It can be difficult to articulate what exactly it is about one's roommate, or coworker, or best friend's boyfriend that makes them so unpleasant. Luckily, pinning down definitions for the "dark traits" that can compromise a person's moral character is its own area of research. A recent study on the subject suggests that spotting ethically bankrupt people may not be as complicated as we once thought. The findings suggest that someone who exhibits one dark trait is likely to have more of them.

For a series of studies, the results of which were published in the journal Psychological Review, psychologists from the University of Copenhagen and the University of Koblenz-Landau surveyed 2500 participants. They asked them how much they agreed with statements such as “It is sometimes worth a little suffering on my part to see others receive the punishment they deserve,” and “I know that I am special because everyone keeps telling me so.” These questions were meant to gauge the degree to which participants showed these nine personality traits with negative connotations:

  • Egoism: an excessive preoccupation with one's own advantage at the expense of others and the community

  • Machiavellianism: a manipulative, callous attitude and a belief that the ends justify the means

  • Moral disengagement: cognitive processing style that allows behaving unethically without feeling distress

  • Narcissism: excessive self-absorption, a sense of superiority, and an extreme need for attention from others

  • Psychological entitlement: a recurring belief that one is better than others and deserves better treatment

  • Psychopathy: lack of empathy and self-control, combined with impulsive behavior

  • Sadism: a desire to inflict mental or physical harm on others for one's own pleasure or to benefit oneself

  • Self-interest: a desire to further and highlight one's own social and financial status

  • Spitefulness: destructiveness and willingness to cause harm to others, even if one harms oneself in the process

If subjects exhibited one of the tendencies on this list, it usually wasn't their only questionable trait. The researchers found that someone who lacks empathy also tends to be manipulative and egotistical, suggesting that a dark personality is more than the result of a specific combination of traits. Rather, the traits are all symptoms of what the study authors describe as "the D-factor." According to a release from the University of Copenhagen, all of these unsavory behaviors stem from "the general tendency to maximize one’s individual utility—disregarding, accepting, or malevolently provoking disutility for others—accompanied by beliefs that serve as justifications."

That means people who are obsessed with only serving themselves and who don't mind, or might even enjoy, putting others down exhibit the D-factor. Many universally unacceptable behaviors—like violence, lying, stealing, discrimination—can be sorted under this umbrella.

Psychologists may be able to use the research to further study the cause of and relationships between malevolent behaviors in the future. The results could also be useful to anyone who wants to know which type of people to avoid.