We blink about 10-40 times per minute. Almost all mammals blink and the rate is variable. For humans, the conventional mechanical explanation given for blinking is that we need to moisten our eyes, clean the debris from the eye and refresh the eyes. Obviously, having a eyelid in front of the eye can also prevent against damage if your eyelids respond to the potential threat. But, these are just mechanical reasons. There is another hypothesis that links the attention state with blinking. For example it is known that when we need to acquire information, say watching an interesting part in a movie, we decrease our blinking rate. There have been other hypotheses linking our emotional state to blinking too.
Now for three not so obvious reasons, discussed in science but not found in common literature:
- 1.There appears to be a link between dopamine levels and blink rate. In Parkinson’s disease with lower blink dopamine levels the blink rate has also been shown to be decreased. Whether there is a casual link needs to be determined but this could be good marker of brain hormones.
- 2.Brain processing is also known to be paused during the blink from attention to a default mode network “idle” mode. This is not something that can be induced by watching noise or other smallish stimuli. The blink is executed to take a break from the processing task.
- 3.There is a voltage difference between the cornea (front of the eye) and retina (back of the eye). It has been hypothesized that eyelids work as conductors to neutralize the potential with the surface of the body. Thus the blink will also neutralize any potentials generated on eye movement too. Does it matter? It is unknown at the moment.