What colour do you see?

From Aeon:

On 26 February 2015, Cates Holderness, a BuzzFeed community manager, posted a picture of a dress, captioned: ‘There’s a lot of debate on Tumblr about this right now, and we need to settle it.’ The post was accompanied by a poll that racked up millions of votes in a matter of days. About two-thirds of people saw the dress as white and gold. The rest, as blue and black. The comments section was filled with bewildered calls to ‘go check your eyes’ and all-caps accusations of trolling.

Vision scientists were quick to point out that the difference in appearance had to do with the ambiguity of ambient light in the photograph. If the visual system resolved the photograph as being taken indoors with its warmer light, the dress would appear blue and black; if outdoors, white and gold. That spring, the annual Vision Sciences Society conference had a live demo of the actual dress (blue and black, for the record) lit in different ways to demonstrate the way the difference of ambient light shifted its appearance. But none of this explains why the visual systems of different people would automatically infer different ambient light (one predictive factor seems to be a person’s typical wake-up time: night owls have more exposure to warmer, indoor light).

Whatever the full explanation turns out to be, it is remarkable that this type of genuine difference in visual appearance could elude us so completely. Until #TheDress went viral, no one, not even vision scientists, had any idea that these specific discrepancies in colour appearance existed. This is all the more remarkable considering how easy it is to establish this difference. In the case of #TheDress, it’s as easy as asking ‘What colours do you see?’ If we could be oblivious to such an easy-to-measure difference in subjective experience, how many other such differences might there be that can be discovered if only we know where to look and which questions to ask?

. . . .

Take the case of Blake Ross, the co-creator of the Firefox web browser. For the first three decades of his life, Ross assumed his subjective experience was typical. After all, why wouldn’t he? Then he read a popular science story about people who do not have visual imagery. While most people can, without much effort, form vivid images in their ‘mind’s eye’, others cannot – a condition that has been documented since the 1800s but only recently named: aphantasia. Ross learned from the article that he himself had aphantasia. His reaction was memorable: ‘Imagine your phone buzzes with breaking news: WASHINGTON SCIENTISTS DISCOVER TAIL-LESS MAN. Well, then, what are you?’

Ross went on to ask his friends about what it’s like for them when they imagine various things, quickly realising that, just as he took his lack of imagery as a fact of the human condition, they similarly took their presence of visual imagery as a given. ‘I have never visualised anything in my entire life,’ Ross wrote in Vox in 2016. ‘I can’t “see” my father’s face or a bouncing blue ball, my childhood bedroom or the run I went on 10 minutes ago… I’m 30 years old, and I never knew a human could do any of this. And it is blowing my goddamn mind.’

There is a kind of visceral astonishment that accompanies these types of hidden differences. We seem wedded to the idea that we experience things a certain way because they are that way. Encountering someone who experiences the world differently (even when that difference seems trivial, like the colour of a dress) means acknowledging the possibility that our own perception could be ‘wrong’. And if we can’t be sure about the colour of something, what else might we be wrong about? Similarly, for an aphantasic to acknowledge that visual imagery exists is to realise that there is a large mismatch between their subjective experiences and those of most other people.

Studying hidden differences like these can enrich our scientific understanding of the mind. It would not occur to a vision scientist to ask whether being a night owl might have an impact on colour perception, but a bunch of people on the internet comparing notes on how they saw a dress inspired just such a study. The study of aphantasia is helping us understand ways in which people lacking imagery can accomplish the same goals (like remembering the visual details of their living room) without using explicit imagery. How many other such examples might there be once we start looking? There is also, arguably, a moral imperative for us to study and understand these kinds of differences because they help us understand the various ways of being human and to empathise with these differences. It’s a sobering thought that a person might respond differently to a situation not just because they have a different opinion about what to do or are in possession of different knowledge, but because their experience of the situation is fundamentally different.

For most of my research career, I didn’t really care about individual differences. Like most other cognitive scientists, my concern was with manipulating some factor and looking to see how this manipulation affected the group average. In my case, I was interested in the ways that typical human cognition and perception is augmented by language. And so, in a typical experiment, I would manipulate some aspect of language. For example, I examined whether learning names for novel objects changed how people categorised, remembered and perceived them. These were typical group-effect studies in which we compare how people respond to some manipulation. Of course, with any such study, different people respond in different ways, but the focus is on the average response.

For example, hearing ‘green’ helps (most) people see the subtle differences between more-green and less-green colour patches. Interfering with language by having people do a concurrent verbal task makes it harder for (most) people to group together objects that share a specific feature, such as being of a similar size or colour. But most people aren’t everyone. Could it be that some people’s colour discrimination and object categorisation is actively aided by language, but other people’s less so? This thought led us to wonder if this could be another hidden difference, much like aphantasia. In particular, we began to look at inner speech, long thought to be a universal feature of human experience.

Most people report having an inner voice. For example, 83 per cent (3,445 out of 4,145 people in our sample) ‘agree’ or ‘strongly agree’ with the statement ‘When I read I tend to hear a voice in my mind’s ear.’ A similar proportion – 80 per cent – ‘agree’ or ‘strongly agree’ with the statement ‘I think about problems in my mind in the form of a conversation with myself.’ This proportion goes up even more when asked about social problems: 85 per cent ‘agree’ or ‘strongly agree’ with the statement ‘When thinking about a social problem, I often talk it through in my head.’

But 85 per cent is hardly everyone. What about those who disagree with these statements? Some of them report experiencing an inner voice only in specific situations. For example, when it comes to reading, some say that they hear a voice only if they deliberately slow down or are reading something difficult. But a small percentage (2-5 per cent) report never experiencing an inner voice at all. Like those with aphantasia who assume their whole lives that visual imagery is just a metaphor, those with anendophasia – a term Johanne Nedergaard and I coined to refer to the absence of inner speech – assume that those inner monologues so common in TV shows are just a cinematic device rather than something that people actually experience. People with anendophasia report that they never replay past conversations and that, although they have an idea of what they want to say, they don’t know what words will come out of their mouths until they start talking.

It is tempting to think that there is a trade-off between thinking using language and thinking using imagery. Take the widespread idea that people have different ‘learning styles’, some being visual learners and others verbal learners (it turns out this idea is largely incorrect). When it comes to imagery and inner speech, what we find is a moderate positive correlation between vividness of visual imagery and inner speech. On average, those who report having more visual imagery also report experiencing more inner speech. Most who claim to not experience inner speech also report having little imagery.

This raises the question of what their thoughts feel like to them. When we have asked, we tend to get answers that are quite vague, for example: ‘I think in ideas’ and ‘I think in concepts.’ We have lots of language at our disposal that we can use to talk about perceptual properties (especially visual ones) and, of course, we can use language to talk about language. So it is not really surprising that people have trouble conveying what thoughts without a perceptual or linguistic format feel like. But the difficulties in expressing these types of thoughts using language don’t make them any less real. They merely show that we have to work harder to better understand what they are like.

Differences in visual imagery and inner speech are just the tip of the iceberg. Other hidden differences include synaesthesia, Greek for ‘union of the senses’, in which people hear lights or taste sounds, and Eigengrau, a German word for the ‘intrinsic grey’ we see when we close our eyes. Except not all of us experience Eigengrau. About 10 per cent in our samples claim their experience is nothing like Eigengrau. Instead, when they close their eyes, they report seeing colourful patterns or a kind of visual static noise, like an analogue TV not tuned to a channel.

Our memory, too, seems to be the subject of larger differences than anyone expected. In 2015, the psychologist Daniela Palombo and colleagues published a paper describing ‘severely deficient autobiographical memory’ (SDAM). A person with SDAM might know that they went on a trip to Italy five years ago, but they cannot retrieve a first-person account of the experience: they cannot engage in the ‘mental time travel’ that most of us take for granted. As in other cases of hidden differences, these individuals tend not to realise they are unusual. As Claudia Hammond wrote for the BBC about Susie McKinnon, one of the first described cases of SDAM, she always ‘assumed that when people told in-depth stories about their past, they were just making up the details to entertain people.’

Link to the rest at Aeon and thanks to A. for the tip.