Study author Dr Kevin Dutton said: "The PPI-R does not say that someone is or is not a psychopath. It scores them on eight traits that contribute to a psychopathic character.
"Some of those traits, such as fearlessness or stress immunity, can be positive. Others, such as blame externalisation or being unconcerned about the future, are more likely to be negative. One, cold-heartedness, can contribute to good and bad leadership.
"Both great and terrible leaders score higher than the general population for psychopathic traits, but it is the mix of those traits that determines success.
"For example, someone who scores highly for being influential, fearless and cold hearted could be a decisive leader who can make dispassionate decisions. If those traits are accompanied by a high score on blaming others, they might be a genocidal demagogue."
Experts on the political figures were asked to answer 56 questions from the psychopathic personality inventory-revised (PPI-R) test to determine a score.
The test measures personality traits including fearlessness, cold-heartedness, egocentricity, ruthlessness, self-confidence, charisma, dishonesty, and deficits in empathy and conscience.
Mr Trump outstripped Hitler on factors including social influence and fearlessness, while the Nazi dictator scored higher on Machiavellian egocentricity and cold-heartedness.
While ranking lower than her rival overall, Mrs Clinton far exceeded tyrannical Roman emperor Nero on traits such as "Machiavellian egocentricity".
Of particular interest, Trump outscored the other candidates in "fearless dominance", the area associated with successful presidencies.
The findings, published in the he journal Scientific American Mind, found that another high-scoring area for the billionaire businessman, self-centred impulsivity could undermine this, however.
Dr Dutton added: 'It is interesting that these scores reflect both the praise and the criticism that Trump and Clinton receive.
"In the end, while both score relatively highly, it will be up to voters to decide if whether their mix of positive and negative traits should send them to the Oval Office."
History has been littered with famous figures who exhibit psychopathic tendencies, it said, with other high-scorers including Henry VIII who scored a huge 178 points and Winston Churchill on 155.
Other professions in which such characteristics allow an individual to flourish are business, the military and law, the research said.
The Psychopath Test: Who scored highest for psychopathic personality traits
1. Saddam Hussein (189)
2. Henry VIII (178)
3. Idi Amin (176)
4. Adolf Hitler (169)
5. William the Conqueror (165)
6. Saint Paul (157)
7. Jesus (157)
8. Winston Churchill (155)
9. Napoleon Bonaparte (153)
10. Emperor Nero (151)
11. Oliver Cromwell (136)
12. Margaret Thatcher (136)
13. George Washington (132)
14. Elizabeth I (130)
15. Abraham Lincoln (123)
16. Mahatma Gandhi (1
