Even if you don’t fidget or yawn,
may give you away
In the Blink of an Eye
By John A. Stern
THE EYE, our most delicate sensory equipment, is surprisingly vulnerable. To be sure, much of it is protected by the skull: the socket, composed of a bony cavity padded with fat, absorbs all but most severe affronts. But roughly one-tenth of the eye’s total surface—the almost-shaped portion that peers out into the world and gathers light—has, when open, nothing between it and the atmosphere.
The body protects this vital asset by blinking. During the blink itself, which may last no longer than a tenth of a second, a flap of one of the body’s thinnest skins, reinforced with tough cartilage-like fibers, snaps shut. Then the lids retract, coating the eyes in a film of tears. These tears rinse away debris and cleanse and lubricate the surface.
Blinks can take several forms. Besides the blinks that wash the eye, there are those associated with unexpected circumstances (such as loud noises), as well as the voluntary flaps of the eyelids that may express anger or incredulity. Another type, the spontaneous eye blink, is neither voluntary nor reflexive. Most blinks are spontaneous.
Mere eye-rinsing requires a blink no more than once a minute; yet most people blink around 15 times a minute. Why do we blink so frequently? Apparently there is a direct relationship between spontaneous blinking and the mind. Using cameras, infrared lights and electrodes to gauge the electrical bursts from nerves and muscles around the eyes, scientists can now discern how the frequency and duration of blinks vary according to whether a person is alert, bored, anxious or concentrating.
Studies show first of all that we blink less when we’re most alert. A person reading a novel blinks about six times a minute; someone engaged in conversation blinks more than twice as often. Automobile drivers blink less when negotiating distracting city streets than when cruising down highways. When a driver is passing another vehicle, his blink nearly always decrease as his eyes shift from the road to the speedometer or rear-view mirror and back.
A more subtle effect on blinking seems to occur when a person is bored. During one experiment that required people to listen to a 32-minute series of tones, the fraction of a second that their eyes were shut during blinks grew by more than 30 percent. Apparently when the brain judges incoming information to be less than compelling, it allows itself to rest, and blinks last longer.
Researchers have learned that the rate and duration of our blinks vary according to the tasks we perform. People engaged in visual activities like drawing blink less frequently; fatigued individuals blink more often than when they are rested. We blink more if upset.
Anxiety also increases the number of blinks. Novice helicopter pilots blink more often than instructors, and witnesses under cross-examination blink more frequently than those facing friendly lawyers. When a person answering a question has to face another person—rather than an inanimate object—during his response, blinking increases. And when such a subject faces someone who asks uncomfortable questions requiring direct yes or no answers, blinking rates rise still higher.
This connection between blinking and apprehension explains why television newscasters are instructed to blink normally, in order to appear calm and controlled—and, thus unflappable—before the cameras. This also applies to politicians. Neuropsychologist Joe Tecce’s studies indicate that anxiety and tension increase the frequency of blinking. So far, though, psychologists have no explanation of why.
The relationship between memorizing and blinking seems clearer. Subjects asked to commit series of letters to be stored. The more letters the subjects are asked to be memorize, the more time elapses until the blink: the brain needs more time to store six characters than it does two. It seems likely, then, that a blink indicates the moment at which the memory forms and the brain anticipates no additional material.
A similar pattern occurs during reading. People are most likely to blink as their eyes reach the end of a line, or when they fail to understand it and reread the three or four previous words. The brain seems to need to pause between significant sensory episodes; the blink marks the pause.
Blinking, then, serves as a kind of mental punctuation. A blink seems to occur at the moment we stop taking in information and start thinking about it. The brief, infrequent blinks of city drivers are like commas, dividing the images speeding before their eyes into manageable units. When blinks last longer and arrive more frequently, during the formation of memories or making decisions, they are more like periods, allowing the brain briefly to store or mull over information.
This may explain the curious fact that the same task triggers different rates of blinking in different individuals. Arithmetic puzzles, for example, cause most people to blink more, but some less. A person who formulates the answer visually, imagining the numbers in his mind’s eye, will seldom blink, in an attempt to freeze the picture. Another person’s blinking rate may rise during the exercise, because his brain is ordering a blink at the end of every stage of problem solving. The differences in how we each think, in other words, may be reflected in how we blink.
*John A. Stern is chairman of the psychology department at Washington University in St. Louis.
CONDENSED FROM THE SCIENCES (NOVEMBER/DECEMBER ’88), ©1988 BY THE NEW YORK ACADEMY OF SCIENCES, NEW YORK, N.Y.