Research shows that intelligence declines not with aging but with 'not using one's head,' and that people who use their heads often continue to develop their abilities even as they get older
It is generally said that cognitive function begins to decline quite early in life, in people's 20s and 30s, and the decline in skills due to aging is a serious threat to modern society, where the aging population is rapidly increasing. However, a German study that looked at how skills such as writing ability and arithmetic ability change with age found that people who use their brains a lot in work or other activities continue to improve their skills even in old age.
Age and cognitive skills: Use it or lose it | Science Advances
https://www.science.org/doi/full/10.1126/sciadv.ads1560
Reading, math skills boost cognitive abilities and prevent brain aging in seniors - CHOSUNBIZ
https://biz.chosun.com/en/en-science/2025/03/06/VHGQLWTFMBFUPFAU3I77WW572Q/
In a study published in the peer-reviewed journal Science Advances on March 5, 2025, a research team from Stanford University in the United States and the Berlin School of Economics and Political Science and the University of Munich in Germany analyzed the performance of ability tests taken by adults aged 16 to 65.
The tests were part of the OECD's Project Internationala de Adolescence (PIAAC) and , unlike other countries, Germany was also conducting an additional research project, PIAAC-Longitudinal, which repeated the tests after three and a half years, allowing the researchers to accurately measure changes in cognitive skills as people age.
The average age of the 3,263 German participants who took the test twice was 41.3 years old. 37.8% of them worked in white-collar jobs (management, professional or technical positions) and 30.6% had a higher education.
First, the results of the first test conducted in 39 countries around the world are below. A total of 147,667 people participated in this test, and it was found that literacy (left) and arithmetic (right) were highest in people in their 20s and 30s, and dropped significantly after their 40s.
Because one-time tests cannot rule out the possibility that the relationship between age and skill decline is due to generational differences rather than aging, the team looked at changes in literacy and numeracy skills over time, and a very different pattern emerged than in the cross-sectional data.
The graph below shows data from Germany, where two tests were conducted at different times. The top graph shows the relationship between age and skill, and the bottom graph shows the rate of change in skill by age. First, reading and writing ability rose significantly in the 20s and 30s, leveled off in the late 30s, and peaked at age 46, but there was only a limited decline thereafter. Mathematics ability also declined significantly after peaking at age 41, but never fell below the level of the early 20s.
The results are even more striking when we separate those who use skills frequently (red line) from those who use them infrequently (blue dashed line): those who use skills frequently do not decline in literacy and numeracy skills, but rather continue to develop them into their 60s. On the other hand, those who use skills infrequently begin to lose ability in their mid-30s.
Similar results were obtained when dividing the analysis by whether the job was white-collar (red line) or blue-collar (blue dashed line) (top row), and by whether the job was highly educated (red line) or not (blue dashed line) (middle row). In addition, when dividing the analysis by women (red line) and men (blue dashed line) (bottom row), it was found that women's skills decline from their 40s. The research team points out that part of the reason for the significant gender difference in math skills is that men use math more frequently.
The researchers say that it's the frequent use of your brain that matters most, because even among white-collar and highly educated people, only those who use their skills frequently show improvement in their abilities after their 40s. Similarly, among blue-collar and less educated groups, those who use their skills frequently show no decline in abilities as they get older.
The research team emphasized the importance of lifelong learning, saying, 'Only those with below-average skill use experienced a decline in skills as they grew older; white-collar and highly educated workers with above-average skill use continued to increase their skills even after their 40s. The finding that skill utilization can avoid cognitive decline is good news for countries with ageing societies, but maintaining skills is not automatic and appears to depend on the stimulation of utilizing skills.'
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