IF YOUR singing sends people scurrying to find earplugs, blame your ancestors. According to a study of musically gifted and tone-deaf twins, your ability to judge pitch is largely determined by your genes.
Tim Spector of St Thomas' Hospital in London and his colleagues hoped to find out whether early musical experiences or genes determine people's ability to judge whether a melody is being played in tune. "I guessed there would be a small genetic component, but that environment--say having a family environment where music was always played--would be a greater factor," says Spector.
To test this, his team recruited 136 pairs of identical twins and 148 pairs of non-identical twins. Identical twins have exactly the same genes, while fraternal twins share about half of their genes, like ordinary siblings.
The volunteers listened to 26 well-known tunes, including Silent Night and The Star-Spangled Banner. Nine were played correctly, but the rest included notes that were one or two semitones off-key. The twins had to judge whether each melody was in tune or not.
The gulf between the high and low scorers was enormous. Around a quarter of the listeners scored full marks. But 1 in 20 was deemed "tune deaf", spotting incorrect melodies with an accuracy no better than they would be expected to achieve by chance. "You can't believe that some people don't know Yankee Doodle Dandy's being played so badly," says Spector.
But the most surprising finding was that identical twins were much more likely than non-identical twins to have very similar scores, suggesting that your genetic make-up largely determines your ability to judge pitch. Spector's team concludes that this skill is roughly 80 per cent hereditary.
He adds that this strongly suggests that music lessons can't turn a tone-deaf child into a musical maestro. "Once you realise that there's a huge variety in what other people are hearing and that the cause is predominantly genetic, you can see why it's going to be virtually impossible to change them," says Spector.
"I think the twin study is very good, and strongly suggests a genetic component to pitch cognition," says Peter Gregerson, a geneticist at North Shore University Hospital in Manhasset, New York. He suspects that many genes act together to influence our judgement of pitch: "Complex cognitive abilities like this are likely to have a very complex genetic basis."
More at: Science (vol 291, p 1969) To find out if you are "tune deaf", take the distorted tunes test at www.newscientist.com/dn.jsp?i=497
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