How to do it
- Take on more of the second. The judgement call, the history, explaining how it really works.
- Pass some of it on. Mentoring one named person is the concrete version.
- Keep doing some fast, new things too. This is about where you put the weight, not dropping them.
What ages which way
- Speedpeaks early
Processing speed, how fast you take in and handle something new, peaked in the late teens in about 48,000 people tested online.
- Knowledgepeaks late
Vocabulary peaked around 65 in the online data, and tasks that run on learned knowledge all peaked late. There was no single age when everything peaked.
- Your workmixes both
Most jobs need some of each. Which one yours leans on is the question to ask. That's reasoning, not a finding.
- Youshift the weight
Moving your week towards what you know is Arthur Brooks's idea, taken from findings like these. Nobody has tested it.
Why it works
Your mind doesn't age in one direction. In about 48,000 people tested online, different abilities peaked decades apart. Evidence: decent Processing speed, how fast you take in and handle something new, peaked in the late teens. Vocabulary peaked around 65 in the online data, and around 50 in older standard test norms; every task that runs on learned knowledge peaked late. Evidence: decent The study compared people of different ages at one point in time rather than following anyone for years. Evidence: decent
Arthur Brooks, who writes about happiness and work, takes this further. He splits thinking into fluid intelligence, working out new problems fast, and crystallised intelligence, what you've built up and know. His advice: in the second half of a career, move towards work that runs on the second kind. That's his extrapolation from findings like these. Nobody has tested whether it makes men happier or better at their jobs. Evidence: worth trying
The long readEvery step of the chain, each study with its numbers, and what's still unproven. 2 min read.
What happens in your brain
This chain is about abilities and work, not brain areas. The first two stops come from one study. The last two are Brooks's idea and my reading of it.
Speed peaks early. Processing speed peaked in the late teens. Evidence: decent
Knowledge peaks late. Vocabulary peaked around 65 in the online data, and the other knowledge tasks also peaked late. There was no one age at which everything peaked. Evidence: decent
Your work mixes both. Most jobs need some of each. Which one yours leans on is the question to ask. That's reasoning, not a finding. Evidence: worth trying
You shift the weight. Moving your week towards what you know is Brooks's idea. It's untested. Evidence: worth trying
The proof
- Hartshorne and Germine, 2015: 48,537 people tested online, plus standard IQ and memory test norms, compared by age at one point in time. Different abilities peaked decades apart. Evidence: decent
- Processing speed peaked in the late teens; working memory around 30. Evidence: decent
- Vocabulary peaked around 65 online and around 50 in the older test norms. Five tasks that run on learned knowledge, including general information and arithmetic, peaked later than nearly everything else. Evidence: decent
- The career shift is Brooks's extrapolation. No study I have tests it. Evidence: worth trying
How to do it
- List what you do in a normal week. Mark each item: does it run on speed, or on knowing things?
- Take on more of the second: the judgement call, the history of the thing, explaining how it really works.
- Pass some of it on. Mentor one named person is the concrete version.
- Keep doing some fast, new things too. This is about where you put the weight, not dropping them.
Watch out
The figures are averages across tens of thousands of people, not a forecast for you. Evidence: decent The study compared different people at different ages; it didn't follow anyone over time, so part of the gap may be generational. Evidence: decent A peak is where an average tops out, not a cliff.
The career shift is Brooks's reading of the data, not a tested plan. Evidence: worth trying
If your memory is slipping in ways that get in the way of daily life, that's a different matter. Getting older has where the line is.