A team of researchers led by Reginald B. Adams, Jr., of Dartmouth College and Harvard University used functional magnetic resonance imaging (fMRI) to study how the amygdala (a section of the brain that detects potential threats, regulates emotions and directs emotional behavior) reacts to faces displaying fear and anger. They showed subjects pictures of people with both angry and fearful facial expressions, some of which had been altered to change the direction of their gazes. The team found that pictures of angry faces with averted stares generated more amygdala activity than angry faces looking straight at the subject did. In contrast, an image of a fearful expression with a direct look elicited stronger signals than a picture of a fearful person looking aside did.
The researchers propose that where an angry or fearful person is looking helps others determine where a potential threat may lie. An angry person looking directly at you, for instance, indicates that he may be dangerous to you, whereas a fearful person looking off to the side indicates that something else in the vicinity is threatening. The new study suggests that more ambiguous situations require more work on the part of the brain to determine the cause of someone else's facial expressions. Adams notes that "this finding highlights the need for including eye gaze direction in future research examining how emotion is processed and perceived."