People might be wondering what it is that I’m doing in San Diego, beyond my rather nebulous description of ‘research’. Right now I’m working in the research labs of V. S. Ramachandran at the University of California, San Diego Center for Human Information Processing on an experiment to investigate an interesting condition called synaesthesia. Synaesthesia is basically what happens when your senses get mixed up and interconnected in strange ways. For example, when some synaesthetes read letters or digits, they’ll see them coloured (even when they don’t originally have colours). Others will associate sounds, music, shapes or even people with colours or smells. Essentially, any combination of the senses is possible, although grapheme-colour synaesthesia (a grapheme is a character) is the most common.

Estimates of the prevalence of synaesthesia vary from 1 in 200 to 1 in 20,000. The people in the lab I’m working at tend towards the former number. If that’s the case, chances are that you know someone personally who has synaesthesia – the only problem is that synaesthetes are either embarrassed about talking about their experiences, or they simply think that everyone is like them. One day the graduate student I’m working with was talking to a friend about a synaesthete who, when listening to speech, would see the words scroll along the bottom field of his vision, like subtitles. The friend said, “But doesn’t everyone have that?”

It’s generally thought that synaesthesia has a significant genetic component, and because it tends to be passed along the female line, it probably resides in the X chromosome. For a long time it was believed this couldn’t be true because Vladimir Nabokov had synaesthesia and so did his son Dmitri – so this meant that it couldn’t be in the X chromosome (sons inherit only the Y chromosome from their fathers). Of course, it turned out that Nabokov’s wife was also a synaesthete.

Why is synaethesia a big deal all of a sudden? Synaesthesia was ignored for a long time by psychologists due to the long-lasting age of behaviourism (‘don’t listen to what the subject says, just measure him’), and in any case many people simply thought synaesthetes were speaking metaphorically, e.g. “This cheese has a pretty sharp taste.” A series of pioneering experiments conducted over the last ten and twenty years have completely reversed this, showing that not only is synaesthesia a genuine phenomenon, but it’s also a perceptual one. By this, I mean that synaesthetes really see (say) colours when they see numbers. It’s not that they have an eidetic memory and can learn the sensory associations, they really experience them.

This has resulted in some interesting findings. Synaesthetes appear to have superior memory, and their ability to associate senses makes for good artists and writers. One of the things we’ll be doing in the lab is to talk to a trilingual synaesthete who experiences colours when she hears words – will the same word in the different languages elicit the same colour? Or will the phonological properties of the word – the sound of the word – matter more than the semantic meaning?

The point behind all of this is not merely to have a look at an interesting new condition. Synaesthesia also promises to shed light on some of the more profound questions about attention, perception, information processing in the brain, and consciousness. As such, it’s a very ‘sexy’ new topic and researchers are flocking towards it. It’s already been featured in a computer game, Rez (which is also very fun) and the other day I saw a mention of it in a Stephen Baxter SF novel. The main thing I’m working on here is a metacontrast experiment that’s aiming to find out exactly when the experience of colour occurs in the processing of visual information in synaesthetes. It’s a useful experience for me, especially given that many key findings about synaesthesia were made by people in the lab I’m in now.