The sixth personality factor the Big Five forgot

Ask someone to name the traits that make up personality, and if they know anything about the science, they'll give you five: openness, conscientiousness, extraversion, agreeableness, neuroticism. The Big Five. It's the model behind most personality research of the last forty years, and it's the model behind most hiring assessments still in use today.

It's also missing something. There's a sixth factor, and it happens to be the one most directly tied to whether someone can be trusted.

The factor the Big Five never measured

The model is called HEXACO, and the name gives away the difference: Honesty-Humility, Emotionality, eXtraversion, Agreeableness, Conscientiousness, and Openness. Five of those six line up closely with the Big Five's traits under different names. The sixth, Honesty-Humility, doesn't have an equivalent anywhere in the older model. It isn't a renamed version of something else. It's a dimension the Big Five simply doesn't have a slot for.

Honesty-Humility measures something specific: a person's tendency toward fairness, sincerity, and modesty, versus a willingness to manipulate, exploit, or take more than their share when they think they can get away with it. It's not about confidence or warmth, which the other five factors already cover in their own ways. It's about what someone does when no one's checking.

Why one missing factor matters more than it sounds

Here's the part that should concern anyone still relying on a five-factor assessment: Honesty-Humility is the strongest single personality correlate of counterproductive work behavior on record, at approximately −0.48 with workplace deviance. That's a well-established finding, not a single study you'd want to hedge on.

A five-factor test can tell you a candidate is conscientious, agreeable, and calm under pressure. It cannot tell you whether that same person cuts corners, takes credit that isn't theirs, or quietly erodes trust once they're confident no one's watching. That's not a small gap. It's the one dimension most closely tied to the risk every hiring manager is actually trying to screen for, and it's invisible to the model everyone defaults to.

The other thing most tests skip: facets

HEXACO's other advantage barely gets talked about, and it has nothing to do with Honesty-Humility specifically. Most personality models stop at the factor level, one number per trait. HEXACO, in its fuller form, breaks each factor down into facets, its component parts.

Take conscientiousness. Two people can score identically on it and still be completely different to manage. One person's conscientiousness might come from organisation: they plan meticulously, they keep things tidy, they rarely lose track of a detail. Another person's identical score might come from diligence: they grind through the work regardless of how it's organized, finishing things by sheer persistence rather than by planning ahead. Same number. Different person. A factor-level score can't see the difference. A facet-level score can.

That's the real argument for reading HEXACO at facet resolution rather than stopping at the factor. It's the difference between a personality description general enough to fit almost anyone and one specific enough to actually tell you something.

How we use it

We estimate a HEXACO-based profile from a conversation, not a written questionnaire someone fills out. HEXACO is the one instrument in our set we read at the facet level, for exactly the reason above.

The Big Five isn't wrong. It's just missing a factor, and the factor it's missing happens to be the one most worth knowing before you hire someone.