Anomalous figures and the tendency to continuation
I found this article while browsing comments on Joi Ito's article about Letter Ordering. The article talks about a interesting trick our minds plays on us when we are looking at images and expect some kind of continuation to occur and it doesn't.

I specially like this one. You can clearly imagine the triangle on this one (you can't even imagine it without the triangle) although there is just a few information to support its existence:

Minguzzi G. F. (1986). Anomalous figures and the tendency to continuation. This happens when it is "evident" in some way that the region which may be thought of as performing the function of covering the underlying continuation of inducing figure has the quality of a solid surfaceFor instance check how the left image makes you think there is a circle between the thicker lines while the right image doesn't:

I specially like this one. You can clearly imagine the triangle on this one (you can't even imagine it without the triangle) although there is just a few information to support its existence:
