Hermann Grid Illusion

How Many Black Dots Do You Count?

You may notice that the white dots in the Hermann Grid turn black as you look across the image. But look closely, there are only white dots!

The Science Behind The Illusion

There are a few different theories that try to explain why our eyes see the black dots in the Hermann Grid. These are some of the most popular ideas:

Theory # 1 - The retinal ganglion cell theory

Neurophysicists in the 1960's claimed that at the intersection of two lines, there are more areas blocked out, which is called ¨surround inhibition.¨ This may explain why you see the black dots at the intersections, and not in the straight line areas.

Many scientists do not agree with this theory because the dots, also called the illusory effect, that you see do not appear as strongly when you turn the image or change the shape of the lines.

Theory # 2 - Rod/Cone Interaction

This idea says that the reason you see the dots is because you can see it out of the corner of your eye, with your peripheral vision, where the rods and cones interact.

Theory # 3 - The light and dark effects our eyes

The illusory effect can be explained by the white area excites the focus of your eyes, while the dark area decreases the focus of your eyes.

More Examples

Works Cited

BrainDen.com - Disappearing Effect. (n.d.). Retrieved March 16, 2015, from http://brainden.com/disappearing-effect.htm

Cherry, K. (n.d.). 10 Cool Optical Illusions. Retrieved March 16, 2015, from http://psychology.about.com/od/sensationandperception/tp/cool-optical-illusions.htm

Hermann grid illusion. (n.d.). Retrieved March 16, 2015, from http://www.daviddarling.info/encyclopedia/H/Hermann_grid_illusion.html

Schiller, P. H., & Carvey, C. E. (2005, 12). The Hermann grid illusion revisited. Perception, 34(11), 1375-1397. doi: 10.1068/p5447

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