DO PEOPLE cover their ears when you step up to the karaoke mike? Can鈥檛 tap
your foot in time to a melody? Can鈥檛 even recognise a simple tune like Happy
Birthday? If the answer is yes, you鈥檙e not just tone-deaf, you鈥檙e
鈥渢耻苍别-诲别补蹿鈥�.
鈥淔or these patients, listening to music is like listening to a foreign
language,鈥� says Isabelle Peretz of Montreal University in Canada, who identified
congenital amusia four years ago. Tune-deaf people are perfectly normal in other
ways, she explains. They are intelligent, have no history of mental illness and
were exposed to music as children. They just cannot comprehend the basic
components of melody such as meter, rhythm and pitch and consequently do not
feel any emotion when listening. The disorder seems to affect men and women
equally.
Peretz鈥檚 research鈥攊ncluding one study on 11 people鈥攈as shown that
tune-deaf people cannot distinguish intervals of about two semitones or less. A
semitone is the smallest interval in Western scales and most people can detect
an interval of half that. Tune-deaf people also have difficulty recognising
鈥渨rong鈥� notes in popular tunes and spotting musical dissonance.
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In research presented at a recent meeting of the Association for Research in
Otolaryngology in Florida, a team led by Tim Griffiths at the University of
Newcastle upon Tyne described one person who can鈥檛 detect sound patterns in
music. The woman was asked if she could tell the difference between two notes.
In one test the notes differed in the amount of vibrato (pitch variation) while
in another they differed in the amount of tremolo (volume variation). In both
cases, the differences had to be huge for her to notice. Tests showed that there
was nothing wrong with her hearing.
Interestingly, other work by Peretz suggests that tune-deafness does not seem
to impair language ability. People don鈥檛 have difficulty recognising voices or
spotting intonation in language such as the upward inflection at the end of a
question. This may be because pitch jumps in speech tend to be quite large and
obvious. It also implies that there are specific modules in the brain dedicated
to processing music which are separate from speech modules.
But Mireille Besson of the Centre for Research in Cognitive Neurosciences in
Marseille has found contrary evidence implying that music and language
processing are linked. Her group showed that the brain responds similarly to an
unexpected jump in a melody and an unexpected sentence intonation, such as a
voice going down in pitch at the end of a question. 鈥淧eretz鈥檚 work is good
evidence for the modular view,鈥� she says, 鈥渂ut there are other ways to interpret
the data. The brain is very plastic.鈥�
Griffiths says no one is sure how common the disorder is, but he believes
that there are more sufferers than we realise because people don鈥檛 admit to it.
鈥淪ufferers might put CDs on when friends come round to dinner in an effort to
pretend they like music,鈥� he says.