A new study published in Science Advances challenges the widely held belief that cognitive skills begin to decline starting as early as age 30. Instead, researchers found that literacy and numeracy skills generally improve until at least age 40, after which they either stabilize or decline slightly. However, this decline is not inevitable. People who engage in frequent skill-related activities at work and in everyday life tend to maintain or even improve their cognitive abilities beyond their forties.
The researchers conducted this study to provide a more accurate picture of how cognitive skills change with age. Most previous research relied on cross-sectional data, which compares people of different ages at a single point in time. This approach can be misleading because it does not account for generational differences in education and skill development.
For example, an older person might score lower on a literacy test than a younger person, but this could reflect differences in their educational background rather than a true decline in ability over time. The researchers wanted to separate the effects of aging from these cohort differences by tracking the same individuals over time.
“Cognitive skills have a strong impact on an individual’s labor market earnings and on economic growth of countries. The aging of advanced societies around the world raises concerns about the pattern of skills with individual age. But the existing research had obvious limitations because it did not follow the skills of individuals but instead simply compared individuals of different ages,” explained study author Eric A. Hanushek, a senior fellow at the Hoover Institution of Stanford University.
For their new study, the researchers used data from the German longitudinal component of the Programme for the International Assessment of Adult Competencies (PIAAC-L). This project followed a large, representative sample of German adults who were tested on literacy and numeracy skills twice, with a gap of 3.5 years between assessments. This allowed the researchers to measure real changes in individual skills rather than relying on indirect comparisons between different age groups.
Skill usage was measured through a detailed questionnaire included in the initial PIAAC assessment. Participants reported how frequently they engaged in various reading and math-related activities both at work and in daily life. For reading, they indicated how often they read instructions, emails, articles, books, and reference materials. For numeracy, they reported activities such as calculating costs, using fractions or percentages, and interpreting graphs. Responses were recorded on a five-point scale, ranging from “never” to “every day.”
The research team used statistical methods to account for a common issue in repeated testing: measurement error. When people take tests, their scores are not perfectly accurate. There is always some degree of random fluctuation. This fluctuation can create a misleading impression of skill change over time, a phenomenon known as “reversion to the mean.”
Imagine someone scores very low on a test simply due to bad luck or random error. On a retest, their score is likely to be closer to their true skill level, making it seem like their skills have improved, even if they haven’t. The researchers employed statistical adjustments to minimize this bias and get a more accurate estimate of genuine skill changes with age.
After applying these adjustments, the researchers discovered a pattern quite different from what previous studies had suggested. On average, literacy and numeracy skills actually increased substantially into people’s forties. After this peak, literacy skills showed only a slight decline, while numeracy skills decreased more noticeably. However, these averages hid an important variation. When the researchers looked at skill changes in relation to how frequently people used their literacy and numeracy skills in their daily lives and at work, a striking difference emerged.
For individuals who reported using their skills more often than average, there was no sign of skill decline within the age range studied (up to age 65). In fact, their literacy and numeracy skills continued to improve into their fifties and then leveled off. In contrast, skill decline was primarily observed in individuals who reported below-average skill usage. This suggests that actively using cognitive skills throughout adulthood may be a key factor in maintaining or even improving them.
“Individual behavior dramatically affects the age pattern of cognitive skills,” Hanushek told PsyPost. “Those who use literacy or numeracy skills at home or work can lessen if not eliminate neurological patterns of skill decline.”
“The role of skill usage holds across a wide range of circumstances — across occupations, education levels, and life style differences such as quality of diet and exercise options. Within demographic and behavioral groups, those who use skills in normal activities tend to delay any aging effects on cognitive skills.”
The researchers also examined how these patterns differed across different groups of people. They found that individuals in white-collar jobs and those with higher levels of education, groups known to use their skills more frequently, showed increasing skill levels even beyond their forties, as long as they reported above-average skill usage. However, if people in these groups had below-average skill usage, this positive trend was not observed.
Another interesting finding was that women, on average, tended to experience larger skill losses at older ages, particularly in numeracy. This gender difference was not completely explained by differences in skill usage, suggesting other factors might be at play.
As with any study, there are some limitations to consider. The data only included adults up to age 65, so it cannot tell us about skill changes in older age groups. Also, the study was conducted in Germany, and it is uncertain whether these findings would be the same in other countries with different cultural and educational systems. Future research could investigate skill changes in older populations and in different countries to see how generalizable these results are.
In addition, the study focused only on literacy and numeracy. Future research could explore how other cognitive skills change with age and whether skill usage influences them in similar ways. While the study used robust statistical methods and longitudinal data, it remains observational, meaning it cannot establish cause and effect.
Despite these limitations, this research provides important insights into cognitive aging. It suggests that cognitive decline is not a uniform or inevitable process. Actively engaging our minds and regularly using our literacy and numeracy skills throughout adulthood may play a significant role in preserving and even enhancing these abilities as we age. This offers a more encouraging perspective on aging and highlights the potential for lifelong learning and cognitive engagement to support healthy cognitive function throughout life.
“This work is part of a long term research program into the determinants of cognitive skill differences and the economic and social impacts of any differences,” Hanushek explained. “We see more and more that skill differences have strong impacts on both individuals and nations.”
The study, “Age and cognitive skills: Use it or lose it,” was authored by Eric A. Hanushek, Lavinia Kinne, Frauke Witthöft, and Ludger Woessmann.