Is Intelligence Important in the Workplace?

A widespread misconception exists that intelligence matters in academic settings but holds little importance for workplace success. Some believe that IQ only correlates with occupational prestige because professional positions require college degrees, and that among those actually employed in a given role, intelligence shows no relationship with job performance. This belief is incorrect.

After demonstrating that intelligence tests could predict academic achievement, early researchers examined their relevance to the workplace. Terman's studies in 1916 revealed that unemployed individuals were more likely to possess lower intelligence scores. World War I provided extensive data through the Army Alpha and Army Beta tests, which assessed approximately 1.73 million military recruits. These examinations revealed that higher-scoring individuals received better performance ratings from commanding officers (r = .536), achieved higher military ranks, completed training more successfully, and encountered fewer disciplinary issues.

The military data also demonstrated that intellectually capable individuals could handle more sophisticated roles. Officers in engineering, medicine, and accounting positions showed the highest intelligence levels, while laborers and general workers displayed the lowest scores. This pattern has been consistently replicated in civilian employment, where attorneys, engineers, and research analysts average IQs of 114-118, compared to 87-91 for custodians, food service workers, and warehouse employees. Intelligence functions as a "gatekeeper" for numerous occupations, establishing minimum cognitive requirements through job demands and educational prerequisites rather than explicit testing.

Intelligence doesn't merely influence occupational access—it also predicts workplace performance. Early research showed mixed results across different positions, but methodological advances in the 1970s revealed that statistical artifacts had obscured true patterns. Meta-analyses demonstrated that job complexity determines the strength of the intelligence-performance relationship. In highly complex positions (employing roughly 15% of workers), intelligence correlates approximately r = .58 with job performance. In the simplest roles (only 2.4% of workers), this correlation drops to r = .23.

Among various employee selection methods for medium-complexity positions, IQ (r = .51) ranks as one of the strongest predictors of job performance, surpassed only by work samples (r = .54). Combining intelligence assessment with integrity testing yields the most accurate predictions (r = .65). These correlations matter because they represent efficiency gains over random selection. Using intelligence tests improves hiring efficiency by 51% compared to chance, making it particularly valuable in competitive industries where recruitment decisions significantly impact organizational success.

Intelligence likely influences job performance indirectly by enhancing employees' ability to acquire job-relevant knowledge and skills, whether through formal education or on-the-job training. This accumulated knowledge then translates into superior work performance.

Despite intelligence testing's demonstrated value, few American employers utilize it, primarily due to the 1971 Supreme Court ruling in Griggs v. Duke Power Co. This decision established that employment tests must directly relate to job duties and that employers must justify any selection procedures producing disproportionate demographic outcomes. Consequently, only about 10% of contemporary employers administer cognitive ability tests to entry-level applicants.

Organizations have adopted alternatives including work samples, structured interviews, and job-specific knowledge assessments. Many employers favor college-educated candidates as educational attainment correlates strongly with intelligence and signals cognitive capability for medium-complexity work.

Some theorists argue that experience or extensive training can eliminate intelligence's predictive value. However, research contradicts this "training hypothesis." While additional preparation may temporarily boost lower-IQ workers' performance in simple, routine positions, intellectually capable employees eventually surpass better-trained colleagues in moderately complex roles because they acquire knowledge more rapidly, retain information more effectively, and develop superior informal job understanding.

The evidence overwhelmingly confirms that intelligence significantly impacts workplace success, influencing both occupational access and job performance across most careers.





From Chapter 23 of "In the Know: Debunking 35 Myths About Human Intelligence" by Dr. Russell Warne (2020)