When I was in my late twenties, I remember reading a pop science article which told me that I had already passed my cognitive peak. I had barely started my career and already my brain was apparently on an inexorable downward slope.

I shrugged it off at the time, but as I enter my forties, I find the idea more depressing. How many years before people begin to tell me encouragingly that what I lack in cognitive skill I make up for in “wisdom”? Am I going to have to start doing crosswords to slow my inevitable decline?

Not necessarily. A new longitudinal study has painted a very different picture of what happens to people’s cognitive skills as they age. The OECD runs a programme in which it tests the literacy and numeracy skills of adults aged 16 to 65 across 39 countries. Germany, uniquely, retested a panel of participants three-and-a-half years later.