Peripheral Vision: Mapping Color onto Shape

It's well established in vision science that perception of shape and color declines precipitously outside the central one or two degrees of visual arc (about the size of your thumbnail held at arm's length). Most people find it surprising, actually, how poor their peripheral vision is, and how narrow the region of clarity (despite the number of hours each of us has logged expertly seeing outward things). Dennett's playing card experiment is a nice way to test yourself: Take a playing card from a normal deck, without looking at it. Hold it at arm's length to one side, just beyond the field of view. Keeping your eyes fixed on a single point ahead of you, slowly rotate the card toward the center, noting when you can discern its color, its suit, and its value. It won't be until almost dead center that you'll be able to tell if it's a Jack or a King.

But if shape and color perception are bad individually in the periphery, Peter Neri and Dennis M. Levi (2006) suggest that things are even worse when you combine them.

Suppose you are presented a red square and a blue circle. Regions of your brain specializing in color will register a red thing and a blue thing. Other regions specializing in shape will register a square and a circle. If everything works right, you'll also know that it's the square that's red and the circle that's blue -- but that is a bit of extra work, an additional thing that must go right. In some situations, people will get the colors and shapes right, but they won't know which color went with which shape (Triesman and Schmidt 1982).

Neri and Levi's experiments suggest that this sort of "feature binding" goes especially badly in the periphery. Even at resolutions where their subjects could make out color and shape individually, they could not accurately put those colors and shapes together.

Now I have some picky complaints about the methodology of their experiment -- having to do with Gestalt principles for shape detection and possible single-feature computing shortcuts (if you go to their article, note the "7"-like figure in the left hand image in Fig. 1C which could not occur in a non-target image; HT: Ryan Robart) -- but there's also the phenomenological question. Peripheral vision seems blurry, and the color of unknown objects can be surprisingly indistinct or inaccurate, but does it additionally seem on introspection that the colors out there get mapped onto the wrong objects, or that the colors and shapes don't coherently fit together?

Billock and Tsou (2003) describe the phenomenology of binding failure thus:

In other cases, all sense of object and surface can be lost and the target is perceived as a ‘jumble of lines’ or ‘extremely confusing and hard to describe’. Moreover, the contrast of equiluminant images can seem unstable – Gregory describes such images as ‘jazzy’. In 1927, Liebmann reported that there is a ‘critical zone [where] everything flows…glimmers…most everything is soft, jelly-like, colloidal. Often…parts which belong together in the normal figure now have nothing to do with one another. [It is] a world without firm things, without solidity.’

Is that how peripheral vision seems? I've been walking around today trying to notice, and it just doesn't strike me that way. Indistinct, yes. But binding failure is different.

Furthermore, I've finally found a use for all those silly business cards they gave me when I was promoted to Associate Professor. On the backs, I've written letters and shapes right next to each other in arbitrary colors. I made about 80 cards, each holding two of eight shapes in two of four possible colors. Rotating them in from the periphery, I don't find myself making many binding errors. As soon as the cards are clear enough to distinguish shape and color, I know which shape goes with which color.