Our Senses Have
Blind Spots
Here’s a hole in your eyesight that you’ve never noticed. Close your left eye, and stare at the cross with your right eye. Keep staring at the cross, and slowly move your face closer to the screen, then slowly back. At one distance, the dot will vanish!
💡 The Idea
Every eye has a blind spot. At the back of your eye, there is one place where the nerve that carries pictures to your brain leaves the eye. There is no room there for the cells that sense light, so that part of your eye can’t see at all. When the dot’s picture landed on that spot, it disappeared.
So why don’t you see a hole in the world all the time? Because your brain quietly fills it in with what it guesses should be there. Your brain hides its own blind spot from you!
Blind spots in attention
Our attention has blind spots too. In a famous experiment, people watched a video of players passing a basketball and counted the passes. Halfway through, a person in a gorilla suit walked through the middle of the game. About half the viewers never saw it! When we concentrate on one thing, we can miss something right in front of our eyes. Magicians call the art of steering your attention misdirection.
Blind spots in memory
Memory isn’t like a video recording. Each time we remember something, our brain rebuilds it, and it can leave out details or even add things that never happened. We can see an object thousands of times and still not really know what it looks like.
You don’t see everything,
and you don’t notice what you miss.
🔗 Where You’ve Seen It
- Activity 6: Ash From an Empty Hand
The holy man looked at his audience and talked, so their eyes followed his face, not his fingers. - Activity 7: Bending Spoons With Mind Power?
“Look at that!” In the moment when everyone looked away, the spoon was bent. - Activity 8: The “Mid-Brain” Mystery
The audience watched the cards, not the reader’s head tilting back to peep under the blindfold.
🌍 Use It Everywhere
This is why you should never cross a road while looking at a phone. Your eyes may be pointing at the traffic, but your attention isn’t, and you may simply not see a car.
It’s also why people who honestly describe the same event can tell different stories. When something important depends on what someone remembers, it’s worth checking in other ways too.
The coin challenge. Without looking, draw both sides of a coin that you use often, with every detail you can remember. Then get a real coin and compare. How many details did you get right?
Show the answer
Most people get many details wrong, or leave them out. In 1979, scientists in America asked people to draw a one-cent coin that they used every day, and most got many details wrong. We look at coins all the time, but we only notice what we need: their size and their number.
For parents and teachers
- The blind spot is where the optic nerve leaves the retina; there are no photoreceptors there. The test works best at a distance of roughly 25–40 cm from the screen, depending on screen size. It works on paper too, if you print this page.
- The gorilla experiment is by the psychologists Daniel Simons and Christopher Chabris. See “Bet You Didn’t Notice the Invisible Gorilla” (NPR). Children can find the original video by searching for “selective attention test”.
- The coin study: R. S. Nickerson and M. J. Adams, “Long-term memory for a common object”, Cognitive Psychology (1979).
- A note on witnesses: the point is not that people can’t be trusted, but that honest memory is imperfect. Encourage children to say “I think I saw…” and to welcome checking.
A Young Skeptics thinking tool, written with the assistance of AI tools, and reviewed by our editors. — CHARVAKA DESK