Certain personality traits are linked to a tendency toward exceedingly selfish behaviors. There may be a huge gap between the selfishness of a narcissist and that of a psychopath, but current research shows that all negative personality traits share the same dark core.

Egoism, Machiavellianism, moral disengagement, narcissism, psychological entitlement, psychopathy, sadism, self-interest, and spitefulness are all negative personality traits recognized in psychology.

Some of them, such as sadism, rely on other people's pain and discomfort for personal satisfaction.

Others, such as egoism, mean simply that a person is likely to place their own advantage first and foremost.

Despite the fact that each of these negative personality traits is characterized by excessive self-absorption and other similar inclinations to different degrees, they all stem from the same dark core, sharing the same psychological basis.

So argue researchers from the University of Copenhagen in Denmark, Ulm University, and the University of Koblenz-Landau—both in Germany.

These researchers have decided to call this dark core from which all negative traits are born the "dark factor of personality," or the "D-factor," for short.

The investigators' study, the results of which they report in the journal Psychological Review, involved surveying over 2,500 participants who answered questions about their behavioral and decision-making tendencies.

One negative factor to rule them all

In three online surveys, the researchers asked participants to what extent they agreed or disagreed with telling statements, including: "It is hard to get ahead without cutting corners here and there," and "It is sometimes worth a little suffering on my part to see others receive the punishment they deserve."

The participants also reported whether they had a tendency toward aggressive behaviors and impulsive decisions. Moreover, the researchers also assessed the respondents' selfishness and how likely they were to engage in unethical actions.

This information was then mapped onto the nine negative personality traits named before. After analyzing all the information they had gathered, the investigators concluded that all of those negative personality traits stemmed from the same dark tendencies.

Albeit to different extents, the researchers explain, the nine negative personality traits are all based on a rooted tendency to prioritize one's own well-being, pleasure, or success over those of others, even if it means others will have to suffer for it.

"[T]he dark aspects of human personality [...] have a common denominator," explains study author Professor Ingo Zettler. This, he adds, suggests that "one can say that they are all an expression of the same dispositional tendency."

"For example," says Professor Zettler, "in a given person, the D-factor can mostly manifest itself as narcissism, psychopathy, or one of the other dark traits, or a combination of these."

Not only do people with this "dark personality factor" seek their own advantage over the good of others, but they also come up with reasons why it is fine for them to disregard how their actions may affect other people.

'A useful tool'

The existence of a "D-factor" across a spectrum of negative traits also suggests something else—namely that if a person has one of these traits, they are likely to also have other, related ones.

"[W]ith our mapping of the common denominator of the various dark personality traits, one can simply ascertain that the person has a high D-factor," notes Professor Zettler.

"This is because the D-factor indicates how likely a person is to engage in behavior associated with one or more of these dark traits," he adds.

"In practice, this means that an individual who exhibits a particular malevolent behavior (such as likes to humiliate others) will have a higher likelihood to engage in other malevolent activities, too (such as cheating, lying, or stealing)," the investigator also observes.

Still, the researchers observe that the new framework they developed in the current study could help therapists and other specialists to better understand negative personality traits and thus to come up with better strategies to address them.

"We see [the D-factor], for example, in cases of extreme violence, or rule-breaking, lying, and deception in the corporate or public sectors. Here, knowledge about a person's D-factor may be a useful tool, for example to assess the likelihood that the person will reoffend or engage in more harmful behavior."

–Professor Ingo Zettler