Which Way Is the Dancer Spinning?

Courtesy of Marginal Revolution, take a look at this dancer. Is she spinning clockwise or counter-clockwise?

For me there is no question: the answer is clockwise. For my wife, the image is without question spinning counter-clockwise. Our babysitter, April, sometimes sees her clockwise and sometimes the opposite. This little dancer offers a powerful lesson regarding how things we conceive as incontrovertible facts are often highly subjective.

Just for fun, list your college major, your occupation, and which way the dancer spins for you. We’ll tally the data and see what we find.

We will give a piece of Freakonomics schwag to one randomly chosen person among the first two hundred commenters who provide the correct data.

And separately, how did someone invent this dancer? How did they figure out that some people would see her spin one way and others would see the opposite? If you know the answer to this question, please tell us and we’ll also offer you schwag.