By Philip Ball

Remember the Mozart effect? Thanks to a suggestion in 1993 that listening to Mozart makes you cleverer, there has been a flood of compilation CDs filled with classical tunes that will allegedly boost your baby's brain power.

Yet there's no evidence for this claim, and indeed the original "Mozart effect" paper did not make it. It reported a slight, short-term performance enhancement in some spatial tasks when preceded by listening to Mozart as opposed to sitting in silence. Some follow-up studies replicated the effect, others did not. None found it specific to Mozart; one study showed that pop music could have the same effect on schoolchildren. It seems this curious but marginal effect stems from the cognitive benefits of any enjoyable auditory stimulus, which need not even be musical.

The original claim doubtless had such inordinate impact because it plays to a long-standing suspicion that music makes you smarter. And as neuroscientists Nina Kraus and Bharath Chandrasekaran of Northwestern University in Evanston, Ill., point out in a review published July 20 in Nature Reviews Neuroscience, there is good evidence that music training reshapes the brain in ways that convey broader cognitive benefits. It can, they say, lead to "changes throughout the auditory system that prime musicians for listening challenges beyond music processing."

This is no surprise. Many sorts of mental training and learning alter the brain, just as physical training alters the body, and learning-related structural differences between the brains of musicians and non-musicians are well established. Moreover, both neurological and psychological tests show that music processing draws on cognitive resources that are not music-specific, such as pitch processing, memory and pattern recognition--so cultivating these mental functions through music would naturally be expected to have a wider pay-off. The interactions are two-way: the pitch sensitivity imbued by tonal languages such as Mandarin Chinese, for example, enhances the ability to name a musical note just from hearing it (called absolute pitch).

We can hardly be surprised, meanwhile, that music lessons improve children's IQ, given that they will nourish general faculties such as memory, coordination and attentiveness. Kraus and Chandrasekaran now point out that, thanks to the brain's plasticity (the ability to "rewire" itself), musical training sharpens our sensitivity to pitch, timing and timbre, and as a result our capacity to discern emotional intonation in speech, to learn our native and foreign languages, and to identify statistical regularities in abstract sound stimuli.

Music to our ears

Yet all these benefits of music education have done rather little to alter a common perception that music is an optional extra to be offered only if children have the time and inclination. Ethnomusicologist John Blacking put it more damningly: we insist that musicality is a rare gift, so that music is to be created by a tiny minority for the passive consumption of the majority. Having spent years among African cultures that recognized no such distinctions, Blacking was appalled at the way this elitism labeled most people "unmusical."

Kraus and Chandrasekaran rightly argue that the marginalization of music training in schools "should be reassessed" in the light of the benefits it may offer by "improving learning skills and listening ability." But it will be a sad day when the only way to persuade educationalists to embrace music is via its side effects on cognition and intelligence. We should be especially wary of that argument in this age of cost-benefit analyses, targets and utilitarian impact assessments. Music should indeed be celebrated (and studied) as a gymnasium for the mind; but ultimately its value lies with the way it enriches, socializes and humanizes us qua music.

And while in no way detracting from the validity of the call for music to be essential in education, it's significant that musical training, like any other pleasure, has its hazards when taken to excess. I was recently privileged to discuss with the pianist Leon Fleisher his traumatic but fascinating struggle with focal dystonia, a condition that results in localized loss of muscle control. Fleisher's dazzling career as a concert pianist was almost ended in the early 1960s when he found that two fingers of his right hand insisted on curling up. After several decades of teaching and one-handed playing, Fleisher regained the use of both hands through a regime of deep massage and injections of botox to relax the muscles. But he says his condition is still present, and he must constantly battle against it.

Focal dystonia is not a muscular problem (like cramp) but a neural one: over-training disrupts the feedback between muscles and brain, expanding the representation of the hand in the sensory cortex until the neural correlates of the fingers blur. It is the dark side of neural plasticity, and not so uncommon--an estimated one in a hundred professional musicians suffer from it, although some do so in secrecy, fearful of admitting to the debilitating problem.

We would be hugely impoverished without virtuosi such as Fleisher. But his plight serves as a reminder that hot-housing has its dangers, not only for the performers but (as Blacking) suggests for the rest of us. Give us fine music, but rough music too.

Philip Ball's latest book is The Music Instinct (Bodley Head).