Differential neural responses to faces physically similar to the self as a function of their valence.

Behavioral studies show that people self-enhance across a number of domains, including self-face recognition. We used functional magnetic resonance imaging (fMRI) to investigate whether response to physical similarity to the self would differ depending on whether the self-face was morphed with a positive (trustworthy) or negative (untrustworthy) novel face. Participants were presented with morphs of their faces (20%, 40%, 50%, 60%, and 80% self) and asked to decide whether the morph looked like them or the other face. Participants were more likely to identify the trustworthy than the untrustworthy morphs as looking like the self. Moreover, there were large differences in brain activation to trustworthy and untrustworthy morphs. As similarity of the untrustworthy morphs to the self decreased, the response in a number of regions, including bilateral posterior superior temporal sulcus/inferior parietal lobule, right inferior frontal gyrus, and bilateral middle/inferior temporal gyrus, increased. In contrast, there was little evidence for changes in activation as a function of the similarity to trustworthy faces. That is, these regions seemed to differentiate between the self and untrustworthy faces to a much greater extent than between the self and trustworthy faces, despite the fact that the task did not demand evaluation of the faces. The findings suggest that comparing the self to others who are viewed as positive versus negative triggers different psychological processes.