Ethically, morally, and socially questionable behavior is part of everyday life and instances of ruthless, selfish, unscrupulous, or even downright evil behavior can easily be found across history and cultures. Psychologists use the umbrella term “dark traits” to subsume personality traits that are linked to these classes of behavior - most prominently, Machiavellianism, Narcissism, Psychopathy, and Sadism. Over the years, more and more allegedly distinct and increasingly narrow dark traits have been introduced, resulting in a plethora of constructs lacking theoretical integration.
In proposing D — the Dark Factor of Personality — we theoretically specify what all dark traits have in common, i.e., their common core. Our conceptualization of D provides a unifying, comprehensive theoretical framework for understanding dark personality. In analogy to the general (g) factor of intelligence, D represents the one basic general dispositional tendency of which specific dark traits arise as manifestations. For example, D may manifest itself in Narcissism and/or Psychopathy, but also in any other specific dark trait such as Amorality, Egoism, Greed, Machiavellianism, Psychopathy, Sadism, or Spitefulness, as well as in any combination thereof. Thus, instead of saying that an individual is an amoral, egoistic, narcissistic psychopath who selfishly acts according to her/his own interests and, in doing so, engages in sadistic and spiteful behaviors, one may just say that this individual displays high levels in D. D explains why dark traits are connected and thereby forms the theoretical basis for the emergence of dark personality in general.
For a very informative summary, take a look at Scientific American.
In substantive terms, D is defined as:
The general tendency to maximize one's individual utility — disregarding, accepting, or malevolently provoking disutility for others —, accompanied by beliefs that serve as justifications.
Correspondingly, D is understood as a basic, general dispositional tendency, of which dark traits arise as specific manifestations. Thereby, all communalities between various dark traits can be traced back to D, so that D represents the common core of dark traits. In terms of content, individuals with high levels in D will generally aim to maximize their individual utility at the expense of the utility of others. Utility is understood in terms of the extent of goal achievement, which includes different (more or less) visible gains such as excitement, joy, money, pleasure, power, status, and psychological need fulfillment in general. Thus, individuals high in D will pursue behaviors that unilaterally benefit themselves at the cost of others and, in the extreme, will even derive immediate utility for themselves (e.g., pleasure) from disutility inflicted on other people (e.g., pain). Vice versa, individuals high in D will generally not be motivated to promote other’s utility (e.g., helping someone) and will not derive utility from other’s utility as such (e.g., being happy for someone). Further, individuals with high levels in D will hold beliefs that serve to justify corresponding behaviors (for example to maintain a positive self-image). There are a variety of beliefs that may serve as justification, including that high-D individuals consider themselves or their group as superior, see others or other groups as inferior, endorse ideologies favoring dominance, adopt a cynical world view, consider the world as a competitive jungle, and so on.
D explicitly represents a fluid construct and will thus be reflected in all indicators used to assess dark traits. Nonetheless, the operational definition of D obviously depends on the specific indicators included. For example, if using an inventory designed to assess Narcissism, the resulting scores will of course primarily reflect Narcissism and only secondarily reflect D. A particular operationalization of D will thus be flavored depending on the dark trait measures included, so that (slight) shifts in meaning are to be expected when different sets of dark traits are investigated. Thus, although the indicators of any particular dark trait will — to a certain extent — also reflect D, measuring D itself requires the inclusion of a sufficiently large number of indicators of diverse dark traits in order to capture the full theoretical breadth that D represents.