Your mind can play tricks on you, Richard

In this one, though the lines are parallel, the placement of the triangle fools you into thinking they're bending, making your mind over compensate.


The straight lines here make you believe that isn't a perfect circle, again forcing your brain to really struggle with the truth

And in this pic your brain just cannot comprehend there is no 'i' as a second letter - look again - there really are only 3 letters! The brain is truly a wonderous organ.

Thanks to the fantastic Oriental Sweetlips for this corking picture.