The ever brilliant Richard Wiseman strikes again. This is without a doubt the most persistent illusion I've ever seen. Click on the image and it will get larger.
My brain is so determined to see spirals that even when I trace what are clearly circles, I perceive a spiral. I don't know about you guys but I cannot force myself to see these circles. Man! These spirals that aren't spirals won't go away.
Human brains are pattern recognizing machines. I say that all the time. As such, the need to see a pattern can override reality without a whole lot of prodding. I'd love a real explanation of this particular illusion from a physiological perspective. Seriously. What structures in my brain are overriding what my eyes see? Wild stuff!