Washington, Aug 6 : They say a person's face reveals a lot about his or her intentions and personality. Now, new data suggests that both the social context of a person's facial expression and certain facets of the viewer's personality could affect how the human brain interprets the social meaning of someone else's smile or frown.
In the brain imaging study, which was published in the open-access journal PLoS ONE, Pascal Vrticka and colleagues at the Swiss National Center for Affective Sciences found that visually identical facial expressions can produce different patterns of responses in emotional brain areas when context changes their social meanings, and that these patterns of social sensitivity are strongly modulated by individual attachment style (i.e. how a person emotionally perceives and responds to others during social interactions, thought to be either secure, anxious or avoidant).
In this study, the specific brain substrates underlying these individual differences in reaction to emotional stimuli are identified for the first time.
Vrticka and colleagues manipulated the social significance of facial expressions by presenting them in different contexts while participants performed a pseudo-competitive game with virtual partners in the functional magnetic resonance imaging (fMRI) scanner.
The virtual partners could either be from allied or opponent teams and would display either a smiling or an angry expression in response to the success (or failure) of the participant.
A smile could thus be perceived either as praising an accomplishment or mocking a failure, and a frown either as a sign of reproach or frustration.
When the virtual partners were seen as allies (i.e. smiling in response to the success of the participant or looking angry when the participant failed), happy faces activated the ventral striatum and ventral tegmental area (areas of the brain associated with reward processing), but this response was much weaker in participants with an avoidant attachment style.
Angry faces, on the other hand, increased the activation of the amygdala (an area of the brain implicated in fear and arousal), especially in participants with an anxious attachment style.
These activation patterns were very specific, because no response in reward circuits or amygdala was found for facial expressions of virtual partners seen as opponents.
Instead, opponent's expressions led to increased activity in brain regions associated with theory of mind and alertness (superior temporal sulcus and anterior cingulate gyrus).
Vrticka and colleagues suggest that these data may ultimately help define appropriate intervention strategies in clinical disorders of attachment and social functioning, including social anxiety, social phobias and autism.