Mental speed declines after age 60, research suggests

Mental agility had previously been thought to peak around age 20

Residents take part in activities to mark International Day of Older Persons. As humans age, it takes longer to react to changes in the environment. Reuters

Mental speed does not start to slow until people turn 60, four decades later than previously thought, a study has suggested.

Researchers say their analysis of more than a million people challenges previous assumptions that mental speed peaks at age 20.

As humans age, it takes longer to react to changes in the environment or stimuli.

This slowing of response time starts from the age of about 20, gradually continuing to slow as people age.

The new study found that although response times started to slow after 20, this could be because people make more cautious decisions and engage in processes not linked to decision-making at a slower rate, such as taking more time to press a computer key.

However, the mental process of making decisions does not start to slow down until age 60, after which it progressively declines.

Mischa von Krause of Heidelberg University in Germany and colleagues looked at data from more than one million people who took part in an online experiment that measured their reaction times to a mental task.

Participants had to categorise a selection of words and images that flashed up on a screen as belonging to one of two categories, for example good or bad, by pushing the correct key in response.

Despite a widespread belief in age-related slowdowns in mental speed, the findings highlight that, for much of life and during the span of a typical career, this is not likely to be the case.

“Our results indicate that response time slowing begins as early as age 20, but this slowing was attributable to increases in decision caution and to slower non-decisional processes, rather than to differences in mental speed,” said the researchers, writing in Nature Human Behaviour.

“Slowing of mental speed was observed only after approximately age 60.

“Our research thus challenges widespread beliefs about the relationship between age and mental speed.”