ=5, σ=1.2, rounded to the nearest integer, max=8, min=2) and participants’ behaviors had no influence on the future offers.
Figure 1—figure supplement 1. Emotion ratings.
