Psychologists study three "dark" personality traits. They call them the Dark Triad. The first is using other people for your own goals. The second is thinking you are very special. The third is not caring much about other people's feelings. These are not illnesses.

Everyone has a little of each trait, and most people are low or in the middle. People high in these traits may seem charming at first, but they often lose trust later.

In 2002, two Canadian psychologists, Delroy Paulhus and Kevin Williams, grouped three personality traits together and named them the Dark Triad. Machiavellianism is a tendency to manipulate others for personal gain. Narcissism is a strong sense of being special and a need for admiration.

Psychopathy involves low empathy and impulsive, thrill-seeking behavior. The three traits overlap, but they are not the same. Nor are they medical diagnoses. Everyone has them to some degree, and most people score low to medium.

Researchers later added a fourth trait, everyday sadism, which means enjoying others' suffering. In a 2014 study, people who enjoyed online "trolling" scored higher on sadism. These traits may help people at first, since narcissists often make good first impressions, but over time they tend to damage trust.

In 2002, Delroy Paulhus and Kevin Williams compared three personality traits that had been studied separately and labeled them the Dark Triad. Machiavellianism is a calculating willingness to exploit others. Narcissism combines grandiosity with a hunger for admiration. Psychopathy is marked by callousness, impulsivity and thrill-seeking. The three are moderately correlated but distinct, and they are dimensions present in everyone, not clinical diagnoses.

Later work added everyday sadism, the enjoyment of others' suffering, to form a "Dark Tetrad," and a 2014 study found that people who enjoyed online trolling scored higher on it. In 2018, Moshagen and colleagues proposed that all these traits share a common core, the D factor, which amounts to pursuing one's own benefit while disregarding the costs to others. Such traits can pay off at first.

A 2010 German study showed that narcissists tend to be liked on first meeting, partly because they look confident. A 2017 meta-analysis, however, linked the triad to low agreeableness and negative psychosocial outcomes. Most of this evidence comes from self-report questionnaires and is correlational, and some researchers argue that Machiavellianism and psychopathy are almost impossible to tell apart in practice. The scales were never designed for labeling individuals.