Friday, October 26, 2007

Left brain vs right brain

Click to get a more economical page with the animation.

Is she rotating clockwise or counter-clockwise?

If clockwise, your right hemisphere is more active which makes you oriented towards big picture, fantasy, religion, philosophy, spatial perception, and risk taking.

If counter-clockwise, as most people, your left hemisphere is more active which makes you oriented towards details, logic, words, order and pattern perception, strategy forming, practicality, and safety.

Your humble correspondent is so hopelessly clockwise that he was unable to see her rotate in the opposite direction after five minutes of attempts. ;-) It took me one more minute to prove that it is actually possible that the leftists can see the opposite direction of motion.

Why are both interpretations possible? Well, if the two-dimensional picture can be seen as a projection of some three-dimensional scene S, then you can create a mirror image of the three-dimensional scene, S', by changing (x,y,z) to (x,y,-z) where "z" is perpendicular to your screen. The rotation in S and S' have the opposite directions to each other.

Update: I have changed my mind. The leftists who see her rotating counter-clockwise are clearly deviants. Here's a proof. Look at the two screenshots above. On the left picture, you see that the leg on the right side is shorter than the other one. Why is it shorter? It is because it is more closely aligned with the direction where you look: it goes behind the screen, at least assuming that your eyes are not below the height of her buttocks. It follows that on the left picture, you can't see her face.

On the other hand, you see that both legs are comparably long on the right picture. It is because you can see her face and the flying leg is pointing in front of the screen. The angle between the photons coming from her knees to your eyes and the direction of her leg is almost independent of what leg you choose. This is the interpretation that the clockwise rightwingers offer: the right picture includes her face when colors are added. The leftists have the opposite interpretation - they think that they can see the face on the left picture not the right picture - which is wrong. And the arguments about the (x,y,z) and (x,y,-z) mirror images above don't work once you take perspective into account. If you realize that you're looking at the beauty from a height above her buttocks and it is thus not a parallel projection, the symmetry between the two cases (or between S and S') disappears, the rightists are shown to be correctly evaluating the picture and the leftists are proven, once again, to be a majority (?) of charlatans. ;-)

And that's the memo.

Hat tip: Yorick


  1. I'm hopelessly clockwise as well. I had a hard time reconciling that there seem to be so many of us who are otherwise rational (and I choose that carefully instead of logical) who are showing up right-brain. I think that what we are seeing is how intuitive someone is. Or it could be simply how good your brain is at ignoring the red herring in the illusion.

  2. Sorry, phelps, look at the original article - do you agree that you made a typo? Clockwise means right-brain, doesn't it? ;-)

    The article states that clockwise people are using the right hemisphere more than the left which I suppose is referred to as "right brain" later in the article.

  3. Since the viewing angle appears to be nominally at eye level, the foot of the outstretched leg makes an ellipse on the the screen. Since the lower portion of the ellipse is going from right to left, this is a projection of an object rotating clockwise. That she is also oscillating up and down merely places the ellipse at a slight angle to horizontal.

  4. I'm wondering what you are talking about? I see her changing direction when she gets giddy. I'm doing a mini survey my scientist daughter sees clockwise I'm waiting to see what my artist daughter has to say.

  5. Well, well, well. She's dancing on the mirror (or at least polished surface), isn't she ? Then look closely at the point in the mirror she touches by her heel. The way we see the reflection proves that we're looking from the bottom (our eyes are almost on the floor). Thats why left-brained are right. :)) :p
    BTW looking at this point is the easiest way how to force her to rotate counter-clockwise (at least for me:)