Why do we blink?

People blink mainly to moisten their eyes, but there's a lot more to blinking than, well, meets the eye. John Stern, a professor at Washington University in St. Louis, Mo., has studied blinking and learned some interesting stuff: Infants blink about once every minute, but older people blink 10 to 15 times a minute. And a person's blinking rate decreases when a person is concentrating on something (like threading a needle) and it increases when a person is tired or under stress.