Figure 2 - Altruism is predicted by pSTC activation.

In each of our two fMRI experiments (E1 and E2), we examined the relation between the subjects' self-reported altruism and the magnitude of activation in pSTC. (a,b) E1. (c,d) E2. All data are drawn from pSTC regions of interest whose centroids are reported in Figure 1. Low-altruism subjects showed no difference in pSTC activation between Watching trials (gray bars, indicated by eye) and Playing trials (white bars, indicated by hand) in either E1 (a) or in E2 (c). All bars indicate group mean s.e.m. High-altruism subjects exhibited significantly greater pSTC activation for Watching than for Playing trials. Across subjects, there was a significant correlation between altruism scores and pSTC activation for both E1 (b) and E2 (d). Y-axes for a and b represent the difference in percent blood-oxygenation signal between Watching and Playing, and y-axes in c and d represent the difference in the Watching and Playing parameter estimates, which provides an estimate of relative blood-oxygenation signal, normalized to arbitrary units.