It is well appreciated that facial expressions play a major role in non-verbal social communication among humans and other primates, because faces provide rapid access to information about the identity as well as the internal states and intentions of others.
In his song, Mona Lisa, Nat King Cole reflected on the motivations for Mona Lisa's "mystic smile" and new data by scientists in Switzerland suggests that both the social context of a person's facial expression and certain facets of the viewer's personality could affect how our brain interprets the social meaning of someone else's smile or frown.
In a new brain imaging study published in the open-access journal PLoS ONE, Pascal Vrticka and colleagues at the Swiss National Center for Affective Sciences hosted by the University of Geneva 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.