There Is No Single Age at Which You Are at Your Best

Different mental abilities reach their peak at different ages. Joshua Hartshorne and Laura Germine combined standardized test data with a very large online sample and found that some abilities peak and start to decline around the end of high school, some level off in early adulthood and decline from the thirties, and some do not peak until the forties or later (Hartshorne & Germine, 2015). There is no single age at which a person is at their best on everything at once.

Some abilities keep rising for decades.

Speed of processing is among the first abilities to peak. Knowledge-based abilities follow a different course. In a review of the studies that compared younger and older adults, Paul Verhaeghen found that older adults consistently scored higher on vocabulary (Verhaeghen, 2003). One qualification belongs with that finding: on multiple-choice vocabulary tests, the older adults’ advantage disappeared once differences in education were taken into account.

Researchers still disagree about when decline begins.

Timothy Salthouse has argued that some aspects of age-related cognitive decline begin in healthy, educated adults in their twenties and thirties. He points out that long-term studies can miss this because people get better at the tests simply from taking them repeatedly (Salthouse, 2009).

K. Warner Schaie, who directed the Seattle Longitudinal Study and followed thousands of adults over several decades (Schaie, 1994), replied that Salthouse’s conclusion rests on comparing different age groups at one point in time, which mixes the effects of age with differences between generations (Schaie, 2009). The argument has not been settled, and both positions are held by serious researchers.

Continued practice keeps specific abilities sharp.

Ralf Krampe and K. Anders Ericsson compared older expert pianists with older accomplished amateurs (Krampe & Ericsson, 1996). Both groups showed the usual age-related slowing on general speed tests. On music-related tasks, the amateurs declined with age and the experts largely did not. What predicted how well the older experts held on was how much deliberate practice they had kept doing in later adulthood.

Neil Charness found something similar in chess (Charness, 1981). When he compared players of the same skill level across a wide range of ages, skill predicted how well they chose moves and age did not. Older players matched equally skilled younger players and took less time to settle on an equally good move.

The one thing to do.

Pick the ability your work depends on most, the thing you would least want to lose, and keep practicing it deliberately, at the edge of what you can do, every week. For the older expert pianists, how much they kept practicing predicted how well they held on. The post on the week-three wall describes what that kind of practice looks like.

What this does not show.

The practice findings are specific to the practiced skill. The expert pianists slowed down on general tasks just like everyone else, so this is not evidence that practice protects the mind in general. Most of the research compares groups, and averages hide large differences between individuals: plenty of people outperform their age group, and some decline early. The disagreement over when decline begins is also a reminder that the answer depends partly on how the question is studied.