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Tone deaf shed light on origin of language

Music and speech A study involving 'tone deaf' people supports Darwin's idea that music and language evolved from the same emotional "musical protolanguage".

The research is reported today in the journal Proceedings of the National Academy of Sciences.

First author Professor Bill Thompson of Macquarie University in Sydney says if Charles Darwin was correct, then both music and language should share brain circuitry.

"If that's true then the vestiges of that protolanguage should still be in some shared neural resources of these two forms of communication," says Thompson, who is head of psychology and also a chief investigator in the Australian Research Council Centre of Excellence in Cognition and its Disorders.

Thompson says the strongest link between music and language is that they both involve emotional communication through changes in pitch.

The importance of pitch in music is obvious. In speech too, communication of emotion depends on changing pitch, known as 'speech prosody'.

"We all know people who have difficulty perceiving tone of voice. They just don't get it when we're being ironic. They don't get it when we're irritated. It just goes over their head," says Thompson.

He thinks Darwin was right about the shared roots of language and music and such people have what is essentially a music-related problem.

Study of 'tone deaf' people

To investigate this link between music and language, Thompson and colleagues studied people diagnosed with "congenital amusia", who have difficulty perceiving changes in pitch and therefore find it hard to hold a tune.

The researchers were interested in whether this impairment also made it hard for people to pick up emotional communication in speech.

Thompson and colleagues matched 12 people with congential amusia with 12 controls and tested them with a battery of tests designed to investigate their sensitivity to emotional prosody.

The test participants had to listen to 96 spoken phrases and identify whether the tone of voice communicated happiness, tenderness, fear, irritation, sadness or no emotion.

The researchers found the people with congenital amusia were up to 20 per cent less likely, in some cases, at identifying the emotion, compared to the controls.

"When pitch was important they had difficulty, and confused the emotions," says Thompson.

"We conclude that people with congenital amusia have difficulty perceiving emotion from tone of voice."

Shared circuitry

Thompson says the findings suggest that the ability to perceive the emotion coded in tone of voice may share some of the same brain circuitry as our musical ability.

He suspects areas of the brain that connect auditory pitch processing and emotions are damaged in people with amusia.

This discovery supports Darwin's ideas that music and language both evolved from a common protolanguage that involved these parts of the brain.

The latest findings build on previous research by Thompson and colleagues that found a year of music training boosted the sensitivity of children to speech prosody, compared to children trained in other subjects, like drama.

Compensation

But does all this mean that people who are good with their pitch are more emotionally intelligent?

Not so, says Thompson. Emotional intelligence is made up of a lot more than reading people's tone of voice, he says.

And people with congenital amusia are likely to develop strategies to compensate for their disability.

"These people seem to be able to attend to other non-auditory cues and may even have enhanced sensitivity in other areas such as the ability to read body language" says Thompson.