Drake Bennett of the Boston Globe wrote an article on the various ways con men gain their marks' trust, including body language, verbal language, and facial expressions.
When deciding who to trust, the research suggests, people use shortcuts. For example, they look at faces. According to recent work by Nikolaas Oosterhof and Alexander Todorov of Princeton's psychology department, we form our first opinions of someone's trustworthiness through a quick physiognomic snapshot. By studying people's reactions to a range of artificially-generated faces, Oosterhof and Todorov were able to identify a set of features that seemed to engender trust. Working from those findings, they were able to create a continuum: faces with high inner eyebrows and pronounced cheekbones struck people as trustworthy, faces with low inner eyebrows and shallow cheekbones untrustworthy.Judging trustworthiness in the face (via Mind Hacks)
In a paper published in June, they suggested that our unconscious bias is a byproduct of more adaptive instincts: the features that make a face strike us as trustworthy, if exaggerated, make a face look happy - with arching inner eyebrows and upturned mouths - and an exaggerated "untrustworthy" face looks angry - with a furrowed brow and frown. In this argument, people with "trustworthy" faces simply have, by the luck of the genetic draw, faces that look a little more cheerful to us.
Just as in other cognitive shorthands, we make these judgments quickly and unconsciously - and as a result, Oosterhof and Todorov point out, we can severely and immediately misjudge people. In reality, of course, cheekbone shape and eyebrow arc have no relationship with honesty.