Tone, pitch, and cadence—what linguists call intonation contours—enhance or subvert meaning, and transmit rich information about the speaker’s emotions. Infants sort what they hear through the superior temporal sulcus (STS), located just above the ear. At four months all auditory information—whether their mother’s voice or a car horn—is attended to by the STS. But by seven months, babies start singling out human voices as the only sounds that trigger attention from the STS,6 and the STS shows especially heightened activity when that voice carries emotion. This little piece of our brain is
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