What percentage of your new hired turn out bad? What does that says about your selection process?

Now I know what you are thinking, your interview process is really well designed, and you hardly ever hire the wrong candidate. Occasionally, a bad hire slips through the cracks and makes it into the organisation, but that’s inevitable right?

Yes, while that’s true that no selection process could ever be 100% effective all the time, how many low performers is your process letting through? What does this say about the quality of your hiring systems?

Statistically speaking, finding low performing candidates is actually pretty hard work. Job performance, as with most psychological constructs, follows the normal distribution (also known as a Gaussian distribution, or the bell curve), as seen below.

But research is now starting to show that it’s not a simple as “Personality vs Intelligence”, and instead these two factors interact with each other in fascinating and unexpected ways.

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Cognitive Buffering

Have you ever met an introvert that gives amazing presentations? Or a highly neurotic person that never seems to fold under pressure?

The odds are, those people were pretty smart.

This is phenomenon is known as “cognitive buffering”, where high cognitive ability acts as a buffer against natural behavioural dispositions. Cognitive ability affords individuals greater control over the expression of their personality characteristics, helping them inhibit or enhance aspects of their personality.

Extraversion ceases to be an advantage for smart people, as cognitive buffering allows introverts to compete on an even keel.

For example, when smart introverts are required to give presentations, cognitive resources can be applied to suppress the negative effects of being introverted. A side-effect however, is that extraversion ceases to be an advantage for smart people, as cognitive buffering allows introverts to compete on an even keel.

Research shows this occurs with both conscientiousness and neuroticism, the two traits most commonly associated with job performance. In both cases, the predictive validity of these personality traits declines as the cognitive ability of the participants increases.

This has two major implications:

  • Smart people can override aspects of their personality using cognitive ability
  • Personality traits stop predicting performance in smart people

However, in employees with lower cognitive ability, things get even more interesting.

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Intelligence Compensation Hypothesis

Surprisingly, research shows a slightly negative relationship between intelligence and conscientiousness. It is hypothesised that individuals with lower cognitive ability develop higher levels of conscientiousness out of necessity, helping them compete against other individual’s higher cognitive ability. Those with higher cognitive ability however find tasks comparatively easy, having less need to develop conscientiousness. The explanation for this phenomenon is known as the “Intelligence Compensation Hypothesis”.

"Conscientiousness makes a significant difference in performance among lower cognitive ability individuals."

- Ben Schwencke

But unlike high cognitive ability-low conscientiousness individuals, low conscientiousness-low cognitive ability individuals cannot employ cognitive buffering. As a result, conscientiousness makes a significant difference in performance among lower cognitive ability individuals, making it a valuable employee selection criterion.

This effect is also seen at the role-level. Conscientiousness shows comparatively lower levels of predictive validity in complex roles, but significantly greater levels of validity in simpler, more routinised roles. Naturally, as simpler roles do not require high levels of cognitive ability, personality factors are the major determiner of performance. However, in more complex roles which are disproportionately filled by high cognitive ability employees, cognitive buffering negates any advantages or disadvantages of personality traits, nullifying their predictive validity.

This also has two major implications:

  • Desirable personality traits compensate for lower levels of cognitive ability to some degree.
  • Personality traits are significantly more predictive of performance in those with lower cognitive ability.
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Paradoxically, personality traits are simultaneously both more, and less important in predicting future performance than previously thought. When candidates show low levels of cognitive ability, personality traits make a world of difference, helping them compete against those with higher cognitive ability. But in candidates that show high levels of cognitive ability, personality pales into insignificance due to cognitive buffering. This explains why personality traits typically only show modest levels of validity overall, as the true picture is being masked.

A few caveats...

Personality traits may not be predictive of performance in high cognitive ability individuals, but what about job satisfaction or employee retention?

Is cognitive buffering sustainable, or does overriding your behavioural dispositions inevitably put you at risk of quitting? What are the long-term effects of doing an extravert’s job as an introvert on job satisfaction and employee engagement?

The best way to not waste your time interviewing is by adopted a skills-based hiring approach which focuses on directly measuring the skills you need for your organisation, rather than inferring them through an interview. Learn more about skills-based hiring.


Perkins, A. M., & Corr, P. J. (2006). Cognitive ability as a buffer to neuroticism: Churchill’s secret weapon? Personality and Individual Differences, 40(1), 39-51.

Postlethwaite, B., Robbins, S., Rickerson, J., & McKinniss, T. (2009). The moderation of conscientiousness by cognitive ability when predicting workplace safety behavior. Personality and Individual Differences, 47(7), 711-716.

Rammstedt, B., Danner, D., & Martin, S. (2016). The association between personality and cognitive ability: Going beyond simple effects. Journal of Research in Personality, 62, 39-44.

Schmidt, F. L., & Hunter, J. E. (1998). The validity and utility of selection methods in personnel psychology: Practical and theoretical implications of 85 years of research findings. Psychological bulletin, 124(2), 262.

Shaffer, J. A., & Postlethwaite, B. E. (2013). The Validity of Conscientiousness for Predicting Job Performance: A meta‐analytic test of two hypotheses. International Journal of Selection and Assessment, 21(2), 183-199.

Wood, P., & Englert, P. (2009). Intelligence compensation theory: A critical examination of the negative relationship between conscientiousness and fluid and crystallised intelligence. The Australasian Journal of Organisational Psychology, 2, 19-29.

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