In a wonderful book, “The Invisible Gorilla”, the authors, Christopher Chabris and Daniel Simons, write on the “trait” of confidence.

“Psychologists use the term trait to describe a general characteristic of a person that influences his or her behavior in a wide variety of situations. In Anderson and Kilduff's study of group leadership, dominance was taken to be a trait-people scoring high on the researchers' dominance test were thought to assert control and assume power across a wide range of situations. Similarly, if you score high on a test of extraversion, you are probably more outgoing than the average person, and your tendency to approach and engage with other people will manifest itself more often than not.

Personality traits don't determine your behavior all the time-many other factors, especially ones particular to the situation you are in, have powerful influences as well. An extraverted person who knows nothing about Star Trek might be more shy at a science-fiction convention than an introvert who attends these events all the time. However, extraverted people tend toward more social engagement in the absence of other overriding situational factors. By default, they are more socially gregarious than are introverted people.

Confidence itself doesn't show up in most of the lists of traits compiled by psychologists. It isn't one of the so-called "big five" dimensions, which include neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness. Confidence is related to, but is not the same as dominance, and even dominance isn't typically measured in studies of personality. We think that differences among people in their tendency to express confidence are vitally important for understanding how we make decisions and influence one another. So do these differences exist? Is confidence a trait?

The “con” part of “con man,” “con artist,” and “con game” is short for confidence. The original “confidence man” was a grifter in the 1840s named William Thompson, who had the audacity to approach strangers on the streets of Manhattan and simply ask them to hand over their watches. Attempting this gambit required Thompson to somehow gain the confidence of his marks; amazingly, he was able to do this while explicitly asking them, "Have you confidence in me to trust me with your watch until tomorrow?"

The most inherently confident person in history might have been Frank Abagnale, who was portrayed by Leonardo DiCaprio in Steven Spielberg's movie Catch Me If You Can. Abagnale started early: While still a high school student, he successfully impersonated a high school teacher, and he conned his father out of $3,400. By the age of eighteen, pretending to be a Pan Am pilot, he had tricked the airline into letting him fly over one million miles as a "deadhead"-riding in unsold seats or as a guest in the cockpit. He expertly forged checks worth millions of dollars. When he was finally arrested in France, at the age of twenty-one, he was wanted in twelve countries. After being tried and serving time in France and Sweden, he was extradited to the United States, where he repeatedly escaped and eluded authorities, on one occasion by pretending to be an undercover investigator looking into allegations of poor conditions for prisoners. Eventually he was recaptured and convicted. As part of a deal with American prosecutors, he agreed to assist the FBI in future investigations of other frauds in exchange for early parole. The diversity, ease, and precociousness of his con games attest to his ability to display levels of confidence that people expect to see only in those who are telling the truth.

Some researchers wondered whether confidence is a stable trait, as the careers of Abagnale and Thompson suggest. They conducted a simple experiment to find out. Subjects were asked to answer a series of challenging true/false trivia questions, such as "the O.J. Simpson murder trial ended in 1993" (false-it ended in 1995), and to express their confidence in each answer as a percentage (between 50% and 100%). On this test, most people express considerable over-confidence: They get about 60 percent of the answers correct, but their average confidence is about 75 percent.

The critical element in the design of this experiment was the creation of two trivia tests that were equally difficult but included entirely different questions. Each subject first completed one of the tests, and then several weeks later, completed the other one. Remarkably, just by knowing how confident someone was on the first test, it was possible to predict how confident they would be on the second test. Of those people who scored in the top half on confidence in the first test they took, 90 percent scored in the top half on the second test. Yet confidence did not predict accuracy; the more confident people were no more accurate than the less confident people. Confidence also was unrelated to intelligence.

Other experiments have shown that confidence is a general trait: People who are highly confident of their skills in one domain, such as visual perception, also tend to be highly confident of their skills in other domains, such as memory. In short, confidence appears to be a consistent quality that varies from one person to the next, but has relatively little to do with one's underlying knowledge or mental ability. One thing that does appear to influence confidence is genes. According to a recent study by a group of economists in Sweden, identical twins are more similar to each other in how confident they are of their own abilities than are fraternal twins. Since identical twins have essentially the same genes, but fraternal twins are no more similar genetically than ordinary siblings, confidence must have at least some genetic basis. Your confidence isn't entirely determined by your genetic makeup, but it's not entirely independent of it. As it turns out, Frank Abagnale's father was also a con man; he lost the family home in a failed tax-fraud scheme.”