In the past two years the study of narcissism has gotten a face-lift. The trait is now considered to have two distinct dimensions: admiration seeking and rivalry. Subsequent studies, including a recent look at actors, revealed a more nuanced picture of personality than did past work. The actors, for instance, want admiration more than most people but tend to be less competitive than the average Joe—they may crave the spotlight, but they will not necessarily push others out of the way to get it.

The new understanding of narcissism started with a 2013 paper in the Journal of Personality and Social Psychology that identified narcissism's two dimensions. “Previous theories and measures of narcissism dealt with this trait as a unitary construct, mixing up agentic aspects—assertiveness, dominance, charm—with antagonistic aspects—aggressiveness and devaluation of others,” says Mitja Back of the University of Münster in Germany, the study's primary author. Lumping both aspects together made narcissistic behavior confounding.

Studying hundreds of healthy subjects, Back's team found that traits related to narcissism clustered into two categories, with both facets of narcissism serving to maintain a positive self-image. Self-promotion draws praise, whereas self-defense demeans others to fend off criticism. Admiration seeking and rivalry each have different effects on body language, relationship health and personality.

In the latest paper to build on these findings, in press in Social Psychological and Personality Science, actors and acting students were rated by themselves and others as more hung up on admiration than nonactors. But although winning plum roles requires competing with fellow thespians, working with others demands collaboration, and this aspect also attracts actors: the actors were found to be less rivalrous than the nonactors. Hollywood, then, may be predictably full of egotists but not jerks. The research was led by Michael Dufner of Leipzig University in Germany, who collaborated with Back on both papers.

It pays to be aware of narcissism's duality. “What attracts us in social partners at first sight is not necessarily what makes us happy in long-term relations,” Back says. Even if narcissists have that bright, charming side, it is often simply a matter of time before the clouds come out. Except, perhaps, on Broadway.