The colour of music

Published on 17/01/2005 00:05

I’VE JUST discovered I have a mild form of synaesthesia. Is it romantic or fatal? More the former, I would say. It is where the brain does not have a clear division between the reception of different sensations. For instance, the Finnish composer Sibelius saw notes as colours and smelled them too. Most commonly linked sensations are visual and auditory, taste and touch, olfactory and auditory. Most synaesthetes are women; assessments vary, but it may be eight times more common in females.

Even more oddly, there is a link with people who have odd experiences such as dj vu, premonitions or clairvoyance. In musical synaesthetes, it is not uncommon to find the wonderful gift of perfect pitch.

I’ve always been aware that the days of the week have distinct colours, as do the names of months, numbers and letters of the alphabet, though they’ve faded with the years. As a child I discovered my sister had the same peculiarity, though her colour system was different. Since then I had assumed it was normal. My type seems to be the commonest, but mingled experiences of smell, taste and touch are much rarer.

Some descriptions are quite exotic, for instance piano tones seen as blue fog, guitar notes perceived as floating orange stripes in front of the body; phone numbers remembered as a multi-coloured string of pearls, sensing music as the aroma of hay, smelling a rose as a touch upon the skin, relishing the taste of pepper sauce as sharp, pointy triangles. The number five might be middle-aged, female, gentle and the colour of honey.

Some people even see the world in different colours according to mood.

Naturally, the psychologists have tried to claim the phenomenon for their own, but affected people have proved stubbornly mentally normal, apart from, in general, having rather good memories and unusual artistic talent.

Children who try to explain their tangled sensations are usually faced with blank incomprehension, like one little girl who announced to her teacher, "four plus four is red," to the mocking hilarity of her peers.

Synaesthesia has been recognised for about 300 years, and until recently was thought to be very rare; estimates of 1 in 2,000 at the most. But research in the last decade puts it as high as 1 in 100, including the mildest examples of mixed messages. Within an individual, the links are very consistent, so it is different from association-testing and having hallucinations. However, related phenomena are seen in LSD takers and schizophrenics. I recall one schizophrenic reporting severe pain which she felt in the curtains around the bed.

Besides Sibelius, the composers Skrjabin, Rimsky-Korsakov and Messiaen had the trait, also artists Hockney and Kandinsky and the author Nabokov.

Synaesthesia holds a particular fascination for the artistic world. It is a desirable gift, an enhancement of sensuality, a manifestation of creativity, and has inspired volumes of poetry, music, literature, folklore and analysis. Periodically it has stimulated multi-modal concerts of music and light and sometimes perfume. Meanwhile the science world has been ambivalent about researching something so wholly subjective.

Current science accepts that synaesthesia is inherited, as an X-linked trait in many cases, which explains the female predominance. It is possible that all infants are born with muddled sensory experiences, for instance, in them a sound triggers auditory, visual and tactile vibes. This state of psychedelia is due to hyper-connectivity between sensory parts of the brain, and normally about the age of four months these connections are automatically pruned to leave more specific responses. Synaesthetes have a genetic mutation that interferes with this pruning. There are probably genetic variants to explain the different sensory melanges, and extensive connections left between brain areas that deal with abstract concepts seem likely to convey a marked degree of artistic creativity as well as disabling distraction in ordinary, everyday matters.

Magnetic resonance imaging has clarified with some precision the colour vision areas involved in the visual cortex of the brain. The limbic system which controls consciousness is connected, as well as other sensory centres. Some synaesthetic experiences occur outwith the body, which implicates the angular gyrus, thought to be the seat of "out of body" experiences. Synaesthesia research may cast new light on perception, thought, consciousness and language.

• If you think you may be a covert synaesthete and would like to contribute to pushing forward the frontiers of knowledge, there is a website where you can take a test: www.bbc.co.uk/science/humanbody/mind/index_surveys.shtml