Why do people blink?
Studies show that, on average, people blink once every 2 to 10 seconds. We do this automatically because our eyelids protect our eyes from injury. Sometimes we blink intentionally, using what is called "sign language". For example, we may blink to get attention, inviting the other person to flirt. Sometimes we blink, expressing surprise, as if to say: "I can't believe my eyes!"
In humans, the inner surface of the upper and lower eyelids, as well as the eyes themselves, are lined with a thin, almost transparent membrane - the conjunctiva. The conjunctiva serves to moisten the surface of the eyes, since moisture is necessary for their proper movement. During blinking, the eyelid spreads moisture along the conjunctiva, and also directs it to the corners of the eye.