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.
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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