A face you can trust?

How impostors like Clark Rockefeller capture our trust instantly - and why we're so eager to give it to them.

Human beings are social animals, and our first instinct is to trust others. Con men, of course, have long known this - their craft consists largely of playing on this predilection, and turning it to their advantage.

But recently, behavioral scientists have also begun to unravel the inner workings of trust. Their aim is to decode the subtle signals that we send out and pick up, the cues that, often without our knowledge, shape our sense of someone's reliability.

Researchers have discovered that surprisingly small factors - where we meet someone, whether their posture mimics ours, even the slope of their eyebrows or the thickness of their chin - can matter as much or more than what they say about themselves. We size up someone's trustworthiness within milliseconds of meeting them, and while we can revise our first impression, there are powerful psychological tendencies that often prevent us from doing so - tendencies that apply even more strongly if we've grown close.

"Trust is the baseline," says Susan Fiske, a social psychologist at Princeton University. "Trustworthiness is the very first thing that we decide about a person, and once we've decided, we do all kinds of elaborate gymnastics to believe in people."

According to researchers, the subtler aspects of body language or physiognomy are difficult, if not impossible, to manipulate. But what has become public about Gerhartsreiter's methods - his preppy clothes, penchant for approaching people at country clubs and society events, and modest hints at a storied lineage - matches up with a body of research that suggests just how powerful signals of common identity and status can be, and how they can override our better judgment.

And they illustrate how, though we live in an era of worry over faceless Internet predators and Web identity thieves, we can be at our most vulnerable face-to-face.

Why trust exists in the first place has been something of a puzzle for scholars of human behavior. Evolutionary biologists (and economists) have traditionally assumed that people are self-interested, concerned only with maximizing their own well-being and passing on their genes to succeeding generations. That model doesn't leave much room for trust - why would we assume that someone would act on our behalf rather than simply his own?

Yet human society would not function without trust. We loan things to friends, we take to the road assuming our fellow drivers are not suicidal, we get on airplanes piloted by people we've never seen before, and, when asked to sign something, we rarely read the fine print. If people stopped to double-check the background and references of everyone they had an interaction with, social life would slow to a standstill.