Rats and people may rely on "metamemory" in a variety of different ways, scientists say. For a rat, it's likely about knowing whether you remember that predator in the distance; for people, knowing what we don't know helps us navigate social interactions.
Memory athletes like Sue Jin Yang — competing here in the 17th annual USA Memory Championship in New York City in 2014 — wear headphones to block out distractions as they memorize the order of decks of cards.
Carolyn Cole/LA Times via Getty Images
"My brain used to be my best friend," says Greg O'Brien, a journalist with early onset Alzheimer's. But he can't trust it anymore, he says. Alzheimer's is, in some ways, changing who he is.
Amanda Kowalski and Samantha Broun for NPR