Personality and Cognition
Personality and cognitive ability tests have long been used in job selection. They have both been shown to be important predictors of job performance but are considered separate tests which measure different aspects of job suitability.
An interesting set of studies shows that they may have more in common than previously thought. It has been shown that apsects of personality may actually influence performance on cognitive ability tests!
The studies looked at a personality trait known as Extraversion. Extraverted people tend to seek out social interaction and enjoy the company of others. Introverts are more likely to be reserved and may feel uncomfortable around other people, preferring to be alone or in small groups. One theory of personality, Eysenck’s biological theory, explains these differences in the amount of activity in the brain of extraverts and introverts. Introverts have more activity in a part of the brain known as the ascending reticular activating system (ARAS). This means that they have a higher level of natural ‘arousal’ and can get easily over-stimulated by, for instance, interacting with other people. Whereas extraverts have lower levels of arousal and seek out external stimulation.
The ARAS is also involved in performance on cognitive ability tests that rely on Working Memory. Working Memory is a skill whereby we are able to hold information in mind and manipulate it – an example of this would be performing mental arithmetic or matching new information with other recently learnt information. It is likely that, because they have different levels of natural activity in the ARAS, introverts and extraverts may perform differently on Working Memory tasks.
Studies have shown that to be the case. Extraverts have been shown to perform better on tasks requiring learning and recalling word pairs and digit sets. In both cases, the relevant information had to be held in mind and then compared with the stimulus presented to determine whether it matched (Lieberman, 2000).
Lieberman (2000) explained the outcomes with reference to Eysenck’s theory. Introverts are more cognitively ‘busy’ than extraverts. Tasks that place greater demands on the ARAS may overstimulate introverts so that they don’t perform well on these tasks.
Implications for job selection 
Findings like these can have implications for job selection. Although, it would be hasty to conclude that all introverts will perform badly on Working Memory tasks; the human brain and the interplay between brain, personality and behaviour are complex. Which is why it helps to have people with the right expertise to guide your business when making decisions about who to hire, who to promote and who to retrain.
Our professionals are psychologists and researchers who have extensive experience in developing, administering and interpreting the results of cognitive ability tests, personality measures and other job performance indicators.
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