What’s really interesting about the dress colour illusion

dress-color-illusionA 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.

Ron Chrisley
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!


4 thoughts on “What’s really interesting about the dress colour illusion

  1. Nice article – even nicer long explanation.

    But a problem with the images that Keisuke found is that the right halves are *not* the same colour (the point being made still stands, of course).

    Screen grabs attached (if the email system allows me to), just swap between them!


    On 28 February 2015 at 09:59, PAICS: Philosophy of AI and Cognitive Science

    • One more thing: As far as “seeing is understanding” goes, I think we might have some common ground here. I reject the idea of the given as uninterpreted sense data. If there is a given, it is a given with content, for which not only the notion of correctness applies, but also the notion of aspectual shape/mode of presentation. For there to be a given for someone, their perceptual-cognitive apparatus must make it the case that the world is presented as being some way or other. If one likes, one can see this “sense-making” (to abuse a term) as a kind of understanding, although it is different from the conscious, personal-level, endogenously controlled, rationally governed, systematicity supporting processes that some people more usually apply the term “understanding” to.

  2. Mike,

    The screen grabs didn’t come through. Please email them to me and I will try to post them.

    (What follows is a slightly edited version of a note I left on Mike’s Facebook page, where he suggested that the dress colour illusion demonstrates the truth of conceptualism: “Seeing *is* understanding; there is nothing raw and unprocessed which comes first.”)

    As far as demonstrating conceptualism goes, I don’t see how the fact different people have different colour experiences when viewing the same photo has any bearing on the issue. Why can’t the non-conceptualist just say that the way that the dress (non-conceptually) strikes one group of people is different from how it (non-conceptually) strikes another group? Why must the difference between the groups be a conceptual difference? In fact, in some ways the experience in this illusion, like many others, does not seem to respect the norms of rational revision that govern concepts, so like those illusions, it could instead be used as a demonstration of the falsity of conceptualism. Also, I am one of those (few?) people who is willing to entertain the idea that one’s conceptual repertoire might affect one’s non-conceptual experience, even if no concept is an actual constituent of that experience. So even if the difference is explained conceptually, it does not refute the notion of a non-conceptual “given”. Finally, even if one could show in a particular case that some experience is exhaustively conceptual, it would take more work to *demonstrate* that *all* experiences *must* be *wholly* conceptual.

    PS So it seems we have a meta-illusion: isn’t it funny how two people can look at the same illusion, and one sees a demonstration of conceptualism, while the other sees something completely different? 🙂

  3. A year on, I thought I would have a look to see what has been learned in the meantime about the dress illusion. A key question is: what explains the striking individual differences (or the two camps)? I found the following study by Laufer-Sousa, Hermann and Conway:


    A key passage is here:

    “Many hypotheses have been proposed regarding the source of the individual differences. Our study shows that age and gender are the two most significant predictors. But these correlations do not reveal the causes of the individual differences. A plausible hypothesis is that different people have different priors about the spectral content of the illuminant, with the population of priors varying along the daylight locus [S4]….

    Does the extent to which one is exposed to a given illuminant (blue-sky daylight versus warm incandescent light) predict the colors one sees the dress? We attempted to answer this question by asking subjects about their sleep-wake patterns. We found a slight, but insignificant trend: subjects reporting more awake time during the day were slightly more likely to see the dress as W/G. Although the results provided by directly surveying sleep-wake patterns are at present inconclusive (we may need to sort data by longitude etc.), our results provide some support for the chronotype hypothesis. Older subjects and women are more likely to have a daytime chronotope [6]. Consistent with this, we found that these two variables significantly predicted a higher likelihood of reporting the dress to be W/G. Lens density, corneal coloration, and other optical properties of the eye vary with age. It is also a possibility that these factors contribute to the individual differences observed presently.”


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