In the age of the Internet selfie, the new normal for narcissistic self-indulgence might be harder to gauge with practitioners ranging from Everyman to the president of the United States. What is now sane in a world gone mad?

Perhaps sanity may be defined in degrees, and measured by the number of selfies shot throughout the day — the behavior outing some as true narcissists. At one end, people who tend to overindulge in self-photography suffer from body dysmorphic disorder and obsessive compulsive disorder, while the behavior outs others as true narcissists, a more nefarious breed.

According to the Mayo Clinic, people whose narcissism rises to a clinical threshold suffer a mental disorder. They believe they’re superior to others and feel little empathy for others, though their boisterous self-confidence belies a soft psychological core, highly sensitive to criticism. At worst, people who suffer from narcissistic personality disorder experience trouble with relationships, both personal and professional.

Not surprisingly, narcissists are most likely to cheat on their spouses, with men feeling less “sexual empathy” toward their wives and girlfriends, according to researchers James K. McNulty and Laura Widman, from the University of North Carolina at Chapel Hill and Florida State University.

The interdisciplinary pair studied 123 newlywed couples for several years after the nuptials, surveying them at varying times about marital satisfaction, sexual satisfaction, and infidelity. The men and women answered questions about “sexual narcissism,” which the researchers defined as possessing an inflated sense of one’s sexual self, with feelings of sexual entitlement paired with a reduced level of sexual empathy for one’s partner.

The respondents were rated on a five-point scale with phrases such as, "I could easily convince my spouse to have sex with me if he or she was unwilling,” or "I really know how to please my spouse sexually.” These more narcissistic people were more likely to report attitudes that some might refer to as “rapey.”

McNulty and Wildman said the study suggests that people who display such behavioral traits — reviewing their Facebook page right now — may be much more likely to cheat sexually. “Interventions may benefit from identifying and targeting individuals who have narcissistic tendencies that manifest in the sexual domain," they wrote in the study. The findings also stress the benefits for researchers in using measures of sexual narcisissm to reasearch sexual behavior.

Source: McMulty, James K., Wildman, Laura. Archives of Sexual Behavior. 2014.