The coupling of motion and direction is based partially on the objects’ synchronicity in time (and speed). Physiologists have proposed that such perceptual groupings may arise when there is synchronization of nerve impulses that are evoked in multiple brain regions by the individual quartets or ballerinas. If so, what happens if ballerinas in different parts of the visual field spin at speeds slightly different from one another? Would they still get synchronized? What if ballerinas were of nonuniform sizes? Could you uncouple large and small ones then? Have fun!

Note: This article was originally printed with the title, "The Power of Symmertry".

3 Comments

1. 1. Ellipsoid 11:30 AM 5/1/09

   I find that I can easily flip the direction of the dancer by looking at her shadow. Is this because my brain applies the "clockwiseness" of the clockwise dancer to the counterclockwise shadow, thus flipping the spin of the whole shebang?

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2. 2. Cristi Stoica 06:38 AM 5/3/09

   In
   http://www.unitaryflow.com/2008/10/spinning-dancers-mistery.html
   it is explained with animated images why the "spinning dancer" is perceived by most of us as spinning clockwise.
   
   It is then showed why the laws of perspective indicate that she really spins counter-clockwise.

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3. 3. Dolmance 01:42 PM 5/24/09

   Poor Bobby Jindal.

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