Oh noes, your brain is short-circuiting! :P
I can only see clockwise, and I can't make myself see it spinning the other way.

If you want to see how they did it, save and open the dancer image in a .gif animation program. It's composed of 35 images altogether, and each of them has a shadow effect to imply 2 different leg and arm positions. When I watch the animation she appears to have her right leg extended and be turning CW except for 2 or 3 intervals when she changes to CCW for an instant. It's an interesting optical illusion, but I don't know about the brain stuff. That seems pretty oversimplified.

BTW, the Coriolis force does not change the direction of small amounts of swirling water relative to the equator, but it does impact large scale motions such as wind. Hurricanes -- yes, toilets -- no.

Geoffrey - you STILL haven't seen it go the other way? (assuming you've been looking at it all day like I have) :P I mainly see it clockwise, but definitely see it both ways.

TFMH - I thought about doing that but I don't have a GIF animator at the moment. Plus I like the way it messes with my head and didn't want to risk having that go away by understanding too much about the mechanics. :)

As for the Coriolis force, it does TOO impact toilets ... don't you watch the Simpson's, for crying out loud??!!??!!

No, I guess my brain is righty, although I took the http://similarminds.com/personality_tests.html RL brain test, and I was more right-brained, left was pretty close.

mmmmmmmmmm raisins...

I'm able to switch it myself. That's pretty cool. ...not as cool as the raisins, but pretty cool.

Isabel from God Plays Dice said some cool stuff about it too. I'll paste it below and act like she was commenting in my blog instead of just posting in her own :P :

There is a woman spinning; the question is, is she spinning clockwise or counterclockwise? Supposedly this has something to do with which side of the brain you use, although I'm not sure I buy it.

But my first thought was "clockwise from whose perspective? From the perspective of someone looking from above, or from below?" (To clarify what I mean by "clockwise", I mean that the dancer is turning to her own right.) I think this does say something about my brain, namely that I demand precise definitions for terms, at least for the sorts of terms that can have them.

Some of the commenters at various places say that you have to look at the shadow, because the shadow doesn't agree with the dancer; as far as I can tell this isn't true, and this is not some sort of optical illusion.

The actual resolution is that you can imagine reflecting the dancer through the plane of your monitor (I almost said "the plane of the board", because usually when I'm thinking about three-dimensional pictures it's when I'm teaching calculus), which will change the direction of rotation but not the picture. So on an intellectual level I understand why both perceptions must be possible. But I can't see her going counterclockwise. Not at all.

i was mesmerized by the... uh... other... uh.... how can i make her stop spinning? and is she single?

i generally see her going clockwise (clockwise if one were looking from above, down at her head). although i eventually learned i can get her to switch directions by staring lasciviously at specific body parts for awhile. don't ask how i learned that.

does that mean left-brained people are lechers?

TFMH - I found someone that took a lot of time to undersimplify an explanation about just how over simplified those comments were - http://www.theness.com/neurologicablog/index.php?p=27

Terry - I'm glad you, uh, like her. Er something. No really though, I can't get past the word "lecher". That is the most hysterical thing for some reason. I need to try to work it into my everyday vocabulary.

Nuje - Nuje. ::sigh:: Must you *be* such a lecher??

Tee-hee!

What does it mean that when I found the man in the coffee beans (in about 3-5 secs) I actually was startled? Like "Eek, there's a disembodied head in these coffee beans" kind of startled. Even though I was looking, as per the instructions, for what I found?

Oh, that's easy ... it means that you had the exact same response as I did in the exact same amount of time.

Plus I think this kind of goes along with what the guy that wrote that article was saying - since they didn't give clear enough instructions on exactly what we were to be looking for, the responses our brains will have to this exercise will be too varied to really determine anything.

...

I bet his head smells good though ...
:D

Hey, yeah -- it probably does!

. . . could we sell coffee shampoo?