Figure 2. Binary Dictator Game results.

(a) The reverse-inference result: selfish choices appear to be faster than pro-social choices, based on a paired t-test of the mean, across subjects, of median reaction times (RT). (b) The difference in median RT between pro-social and selfish choices as a function of the overall probability of choosing the selfish option. Each dot represents one subject and the dashed line is a regression line. We see that uncommon choices take more time than common choices, and that for subjects who choose each option roughly half of the time, the difference in median RT is close to 0. (c) RT versus utility difference, conditional on choice type. Utility difference is calculated as the difference in utility between the chosen and unchosen options, using an individually fit inequity-aversion model. After controlling for utility difference, there is no difference in RT between selfish (black) and pro-social (blue) choices. Bars represent s.e. across subjects (n=25).