Ask people when the mind is at its best and most will say somewhere in their twenties. After that, the story goes, it's a long, slow slide.
In 2015 two researchers, Joshua Hartshorne and Laura Germine, tested that story with an unusually large data set: online cognitive tests taken by nearly 50,000 people for their main study, drawn from close to 3 million people who had used their research websites over several years. Their summary was blunt. "At any given age, you're getting better at some things, you're getting worse at some other things," Hartshorne told MIT News. "There's probably not one age at which you're peak on most things, much less all of them."
Slide through a life
Peak ages are the averages reported from Hartshorne & Germine's work and Germine's earlier face-recognition study. "Past peak" means a gradual average decline, not a cliff, and individuals vary enormously. The tool only says which side of the peak an average person is on; it doesn't show how big the changes are.
There is no age at which you are best at everything. Every decade you're gaining on something.
What's going on
The early peaks are abilities that lean on raw speed, the kind of tasks psychologists call fluid: handling new information quickly, holding several things in mind at once. Raw processing speed tops out around 18 or 19. Short-term memory keeps improving until about 25, holds steady, and starts to drop around 35.
The late peaks lean on accumulated experience, which psychologists call crystallised knowledge. The ability to read other people's emotional states peaked in people's 40s or 50s. Vocabulary kept growing into the late 60s or early 70s, later than older IQ-test data had suggested.
That trade is the real shape of adult development: speed is gradually exchanged for knowledge, pattern recognition and judgement. A 25-year-old may learn a new app faster. A 60-year-old is more likely to know what the email in front of them really means.
You keep changing in other ways too
| Personality | A 2006 meta-analysis pooling 92 samples from long-term studies found that people tend to become more conscientious, more emotionally stable and more socially confident as they age, especially between 20 and 40, and that four of six trait groups kept changing into middle and old age. |
| The brain | Adult brains still physically adapt. Trainee London taxi drivers who spent years memorising the city's streets and passed the exam showed growth in the back of the hippocampus. Trainees who failed and people who didn't train showed no such change. |
| Big life tasks | Work, partnership, parenting, caring for parents and leading others all keep demanding new skills well past any "grown-up" milestone. (See What Every Age Needs for Erikson's map of these later chapters.) |
Read the fine print
Two cautions keep this honest. First, most of these results compare different people at different ages at a single moment, rather than following the same people for decades. People born in different decades grew up with different schooling, nutrition and technology, and that can blur the age curves. Second, these are averages. Some 70-year-olds out-think most 30-year-olds, and health, education, sleep and practice all move the lines.
What the averages do settle is the shape of the story. It isn't a hill with one summit. It's a range, with different peaks reached at different stages of the walk.
Adult development doesn't stop at 18 or reverse at 30. Raw speed peaks in the late teens and short-term memory in the mid-20s, but face recognition peaks around the early 30s, reading other people's emotions in the 40s or 50s, and vocabulary in the late 60s or early 70s. Personality keeps maturing, and adult brains still physically adapt to demanding learning. At every age you're losing a little on some fronts and gaining on others.
Try this: set the slider to your age and to the age of someone much older or younger whom you work or live with. Name one thing each of you is likely better at right now, and next time you'd usually compete with them, trade on it instead.
Sources. Hartshorne, J.K. & Germine, L.T. "When does cognitive functioning peak? The asynchronous rise and fall of different cognitive abilities across the life span." Psychological Science, 2015; peak ages and quotes as reported by MIT News (March 2015). Face recognition peaking in the early 30s: Germine et al., 2011. Personality change: Roberts, Walton & Viechtbauer, Psychological Bulletin, 2006 (92 samples). Taxi drivers: Woollett & Maguire, "Acquiring 'the Knowledge' of London's layout drives structural brain changes," Current Biology, 2011.
- 🌐 MIT News — "The rise and fall of cognitive skills" (the study, in plain language)
- 🌐 TestMyBrain.org (Germine's research site; take real tests and contribute data)
- 📘 The Mature Mind — Gene D. Cohen (a psychiatrist on the strengths of the second half of life)