That’s why we blink

An experiment proves it: we don’t just blink to lubricate the eyeball; it is also done to improve vision – it intensifies contrast sensitivity. Enough to look differently at this small, automatic, systematic body movement, which takes up 10% of our waking time without us realizing it.

Hervé Poirier, editor-in-chief of the scientific magazine Epsiloon, explains to us today that we have understood why we blink so much…

franceinfo: Explain to us Hervé, we believed that blinking was only necessary for the lubrication of the eyeball?

Hervé Poirier: The experiment was carried out in an American laboratory. Volunteers look at images made up of very small oblique stripes, white and black, and say whether they seem inclined to the left or to the right. And they must blink, either during the observation or just before.

Result: their success increases significantly if the eyelids blink during observation, whether reflexively or voluntarily. Contrary to what we thought, blinking actually plays a role in the processing of visual information.

We close our eyes to see better, is that a bit contradictory?

Until now, we thought that we blinked to lubricate the eyeball – a kind of harmless mechanical maintenance. Most often, we do not realize it, because our brain reconstructs the obliterated scene.

However, we suspected that there must be something else, because we blink more often than necessary at this lubrication. Blinks can repeat up to 20 times per minute, and last up to 300 milliseconds : overall, we spend up to 10% of our waking time with our eyes closed.

With this experience, we understand better why. High-resolution eye tracking shows that blinking shortens the time of exposure to the stimulus by 15%. But, according to the spectral analysis of visual signals, the luminance modulations produced by this blink increase the power of incoming signals by more than 20% when the eyelid reopens. In short, by blinking, we see for less time, but we see better.

What exactly happens when you blink?

Retinal neurons are highly sensitive to changes in brightness. Closing, then opening the eyelids modulates their activity, which intensifies their sensitivity to contrasts, and improves the perception of the overall structure of the visual scene. In other words, blinking wakes up the eyes.

We already knew that our brain tries not to blink at the wrong time, so as not to miss important information. We now need to know if our brain controls this small body movement, to focus precisely on strategic moments. Not impossible, because our body is a marvelous machine, with unsuspected unconscious resources.