Seeing clockwise spirals that induced an expanding motion after-effect enabled participants of a recent study to read letters at smaller font sizes.
Washington DC: A recent study has found that exposure to a common visual illusion may enhance your ability to read fine print. Visual acuity is normally thought to be dictated by the shape and condition of the eye but these new findings suggest that it may also be influenced by perceptual processes in the brain. Interest in the intersection between perception and reality led Lages and co-authors Stephanie C Boyle (University of Glasgow) and Rob Jenkins (University of York) to wonder about visual illusions and how they might affect visual acuity.
To find out, the researchers employed a tool that can be found in any optometrist’s office: the classic logMAR eye chart. On this chart, letters are arranged in rows and the letters become increasingly smaller and more difficult to read as you move down the chart. Optometrists calculate visual acuity based on the size at which a person can no longer reliably identify the letters.
The experiment revealed that participants’ visual acuity differed depending on which spiral they saw. Participants who started with normal visual acuity and saw clockwise spirals–which induce adaptation to contracting motion and cause subsequent static images appear as if they are expanding–showed improved visual acuity. That is, they were able to identify letters at smaller font sizes after exposure to the clockwise spiral.
Those who saw counter clockwise spirals–which induce adaptation to expanding motion and cause later images to appear as if they are contracting–actually performed worse after exposure to the spirals. A third experiment, in which each participant saw both types of spirals over two sessions, showed similar results: Seeing clockwise spirals that induced an expanding motion after-effect enabled participants to read letters at smaller font sizes.
But don’t throw out your eyeglasses just yet: The researchers note that the overall boost to visual acuity is small and fleeting. Nonetheless, this common visual illusion reveals a fundamental aspect of how we see, showing us that our ability to discriminate fine detail isn’t solely governed by the optics of our eyes but can also be shaped by perceptual processes in the brain.