The unnoticed eye motions that help us see the world

Neuroscience

27 July 2021

Eye movements lasting only a few hundredths of a second create an information-laden ‘smear’ on the retina.

When we look at a scene, our eyes dart from one point to another an estimated three times per second. Although we don’t perceive this rapid-fire jitter, experiments reveal that it produces visual information that helps us to make sense of the world around us.

To see in sharp detail, a person’s eyes frequently shift to focus on objects in their peripheral vision. These extremely rapid eye movements create ‘motion streaks’, visual smears on the back of the eye. A motion streak stretches from an object’s starting position on the retina to its position after eye movement.

Richard Schweitzer and Martin Rolfs at the Humboldt University of Berlin showed six differently patterned objects to volunteers and asked them to focus on one object. While the volunteers’ eyes were moving towards that target, the objects’ positions changed. The researchers then overlaid all of the objects with the same pattern to make them indistinguishable.

Participants successfully found the target in most cases, but were more likely to do so if its movement had generated a motion streak. This suggests that information gleaned from the streaks helps our jittering eyes to keep track of where objects are.