Sports writers will tell you that athletes peak in their 20s, after which point their skills quickly erode. Most other things in our lives—our careers, for example—take a good deal more time to develop. Intelligence, it turns out, peaks a bit later, too, though with a twist, according to a recent study: Some facets of intelligence peak when we’re still in high school or college, while others continue to improve into our 40s, 50s, and beyond.
Research on intelligence began a century ago with French psychologist Alfred Binet’s work aimed at identifying schoolchildren with learning disabilities in the early 1900s. For a while, psychologists focused on how they could measure intelligence. But more recently, psychologists have been interested in what makes a person intelligent, or, for that matter, whether there is even one single thing we could call intelligence.
(Probably not.) As the latter idea’s taken hold, researchers have wondered how different sorts of intelligence develop over time. Answering that question has implications not only for scientists’ theories of intelligence, but could also improve teachers’ effectiveness, and help doctors identify and address cognitive decline in senior citizens.
To get some answers, psychologists Joshua Hartshorne and Laura Germine tested 21,926 people aged 10 to 71 who had visited the website TestMyBrain.org. There, participants were tested on vocabulary, the ability to encode strings of numbers into symbols, something called the “mind in the eyes” test, an emotion-recognition test which asks people to identify someone’s feelings using only a picture of their eyes, and working memory—that is, the ability to recall recently viewed objects.
The study aims to show that cognitive abilities don’t all peak at the same time or even follow any one trend as people age.
Depending on which of those given measures you’re going by, people peak at very different times. Some of the youngest participants did best on the number-to-symbol coding task, with the peak performance around 19 or 20 years old. After that, performance steadily declined with age. Working memory peaked between the mid 20s to mid 30s before beginning a relatively slow decline.
Those over 40 shouldn’t fret, though. On the “mind in the eyes” test, participants reached near-maximum abilities by their early 20s but kept improving until 48, after which emotion-recognition skills declined very slowly. Vocabulary, meanwhile, climbed with the participants’ age, and gave little sign of slowing down.
The point of the study isn’t really to identify what age we peak at or which ability reaches its apex later. Rather, Hartshorne and Germine write in Psychological Science, the study aims to show that cognitive abilities don’t all peak at the same time or even follow any one trend as people age.
That’s something that has important implications for psychologists’ theories of cognition, according to Hartshorne and Germine. “[T]he complexities described in this article provide a rich, challenging set of phenomena for theories of development, maturation, and aging,” they write. Some of the trends are likely due to the biological decline that inevitably greets us all, while others, such as the steady increase in vocabulary, could be the result of the experience that only old age brings.
This post first appeared at Pacific Standard.