This week I’m attending the annual meeting of the Vision Sciences Society in Naples Florida. Every day or so, I’ll post about a subset of the cool, interesting, funny, or quirky (I won’t say which) talks/posters I happened to catch. You can read the first installments here.
This morning had a great new color illusion/demo presented in a talk by Jordan Suchow and George Alvarez entitled “Silent updating: Cross-dimensional change suppression.” The effect is pretty similar to one presented by Jun Saiki and Alex Holcombe a couple years ago at Vision Sciences (“Surface-based, unpaired feature representations mediate detection of change to feature pairings”), but this one was a particularly dramatic demonstration.
If you show people a dot that continuously cycles through all the colors in the spectrum, you can see it changing systematically. If you arrange 300 such dots in a thick ring around the center of the display (imagine Saturn and one of its rings) and you maintain your gaze at the center of the display (e.g., on Saturn), you can see all of the colors flickering and changing. But, if you start the entire ring rotating around where you’re looking, all the color-changing appears to halt. The effect is dramatic, and Suchow and Alvarez generate several possible explanations for it. They argue that people are silently updating the colors of the objects in the ring so that if the display halts and suddenly reverts to the original colors, people notice. I didn’t find that explanation particularly compelling — it’s unlikely people can update all of the individual colors simultaneously, and reverting to the original colors will produce a big luminance signal. My bet is that they store little if anything about the colors, but they are really good at seeing motion. The explanation I prefer is one suggested by a questioner in the talk: The rotation of the entire ring produces a big motion signal for the visual system, and that signal masks the smaller changes of the individual dots. That principle–big motions hide smaller ones–is used in magic as well. A big arm movement can hide a subtle change to something held in your hand.