The Chinese need both sides of the brain to grapple with challenges of Mandarin, but English speakers listen with only half their minds on the job.
Sophie Scott, a psychologist at the Wellcome Trust, and colleagues from hospitals in Oxford and London performed brain scans on volunteers as they listened to their native languages.
When English speakers heard the sound of Mockney, Mersey or Geordie, their left temporal lobes lit up on screen. When Mandarin Chinese speakers heard their native tongue, there was a buzz of action in both the right and left temporal lobes.
"We were very surprised to discover that people who speak different sorts of languages use their brains to decode speech in different ways, said Dr Scott. "It overturned some long-held theories."
The left temporal lobe is normally associated with piecing sounds together into words; the right with processing melody and intonation.
In Mandarin, a different intonation delivers a different meaning: the syllable "ma", for instance, can mean mother, scold, horse or hemp according to its musical sound.
"Speech really is a complex sound," said Dr Scott. "As well as understanding words, the brain uses the way in which words are spoken, such as intonation and melody, to turn spoken language into meaning. This system has to be robust and flexible enough to deal with variations in speech sounds such as regional accents. We think Mandarin speakers interpret intonation and melody in the right temporal lobe to give correct meaning to the spoken words."
The research throws new light on how speech is understood, and could one day lead to new treatments for people whose understanding of language has been impaired by stroke.
Dr Scott and her colleagues will put their research on show at the Royal Society summer science exhibition in London tomorrow, Wednesday and Thursday. The study suggests that language itself might affect the way the brain develops in a young child.
It could explain why native speakers of English find it so extraordinarily hard to learn Mandarin. It might also help doctors understand what happens when people have to learn speech comprehension all over again, for instance after a stroke, or after being fitted with a cochlear implant hearing aid.