Here’s how old you are when your cognitive skills peak

Forget everything you’ve heard about mental decline starting in your thirties. A new study suggests your brain may keep getting sharper well into your forties, allowing for a much higher cognitive skill peak, but only if you keep it engaged.

Researchers from Stanford and the University of Cambridge followed thousands of German adults over several years. They tracked how each individual’s literacy and numeracy skills changed. However, instead of comparing different age groups all at once—a...