Some 2.3 million of U.S. adults older than 65 — more than 4% — have a diagnosis of dementia. But even without a diagnosis, a certain amount of cognitive decline is normal as age sets in.

Since the first TV game show—the BBC's "Spelling Bee"—aired in 1938, these programs have captivated audiences.

Mindset check: we've all been stuck, feeling like we can’t improve. But here’s the secret—your brain is a hidden superhero, ...