(Image: HBO)

From Frank Underwood in House of Cards to Cersei Lannister in Game of Thrones, there’s a trait that some of our most memorable villains have in spades: Machiavellianism. Yet until recently this has been overlooked by most of personality science.

Psychologists have long thought that measuring someone on a scale of just five personality dimensions – agreeableness, extroversion, neuroticism, conscientiousness and openness to new experiences – can capture all the variation in behaviour and attitude seen in the human race.

But it turns out that we may have been overlooking a crucial sixth personality trait – and it’s not a pretty one. It’s known as honesty-humility, but it’s people who are lacking in those two qualities that the measure is designed to pick out.


Dark side of you

Some psychologists believe that standard personality tests based on the “big five” are failing to identify people who are sly, dishonest and greedy. “These are people who lack moral character,” says Taya Cohen of Carnegie Mellon University in Pittsburgh.

Cohen says that “agreeableness” goes some way to measuring these undesirable traits, but only in the way we react to others – not in the behaviours we initiate. “Agreeableness captures people’s patience and forgiveness but not the actively harmful behaviours. Honesty-humility really captures that Machiavellianness,” she says.

The trait is part of a new six-factor model (see how you score here). But almost all the supporting evidence for its inclusion has been based on people doing questionnaires and giving their opinion of how likely they are to behave and think in certain ways.

Now a study has shown that people who score low on the honesty-humility trait are more likely to be dishonest in a series of lab tests. In one test of 88 people, those who cheated in a dice-rolling game to win small sums of cash had lower honesty-humility scores – but there was no link with any of the big five traits. Those in the lowest bracket for the trait claimed to have predicted a dice-roll correctly about 75 per cent of the time when their real odds of doing so were only 17 per cent.

Cheat to the top

“They were cheating like mad,” says co-author Benjamin Hilbig of the University of Koblenz-Landau in Germany.

Ivan Robertson of the University of Manchester, UK, says the six-trait model does seem better at teasing out Machiavellian personality traits. But he points out that the big five is widely used, and introducing new models will make it harder for researchers to compare their work.

Cohen thinks acceptance of the big six is growing. She investigates integrity in the workplace and finds the honesty-humility trait invaluable for measuring how likely people are to do things like cheat on their time-sheets or steal office supplies. “If they have the opportunity to behave in a very selfish way, they do so, even if it might harm others,” says Cohen. “They can be nasty to co-workers too.”

Journal reference: Journal of Research in Personality, doi.org/45b