Economics and sociology have long recognized that individuals value the outcomes of their actions depending on the outcome of their peers. They have also indicated a reason for this attention: Individuals consider outcomes as signals of some hidden quality; for example, conspicuous consumption is a costly signal of an otherwise unobservable variable, like wealth, or skill in business. This insight has been used to explain a wide range of phenomena, from animal behavior (Zahavi) to investment in education (Spence). Here we show that the brain discriminates monetary outcomes depending on whether they signal skill or luck when compared to those of others: Activation in the medial orbitofrontal cortex (OFC) is stronger when outcomes signal better skill of the individual. Moreover, individual activation differences in the same medial OFC region predict differences in behavior: when subjects have the opportunity of subtracting money from others, they do so more the larger their medial OFC activation due to relative skill but not luck. Ventral striatum also codes relative outcomes, but independently of skill or luck. These data suggest that medial OFC specifically codes personal responsibility on outcomes, which could form the neuronal basis of social regret.