Why do we blink?

We do it to keep our eyes moist and to wash away irritants such as dust and dirt. Each blink brings liquid secreted by the tear glands into contact with the surface of the eyeball. An adult blinks roughly once every five seconds, but tests have shown that we blink less when undertaking tasks that demand our attention, such as reading. Very young children also seem to blink less - just once or twice per minute.