“There are three types of mathematicians, those who can count and those who can’t.”
Bad joke? You bet. But what makes this amusing is that the joke is triggered by our perception of a paradox, a breakdown in mathematical logic that activates regions of the brain located in the right prefrontal cortex. These regions are sensitive to the perception of causality and alert us to situations that are suspect or fishy — possible sources of danger where a situation just doesn’t seem to add up.
Many of the famous etchings by the artist M.C. Escher activate a similar response because they depict scenes that violate causality. His famous “Waterfall” shows a water wheel powered by water pouring down from a wooden flume. The water turns the wheel, and is redirected uphill back to the mouth of the flume, where it can once again pour over the wheel, in an endless cycle. The drawing shows us a situation that violates pretty much every law of physics on the books, and our brain perceives this logical oddity as amusing — a visual joke.