The current race to the White House has not been short of people questioning the candidates' states of mind. But what happens if you take a more scientific approach?

Oxford University's Dr Kevin Dutton has been exploring the psychopathic traits of the US presidential hopefuls and historical figures using a standard psychometric tool – the Psychopathic Personality Inventory – Revised (PPI-R).

Dr Dutton has spent much of his career looking at psychopaths and researching psychopathic traits, identifying those which can be of benefit and those which can lead to incarceration. He contends that being a psychopath is not an all-or-nothing affair. Instead, psychopathy is on a spectrum along which each of us has our place. There are several professions which seem to attract more than their fair share of those high on the psychopathic scale, among them business, surgery, the law, military and… politics.

Over the past few years, Dr Dutton has contacted the official biographers of many historical leaders and asked them to fill out, on their subject's behalf, an abbreviated version of the Psychopathic Personality Inventory – Revised (PPI-R). As it unfolds, the 'league table' shows that the vast majority are high scorers – including Winston Churchill – especially on the positive aspects like social influence, fearlessness and coolness under pressure. However, analysis also reveals that leaders who possess psychopathy's negative traits – such as self-centredness, impulsivity and a lack of empathy – tend not to do so well in office.

Further to analysing political leaders, Dr Dutton recently turned his attention to the contenders for the US presidency. Working with an anonymous, highly respected and seasoned political correspondent, Dutton has analyzed the psychopathic traits of the then presidential hopefuls Donald Trump, Hillary Clinton, Ted Cruz and Bernie Sanders. Like the historical biographers, the correspondent filled out the PPI-R short version for each of the candidates.

Dr Dutton explained: '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.'

The results clearly show Donald Trump to be higher scoring than rivals, achieving a total score on a par with Hitler and Idi Amin. Of particular interest, Trump outscored the other candidates in 'fearless dominance', the area associated with successful presidencies, and in 'self-centred impulsivity', the set of traits considered negative.

Dr Dutton said: '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 whether their mix of positive and negative traits should send them to the Oval Office.'