Work being carried out by the Todorov Lab part of the Department of Psychology at Princeton University has found that first impressions really do make a lot of difference, in fact with practice is may even be possible to tell if someone is violent or can be trusted just by a first impression! Obviously, this is early days, but it sure means that we should be many people going around with big smiles on their faces for no apparent reason.
According to the details on the Todorov Lab website;
The primary focus of research in our lab is on the cognitive and neural mechanisms of person perception with a particular emphasis on the social dimensions of face perception. Research on face perception intersects a number of different research areas – social psychology, cognitive psychology, cognitive neuroscience, and neuropsychology – and the approach in our lab is multidisciplinary.
We use a variety of methods from behavioural and functional Magnetic Resonance Imaging (fMRI) experiments to eye tracking, and computer and statistical modelling. The span of our research ranges from the social consequences of rapid, initial person impressions to the basic neural mechanisms underlying such impressions.
Source [Geeks Are Sexy]