If you don’t keep your body and brain active, senility sets in, even if you’re a little kid. The circulation in your brain gradually decreases. Like the cat in that experiment—by the time he lost interest in eating, the blood in his brain was just barely moving. It’s the stress that does it. Human beings have thought up everything from hunting in groups to pop songs and car races so our brains wouldn’t atrophy, but there aren’t that many genuinely effective ways to guard against senility nowadays.
