Newborn babies can recognize the sound of their mother's voice at birth. But scientists are unsure which aspects of language are built into our brain through genetics and which are learned by listening in the womb. To investigate this question, a group of researchers in France studied 12 preterm infants, who were born two to three months' premature. At this stage brain connections are just beginning to form, meaning the infants' brain activity reflects the brain's initial organization rather than connections strengthened by learning, according to the researchers.

In the study, the scientists placed functional optical-imaging bands on the babies' heads to noninvasively monitor brain activity by passing infrared light through the infants' thin skulls. The light is absorbed or scattered depending on oxygen levels in the blood, which is a proxy for brain activity. The infants listened to male or female voices speaking simple sounds, such as “ga” or “ba.” The optical imaging revealed that the premature baby's brain could distinguish not only a speaker's gender but also the similar syllables. “What's really interesting is that the baby's brain can use the same sound networks we use later as an adult,” says neuroscientist Fabrice Wallois of INSERM at the University of Picardy Jules Verne in France.

This finding suggests that the neural connections used in adult language processing are present from very early in development, supporting the hypothesis that we are hardwired to understand some aspects of speech.