The Rise and Fall of IQ: The Cognitive Divide

IQ may be declining, but with the right attention to how we nurture our minds, we can ensure that human intelligence remains a broad and powerful force, capable of rising to meet whatever challenges.

For most of the 20th century, IQ scores steadily climbed, a phenomenon so consistent it was named the “Flynn effect” after the psychologist James Flynn, who first documented it. Generations across the globe were getting smarter, or at least, their scores on intelligence tests were improving. Explanations ranged from better nutrition and healthcare to more complex societies that required sharper minds. But now, as we move further into the 21st century, the Flynn effect seems to be crumbling. In some countries, the rise has plateaued; in others, it has reversed. What is going on? Are we getting dumber, or is something else at play?

A timely study by Sandra Oberleiter and her colleagues has provided an answer that is both unsettling and enlightening. Published in Intelligence, their research suggests that the Flynn effect is faltering because the nature of intelligence itself is shifting. The problem isn’t that we’re getting dumber. It’s that we’re getting more specialized, and that, in turn, is weakening the ties that bind our cognitive abilities together. In short, modern life is forcing us to become experts at the expense of being generalists.

A Century of Cognitive Growth

To appreciate what’s happening today, we must first understand what made the Flynn effect so fascinating. Between the early 1900s and the turn of the millennium, IQ scores in countries like the United States, the UK, and Germany were rising by about 3 points per decade. This was true for a range of cognitive abilities, from problem-solving to abstract reasoning. The explanations were numerous: better schooling, fewer malnourished children, even the intellectual demands of navigating a world with television, computers, and the internet. The Flynn effect seemed to reflect human progress itself, a testament to our ability to evolve cognitively alongside technological and social change.

But beneath this story of rising intelligence lurked a less explored detail: the gains were not uniform across the population. The biggest increases tended to show up in the lower half of the cognitive ability distribution. In other words, those who started with lower IQ scores benefited most. This observation was first made decades ago and explained as a narrowing of the gap between the cognitive “haves” and “have-nots.”

But now, in the 21st century, this trend has become more complex and erratic. If as Sandra Oberleiter’s research suggests, the positive manifold that links different cognitive abilities is weakening, then this shift has profound implications for inequality.

The Positive Manifold: The Glue of Intelligence

At the heart of Oberleiter’s study is a concept called the “positive manifold”, the idea that different cognitive abilities are positively correlated. A tad simplified …but if you are good at one type of mental task, you’re likely to be good at others. This has long been the bedrock of intelligence testing. Its why IQ tests can give a single, overarching score despite measuring a variety of abilities. The positive manifold reflects a kind of mental coherence: the more integrated your abilities, the higher your general intelligence.

But according to Oberleiter’s research, the positive manifold has been weakening over the last two decades. People are still getting better at specific cognitive tasks, like verbal reasoning or numerical problem-solving, but those improvements don’t translate as well into overall intelligence. In other words, we’re becoming cognitive specialists rather than generalists. This weakening of the positive manifold could explain why IQ gains have slowed or reversed in some countries. It’s not that we’re losing intelligence per se, but that our minds are evolving to meet the demands of a highly specialized world.

The Specialist’s Dilemma: A Cognitive Decathlete

To make this abstract concept more concrete, Oberleiter uses a fabulous metaphor -imagine the cognitive equivalent of a decathlete, someone who competes in ten different track and field events. Decathletes must be competent across a wide range of physical skills: sprinting, jumping, throwing, endurance. The positive manifold is like the overall athleticism that ties those abilities together. But what if our decathlete decided to focus exclusively on the hurdles? They might become an exceptional hurdler, but their performance in other events would likely suffer. Even if their overall decathlon score stayed strong, the correlation between their skills would weaken. This is what’s happening in our minds: we’re training ourselves to excel in narrow domains, but as a result, our general cognitive abilities, the positive manifold, are fraying.

The Rise of Specialization

Why is this happening? Look around. Modern life demands specialization. Children are trained in specific disciplines earlier than ever before. High schools now teach coding and advanced mathematics, subjects that were once the province of university students. The workplace, too, has fractured into niches. Doctors, for example, used to be generalists. Today, they specialize in narrower fields like pediatric endocrinology or interventional cardiology. The trend is everywhere: from the educational system to professional life, society increasingly rewards mastery in specific domains. Clearly specialization can lead to greater innovation and productivity in specific fields. But is it also one of the reasons for the Great Stagnation?

Oberleiter’s study reflects this shift. By analyzing two large samples of IQ data from 2005 to 2024, the researchers found that while people were still improving in specific cognitive areas, the overall interconnections between those areas were weakening. People were getting better at certain mental tasks, but those improvements didn’t map as well onto general intelligence. It’s as if our mental decathletes have become world-class hurdlers but can no longer throw a javelin or clear a high jump.

The Consequences of Cognitive Narrowing

This shift toward specialization raises important questions about the future of intelligence testing and education. If society continues to value narrow expertise over general competence, what will happen to our broader cognitive abilities? Will we keep seeing a decline in the positive manifold, and with it, an end to the Flynn effect? And what does this mean for how we design educational systems? Should we continue to push students toward earlier and earlier specialization, or should we be teaching them to think more broadly?

The implications stretch far beyond the classroom. In a world that increasingly rewards narrow expertise, there’s a risk that we will lose sight of the benefits of general intelligence, skills like adaptability, problem-solving across different domains, and the ability to see the big picture. These are the very skills that once defined human progress.

Intelligence in a Fragmented World

Oberleiter’s findings suggest that the weakening of the positive manifold is not just an academic curiosity. It is a reflection of deeper societal trends that prize specialization over general cognitive growth. And while this may have short-term benefits, allowing people to become experts in their fields, it could lead to long-term challenges if we lose our ability to integrate knowledge across different domains.

In many ways, this research is a call to action. As we continue to advance technologically and socially, we must be mindful of the cognitive consequences. The Flynn effect was once seen as a marker of human progress, a sign that our minds were evolving in tandem with our societies. But now, as that effect falters, we must ask ourselves whether we are pushing our brains, and our children’s brains, in the right direction.

If we want to reverse the trend of the weakening positive manifold, we need to rethink how we value and cultivate intelligence. Specialization has its place, but so does generalism. It’s time to ask whether our educational and professional systems are preparing us for a world that needs both. Only then can we hope to build a future where intelligence continues to grow, not just in narrow domains, but in ways that connect and enrich all aspects of our lives.

I’m left pondering, this shift raises a troubling question: Is the fracturing of intelligence widening the gap between cognitive elites and those left behind? And more worryingly, does this fragmentation of intelligence exacerbate existing inequalities, or does it create entirely new ones?

While the Flynn effect may be fading, I do know, with the right attention to how we nurture our minds, we can ensure that our own intelligence remains a broad and powerful force, capable of rising to meet whatever challenges the future may hold.

Something else that I am sure of, intelligence is not a zero-sum game. We can build it, we just need focus and attention, and be decisive about what we read, do and learn.