Dr Sophie Scott and colleagues at the Wellcome Trust carried out brain scans on a group of Mandarin and English speakers.
They found that the left temporal lobe, which is located by the left temple, becomes active when English speakers hear English, but both the left and right temporal lobes become active when they hear Mandarin.
Unlike English, Mandarin speakers use intonation to distinguish between completely different meanings of particular words. The researchers believe that this need to interpret intonation is why Mandarin speakers need to use both sides of their brain. The right temporal lobe is normally associated with being able to process music or tones. [Via BBC News: http://news.bbc.co.uk/2/hi/health/3025796.stm]