The results indicated that older individuals have higher aptitude for crystallized intelligence than their younger co-workers. However, fluid cognitive abilities showed large declines with age, as did inductive reasoning. Overall, mental ability seemed to decrease gradually across age groups relative to applicants under age 30, with more marked declines for groups older than 59. The researchers replicated these findings in several large, representative general population samples.

The results pose a dilemma for employers, which may unwittingly be hiring with an age bias depending on what tests they are administering.

"Given the rising numbers of older employees in the workforce, as well as the rise in age-based discrimination cases, it is increasingly important for employers to be careful regarding which tests of cognitive abilities they administer," said study lead researcher Rachael M. Klein, a doctoral candidate at the University of Minnesota.

In the meantime, older workers might also benefit from keeping their skills updated to compete with younger counterparts.

“Older workers should continue to make use of training opportunities offered to keep their knowledge and skills relevant,” says study co-author Stephan Dilchert, an assistant professor at the Zicklin School of Business at CUNY's Baruch College.

On the other hand, some professions require and value experiential intelligence. According to Dilchert, many highly complicated and prestigious career fields such as medicine and law are very compatible with those individuals who possess superior crystallized cognitive abilities.

“Ultimately, job-relevant knowledge and skills are the factors that directly relate to performance in any job – and demonstrating them can be just as important as demonstrating ‘raw’ cognitive ability,” says Dilchert.