People who are tone deaf -- unable to hear differences in pitch and tone -- aren't just awful singers. At the most extreme, they're unable to perceive music, period. As Oliver Sacks, purveyor of all things strange in the brain, put it in his 2007 book Musicophilia, "Without these basic building blocks [of pitch and tone], there can be no sense of a tonal center or key, no sense of scale or melody or harmony -- and more than, in a spoken language, one can have words without syllables." And as a new study out last week showed, they have actual differences in brain structure from people for whom musical comes naturally.
The tone deaf have, as one of the first empirical studies of the condition defined it, a learning disability. Isabelle Peretz, a cognitive neuropsychologist, and her team at the University of Montreal reasoned that most children learn to sing just as they learn to speak -- seemingly automatically, and without formal instruction. Tone deaf children do not. Peretz gave the disorder the official name "congenital amusia." "Congenital" because it's innate: the brains of people with the disorder never developed the ability to process pitch. Amusia refers to that absence of musical perception. It's also, as Peretz later determined by studying amusica families, to some degree hereditary.
In the little more than a decade since tone deafness was first understood to be a disorder -- "not a myth but a genuine learning disability for music" -- researchers have been trying to figure out how it happens, and if there's anything to be done about it. The approximately four percent of the population with amusia, Peretz established, have usually grown up with normal exposure to music, and can be otherwise intelligent and well-educated. One early case she describes was a man reported by his piano teacher for his inability to sing, to tell the difference between two pitches, and to keep time. At the same time, Peretz notes, "this same subject could speak three foreign languages fluently."
In that first study, her team identified 11 adults who seemed likely to have truly amusia and subjected them to six tests that judged their perception of the melodic and temporal aspects of music, along with their musical memory (their ability to recognize songs). Her subjects all performed at least three standard deviations below the mean on at least two of the tests. That inability to recognize pitch, moreover, only applied to music -- not language. When the melody and lyrics of popular songs were presented separately, the amusic participants were generally able to recognize spoken lyrics, but were significantly impaired in their ability to tell whether they had heard a tune before.
It's been difficult for researchers to get over the idea that, with enough exposure to music, people born with amusia might somehow learn to listen. But even as music has become even more pervasive (think iPods), the condition persists. Last year, Peretz and her team looked into the potential to train young people with amusia, who they reasoned might have enough brain plasticity to be somewhat remediated. They gave 14 amusic 10- to 13-year-olds their basic test for music-hearing ability, then sent them home with MP3 players loaded with popular music (200 songs they found on the Internet, such as "No One" by Alicia Keys), which they were instructed to listen to for 30 minutes a day. Four weeks later, they were retested.
The kids tried. They ended up listening to their MP3 players for closer to 45 minutes a day. But at the end of the month, not only did they fail to improve on the tests, how poorly they scored correlated with how much music they reported listening to.
A new study published in the journal Brain takes it back a step by trying to figure out exactly where the brains of people with amusia go wrong. While subjecting participants to a basic melody-recognition test, researchers in Lyon, France studied their brain activity using magnetoencephalography (MEG) scanners. They found that amusic people's difficulties on the test stemmed from delayed or otherwise impaired functioning of two areas of the brain, the frontal and auditory cortexes, during the early encoding of melodic information. What's more, the researchers detected physical abnormalities in those brain areas. For example, they had more grey matter and less white matter than is usual in the frontal cortex. This "convergence of functional and structural brain differences" appears to explain people with congential amusia's inability to both process pitch and retain short-term memory of melodies.
"For the moment we cannot speak about remediation, cure, or treatment of amusia," one of the study's authors, Philippe Albouy, wrote to me in an email. But a next step could be to explore training programs that might improve people's pitch perception and memory -- those two basic skills essential to the ability to recognize music. They would probably have to be more focused than just making patients listen to more music. And while, sure, there are more life-and-death things we could be focusing on curing, understanding the neurological basis of amusia could help researchers understand other learning disorders, including the flip side of the coin: language impairments.
Even as the picture of what's going on in the brain becomes more clear, it's hard to really understand what it must be like to be completely tone deaf, just as, for people with amusia, it's probably hard to understand what the big deal is. A lot of people with amusia don't seem very distressed by their condition, but that could just be because they don't know what they're missing. The original participants in Peretz's study only identified themselves as unable to sing in tune because they had been informed of this inability by others. Still, the majority claimed not to appreciate music, with two going so far as to report finding music unpleasant and going out of their way to avoid it. And eight out of the eleven had difficulty dancing.