A piece in today’s Guardian (“The Science Behind the Dress Colour Illusion“) quotes me as a primary source, but the exigencies of copy deadlines mean that in a few places my intended meaning was lost. Here are my (unedited) notes on the matter, which should clarify my comments in the Guardian article that might have left more than a few people scratching their heads:
What’s striking about this is not (just) the illusion itself (there are many examples of how context can affect our colour judgements), but the sharp social disagreement on this issue. Most people fall into one of two camps, with each side being sure they are right and the other side wrong, to such an extent that many cannot see it as an illusion at all: the dress simply is the colour it seems to them, and anyone who says differently is either having a laugh or can’t see colours properly. Here at the Sackler Centre for Consciousness Science, according to an unscientific straw poll conducted by my colleague Jim Parkinson this afternoon, we actually divided equally into three camps: black/blue, white/gold, and brown-gold/blue. But stick to the dispute between the first two camps: what’s going on?
Most illusions have the form: things seem one way, but this can be shown to be at odds with the way things objectively are (e.g., the length of the lines in the Müller-Lyer illusion, or the sameness of the reflectance properties of the two tiles in the checker shadow illusion). But with the dress illusion, things are different. As things stand now, we only have the picture of the dress, the two groups of people with their different experiences of the dress’s colour, and the assurances (of some people) that despite the dress looking white and gold (to some people), it actually is blue and black. If a white-and-golder asks how this could possibly be the case, they are just referred to a different picture, which looks blue and black to everyone, and are told that the second picture is of the same dress as the first picture. Unsuprisingly, this is not persuasive to the white-and-gold crowd: How *could* it be a picture of the same dress? Do you mean the same style of dress, but in a different colour? Etc. Imagine how it would be for the checker shadow illusion if one only saw the first of the three images in the Wikipedia entry (http://en.wikipedia.org/wiki/Checker_shadow_illusion), and not the other two images which demonstrate that the reflectance properties of the tiles were the same. When confronted with scientists’ claims that despite appearances, the tiles are of the same colour, one would just say “rubbish!” and go about one’s business.
So the first step in reaching a truce in the “dress wars” is to construct a demonstration that can show to the white-and-gold crowd how the very same dress can also look blue and black under different conditions.
(A good first step is with this image my Sackler colleague, Keisuke Suzuki, found on twitter:
The right half of each image is exactly the same. But in the context of the two different left halves, it is interpreted as being either white and gold, or blue and black.)
But there is still more going on here. Another striking thing about the illusion is that it is quite unlike, e.g., Muller-Lyer and the checked shadow illusion, in that not all people experience it, and those that do, often do so differently. It is as if there is a perceptual equivalent of those who can roll their tongues and those who can’t. But it is too early to say whether the difference is genetic, as with tongue rolling ability; or something affected by learning and personality, such as being a night-owl (as Bevil Conway from Wellesley College has suggested), or one’s particular sensitivity to context in perception as I and fellow Sackler college Acer Chang speculate.
I think the most promising account of visual experience we have at present is the idea that what we see has as much to do with what inputs our brain expects to receive in a given situation as it does with what inputs our brain actually receives. But how one brain negotiates expected vs actual inputs to construct a colour experience might differ from how another brain does it. Thus, some people might perceive colours more on the basis of what is in front of them, while others might (unconsciously) take into account such things as: what kind of light source is likely to have been used in this photograph? And then even for those who do take more context into account, how they do so might vary from person to person, depending on their experience, interests, expertise, etc. For example, the night-owl/day-person issue mentioned before. Or the brain of a photographer or designer used to dealing with images in photoshop, adjusting white balance, etc. may very well use context to “create” colour experience in a way that is different from someone without that expertise/experience. (They might have a better understanding of how colours “behave” under a wide variety of lighting conditions, and so are not tricked into seeing the dress as gold and white.) There may even be low-level physiological/anatomical differences that determine exactly how and whether one will be sensitive to contextual effects when experiencing colour. But so far as I know, no one has yet identified the differences of context-sensitivity that are in play with this particular (and now notorious) dress.
Director, Centre for Cognitive Science
Faculty, Sackler Centre for Consciousness Science
University of Sussex
Comments/corrections to the above largely off-the-cuff and unresearched opinions very welcome!