Psychopaths, or people characterized by a lack of empathy and remorse and possess very shallow emotions, are generally associated with cold-blooded serial killers and mass murderers, but a new study reveals that U.S. presidents also display certain psychopathic traits that could make them "successful psychopaths."

In fact, researchers from the Emory University suggest that psychopathic traits like fearless dominance may be an important predictor of success in presidential performance.

While there is no question that psychopathy is an extremely problematic condition with those affected possessing maladaptive characteristics like poor impulse control, lack of guilt and an inability to empathize, researchers said that other traits associated with the condition, like fearlessness, lack of anxiety and interpersonal dominance can play a beneficial role in certain occupations, especially leadership positions.

Experts say that not all psychopaths are criminals or dangerous, and the paper published in the Journal of Personality and Social Psychology shows that some of the most successful American presidents exhibited plenty of psychopathic traits, such as fearless dominance, that have been linked to better leadership skills, persuasiveness, crisis management and Congressional relations.

Researchers analyzed personality assessments from more than 100 experts, including biographers and scholars, of 42 presidents, up to George W. Bush, and found that Theodore Roosevelt ranked highest in fearless dominance, followed by John F. Kennedy, Franklin D. Roosevelt, Ronald Reagan, Rutherford Hayes, Zachary Taylor, Bill Clinton, Martin Van Buren, Andrew Jackson and George W. Bush.

The study used data from two large surveys of presidential historians collected by C-SPAN in 2009 and by Siena College in 2010 to assess job performance.

Researchers said that the latest study on presidents offered a glimpse into an emerging theory that some aspects of psychopathy may actually be positive adaptations in certain social situations. "Certain psychopathic traits may be like a double-edged sword," says lead author Scott Lilienfeld. "Fearless dominance, for example, may contribute to reckless criminality and violence, or to skillful leadership in the face of a crisis."

"The way many people think about mental illness is too cut-and-dried," Lilienfeld added. "Certainly, full-blown psychopathy is maladaptive and undesirable. But what makes the psychopathic personality so interesting is that it's not defined by a single trait, but a constellation of traits."

Clinical psychologists characterize psychopaths of possessing a combination of characteristics like self-centered impulsivity, superficial charm, guiltlessness, callousness, dishonesty and immunity to anxiety.

Researchers said that each of these traits lies along a continuum, and all individuals may exhibit one or more of these traits to a certain degree.

"You can think of it like height and weight," Lilienfeld explained. "Everyone has some degree of both, and they're continuously distributed in the population."

Researchers had also measured self-centered impulsivity in presidents and found that in contrast to boldness, the trait was associated to some negative job performance indicators like Congressional impeachment resolutions, putting up with unethical behavior in subordinates and undesirable character.

They noted that Theodore Roosevelt ranked the highest for fearless dominance, but scored lower than average for self-centered impulsivity suggesting that he was far from being psychopathic.

However, Lyndon Johnson scored relatively high for fearless dominance, ranking at number 15, but was also among the top five scorers for self-centered impulsivity.

"That's consistent with what we know about Johnson," Lilienfeld says. "He was a very dominant, socially bold person, at times even ruthless about getting his way. In some sense, these traits may have made him an effective leader, able to push through civil rights legislation, but they may not have been so positive in terms of personal relationships."

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