Colourblind Synaesthesia. A team of researchers (Milán, Hochel, González, Tornay, McKenney, Díaz Caviedes, Mata Martín, Rodríguez Artacho, Domínguez García and Vila) have a paper in the JCS setting out their experiments with an unusually interesting subject. This person, referred to as ‘R’, is colour blind for certain colours: but he also experiences a spectrum of synaesthetic colours in which he can make the full range of clear distinctions. The team believes its research shows that qualia can be accesible and useful to science.

Synaesthesia, the occurence of sensations (often sensations of colour) in association with unrelated stimuli, is an interesting but treacherous subject. Many people feel that the days of the week, or the numbers from one to ten, seem to have their own appropriate colours, and sceptics may feel that the whole phenomenon of synaesthesia is largely a case of people allowing their poetic feelings to run away with them. But there is a good deal of evidence to show that vivid synaesthesia is a real phenomenon. One of the earliest and most striking of reported cases is the classic one recounted by Luria in The Mind of a Mnemonist. His subject (referred to as ‘S’) formed exceptionally strong associations, which had the beneift of giving him a ‘photographic’ memory, but was also a considerable handicap as unwanted associations intruded into his life, making it impossible, for example, to buy an ice cream when something in the vendor’s voice called up a vivid impression of red hot coals.

R’s synaesthesia is not on this troublesome scale: he experiences colour sensations in connection with pictures and people, but he experiences the colour as internal, rather than seeing it ‘out there’ as some synaesthetes do. For him, there is a kind of code, with each synaesthetic colour having certain emotional connotations: in the case of people, for example, red means attractive, green means ill or dirty, purple means upbeat, yellow means envious or aggressive, and brown means old or uninteresting (the reader may be able to guess at R’s own approximate age). A portion of the team’s research was devoted to exploring these emotional connotations, and they claim, unconvincingly I think, that their results show the possibility of an inverted spectrum of emotions (I think they merely show that R’s emotional reactions are in some respects atypical: the sky for him evokes red, which makes it exciting, whereas it is more commonly seen as restful: but that doesn’t amount to an inverted emotional spectrum).

The exploration of synaesthesia in colour blind subjects is not new – Ramachandran and Hubbard have produced many interesting findings, including a subject who referred to colours he could experience synaesthetically, but never with his eyes, as ‘Martian’ colours. This naturally raises the question of whether the Martian colours were ones which people with normal vision are used to, or something genuinely stranger. How would we know?

The exploration of qualia recounted in the JCS piece rests on an ingenious use of the Stroop effect. This effect occurs where, for example, the subject is shown a series of colour words, and asked to say, not what colour they name, but what the colour of the font is. If you’ve tried this, you’ll know that it is more difficult to do quickly and accurately than you might suppose: much harder, in any case, than when font and word indicate the same colour. Now if you were completely colour blind, you would of course be immune to Stroop interference. The team devised experiments which showed that R did indeed fail to show Stroop effects in certain cases where other subjects suffered them, very plausibly because of his limited colour vision. However, when he was shown pictures which evoked dissonant synaesthetic colours, Stroop interference did occur.

This seems to show that R’s inner colour experience – his qualia? – cover the normal range, distinct from the range of colours he can actually distinguish with his eyes. Moreover, in a separate series of experiments, the team got him to match his synaesthetic colours with real ones, confirming that in his case at least they were not Martian in character. Does all this show that qualia are ‘a useful scientific concept’?

Interestingly, the paper quotes (and slightly misdescribes) one of the ‘intuition pumps’ used by Daniel Dennett. Two coffee tasters (Chase and Sanborn) have ceased to enjoy Maxwell House, but seemingly for different reasons. To one, it tastes the same as ever, but he no longer likes that taste: the other still likes that taste, but the coffee, although it has not changed chemically or in any other objective respect, no longer tastes that way to him. Dennett’s case is that this distinction, between the qualia and the taster’s reaction, is not ultimately sustainable. One of the taster’s wives ultimately straightens him out on the point: so he’s still having the same taste experience, but now doesn’t like it? But doesn’t the fact that he doesn’t like it mean, in itself, that the experience is different? There’s just no point in talking about qualia as distinct from our reactive dispositions.

What would Dennett say about R? I think he would say the research is an interesting exploration of those reactive dispositions, but that nothing here requires us to talk of qualia at all. R’s brain reacts to certain stimuli in ways which other people’s brains react to certain inputs from their eyes, though R himself lacks those inputs. But just because synaesthetic colour doesn’t come from the eyes, we mustn’t conclude that it has the inner, subjective quality of qualia. Indeed, by ingeniously naturalising synaesthetic colour, and showing it to be accessible to science, the team has arguably shown that it can’t be identified with qualia.

The team concludes that their research shows the coffee taster thought experiment actually makes no sense: the quale and the reaction ‘seem to be rigidly connected and cannot change independently’. Dennett might not be unhappy with that conclusion: why not take one more step, he might say, and draw the conclusion that talk of qualia is really only talk of reactions…?


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