Existing research from Princeton University on how adults process trustworthiness helped LaBar's team pinpoint the facial features that prompted feelings of mistrust in these participants. According to the research, faces with downward-turned mouths and furrowed eyebrows are among the most untrustworthy. In contrast, faces with U-shaped mouths and wide-set eyes rank among the most trustworthy.
Based on the fMRI results, the components of the limbic system known as the amygdala (which evaluates negative emotions) and insula (which plays a role in gut-level decision making) were the most active for the faces participants rated as untrustworthy. Among all ages, the right amygdala showed high levels of activity when presented with an untrustworthy face. Other spots within the amygdala and insula also demonstrated increased activity in these instances, peaking among the 13- to 15-year-old participants.
"These heightened responses for untrustworthiness suggest that during this time, girls this age are particularly sensitive to the facial features they feel are untrustworthy," LaBar said. "We don't know why. Maybe it's a post-pubertal hormone change that brings on the heightened response, or maybe they're more motivated to scan for social threats during this period."
The fMRI results also revealed that during mid-adolescence, the amygdala, while active, shows reduced connectivity with other parts of the brain involved in facial processing, including the insula and temporal lobe. Rather than these areas working in sync, LaBar said, participants this age experienced enhanced limbic system (emotional and behavioral) resp
|Contact: Karl Bates|