We (co-author Michael Lovas and I) have written quite a lot about first impressions. In particular the series of subconscious assessments that go on when we first meet someone. We know that the first thing that goes on is the "am I in danger?" assessment.
Every time a stranger looks at you, he or she makes a split-second determination as to whether you are friend or foe. Also among those split second assessments is an analysis of your attractiveness, likeability and credibility.
According to Princeton researcher and professor Alex Todorov, we are "hard wired" to quickly draw these inferences.
“The link between facial features and character may be tenuous at best, but that doesn’t stop our minds from sizing other people up at a glance. We decide very quickly whether a person possesses many of the traits we feel are important, such as likeability and competence, even though we have not exchanged a single word with them. It appears that we are hard-wired to draw these inferences in a fast, unreflective way.”
For more on first impressions, and in particular what people are "reading" to make these assessments, check out our book Axis of Influence - How Credibility and Likeability Intersect to Drive Success.
For more on Alex Todorov, check out All Things Considered, June 9, 2005 - Scientists Search for Winning Look. Forget political polls. Scientists usually can tell whether political candidates will win or lose by testing voters’ reactions to the contestants’ faces. A study in the journal Science shows that voters chose the face that looks more “competent.”
Professor Todorov’s Princeton Website