Does it look like a star-burst on the corners?
What this illusion illustrates is that although it looks like there is an “airbrushed” star-burst (white lines extending from the center of the star to the corners) it is of course an OPTICAL ILLUSION! What I’ve actually done here is created a series of stars and placed them on top of each other. With a slight gradient change in each successive layer.
This illusion also works with squares, but for squares you only see the light star-burst effect. It was called Vasarely’s nested squares illusion. But when you try the illusion with a star, you also get the darkened shadow effect where it gives depth to the illusion. This is referred to as “Corner Angle Salience Variation”. Don’t look for that term on Jeopardy! anytime soon.
Perhaps the evolutionary reason for this is a fluke in our eye balls! The ganglion cells in the eye that compute the shade of a specific area have to relay that information to the brain. And while they relay the information to the brain, they do some extrapolating and that’s where it gets confusing!