Gazing At This Optical Illusion Can Actually Sharpen Your Vision


Tom Hale


Tom Hale

Senior Journalist

Tom is a writer in London with a Master's degree in Journalism whose editorial work covers anything from health and the environment to technology and archaeology.

Senior Journalist

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Optical illusions aren’t just good for giving you a headache and fuzzy eyes.

Researchers from the University of Glasgow and the University of York in the UK have carried out research that indicates regular exposure to a certain optical illusion helps enhance people’s ability to read small text. The study was published in Psychological Science.


"We discovered that visual acuity – the ability to see fine detail – can be enhanced by an illusion known as the 'expanding motion aftereffect' – while under its spell, viewers can read letters that are too small for them to read normally," study author Martin Lages of the University of Glasgow said in a statement.

To investigate the effect of the optical illusion, the researchers tested the visual acuity of 74 participants using a logMAR chart, the classic eye chart you see in your optician's room where the letters get smaller on each row. The team then showed them an optical illusion of a spiral that either rotates clockwise or counterclockwise for 30 seconds, shortly after which they were given another visual acuity test.

Those that watched the clockwise rotating spiral (which gives the impression that images are moving towards you) experienced a brief period of better visual acuity, meaning they were able to see smaller letter sizes after looking at the clockwise spiral. Those who viewed the counterclockwise spiral experienced the opposite.

"We were pretty impressed by the consistency of the effect. No matter how you break it down – by letter size, by letter position – the performance boost is there," added Rob Jenkins of the University of York. "And there was a correlation with initial ability: The harder people found the task, the more the illusion helped them."


However, these effects were short lived and vision returned to normal pretty promptly.

So what can explain this strange phenomenon? In the study's conclusion, the researchers write: "A possible explanation is that the expanding motion aftereffect did not alter the neural representation but facilitated the “readout” or recognition of letters. The contracting motion aftereffect may have increased foveal crowding, whereas the expanding motion aftereffect may have released crowding between letters."

Although the experiment might seem like a bit of fun, it actually reveals some deeper truths. While many may think visual acuity is dictated solely by the physical shape and condition of the eye, this study adds to research that suggests it is also influenced by perceptual processes in the brain.


  • tag
  • brain,

  • eyes,

  • optical illusion,

  • perception,

  • eyesight,

  • vision illusion