MICHAEL MOSLEY: The test that reveals Covid has made us more stupid... and what ... trends now
Are we becoming slower-witted? The answer should worry all of us.
A few years ago I made a TV programme called The Great British Intelligence Test where we measured the brainpower of the nation and carried out the largest intelligence experiment of its kind.
More than a quarter of a million people took our special IQ Test, developed for us by scientists from the Department of Brain Sciences at Imperial College London. (You can see what we put people through by searching online for ‘Michael Mosley IQ test’.)
We discovered, unsurprisingly, that when it came to problem-solving, people in their early 20s did the best; they have more knowledge on their side than, say, a teenager, but their brains are also working faster than people who are middle-aged or older.
The reason problem-solving ability falls with age is, in part, linked to how well insulated the connections are between your brain cells.
Dr Michael Mosley made a TV programme called The Great British Intelligence Test
As we age, the myelin sheath that surrounds the brain’s wiring gets thinner and communication between our neurons slows. Our brains quite literally slow down.
But there was some good news for older people; while other cognitive skills decline with age, verbal ability increased, peaking in people in their 70s. Oddly enough, cat lovers scored higher on verbal ability than dog lovers (though that may have been chance), as did book readers and people who are fond of fruit and veg.
But the biggest surprise came much later, long after the programme had aired on TV.
That’s because the test was put online in 2019, before the Covid pandemic swept the world, and the researchers continued to collect data well into 2020, when the outbreak was at its worst.
By this point they’d included questions about whether people had had Covid and, if so, how it had affected them.
They found that people who had been infected scored lower on the IQ tests, particularly when it came to something called executive function, a measure of mental skills such as memory, flexible thinking and self-control. If your executive function is affected, this can make it hard to focus, follow directions and handle emotions.
The team have since completed a larger study involving more than 112,000 people, which was published last month in the New England Journal of Medicine.
This confirmed the long-term impact that Covid can have on our brains. People who had a mild infection lost a couple of IQ points, but those who developed long Covid saw an average fall in IQ of about six points.
And the results of this study fit in with another more worrying trend, which is that IQ scores have been falling worldwide since the 1970s. In a 2018 study published in Proceedings of the National Academy of Sciences, researchers looked at the IQ scores of young men in Norway, recorded when they were conscripted for compulsory military duty. Over a 40-year period, beginning in 1970, there was a steady decline of about seven points per generation.
This phenomenon has since been recognised in other countries, including the U.S. and the UK.
While no one really knows exactly what’s going on, there’s a suggestion that it could be to do with rising levels of obesity and our growing reliance on ultra-processed food, both of which are bad for the brain.
Being struck down by an infectious disease, particularly one that persists (like Covid), is also a surefire way to reduce your IQ score.
There is also a growing concern, among some researchers I’ve spoken to, that the rise in artificial intelligence will add to downward pressure on human intelligence, as we increasingly rely on machines to do our
