This figure looks as though
it's brighter in the center.
This one, made of the same pieces,
looks like it's brighter around the edges.
What's happening in these optical illusions by Akiyoshi Kitaoka? If you measured the actual amount of light given off by them, you'd discover the same amount of light is reaching your eye. It's just your brain that's interpreting that the top image is brighter.
But what's really strange is that your eye alone thinks the top one is brighter, too.
When light is bright, your eye constricts - by contracting or dilating your pupils - to protect itself from being damaged. Scientists used to think that this very fast reaction occurred completely as an automatic reflex, and that our higher brain wasn't used.
But our eyes will actually constrict as a reflex when they're looking at the top image, meaning that they constrict when the brighter light is only an illusion.
This means our eyes and brain are reacting to what we think we see rather than what's really there.
Researchers Bruno Laeng and Tor Endestad explain that their research shows that our brain and sensory organs react with each other much more than we realize.
They believe we create illusions because they help to protect ourselves from possible future events.
- This article is great science journalism: The illusion of light constricts pupils. Which of the figures below is brightest in the middle? Maybe when your brain plays tricks on you it isn’t a mistake, but rather a sort of improvement on reality. Science Nordic>>
Bright illusions reduce the eye's pupil. Bruno Laeng and Tor Endestad from the University of Oslo, Proceedings of the National Academy of Sciences of the United States of America>>
- Illusion of lightness, Akiyoshi Kitaoka, Ritsumei>>