A test of 80 babies showed a baby’s ability to recognize language used by their mothers.
Discovery.com has more details:
To see just how early those abilities develop, Kuhl and colleagues tested 40 American newborns and 40 Swedish newborns, all between seven hours and three days old. While still in the hospital, each infant listened through headphones to 17 computer-generated examples of the English vowel sound used in syllables like “fee” and 17 examples of the Swedish vowel sound used in syllables like “fy.” During the experiment, babies sucked on sensor-equipped pacifiers.
When exposed to vowel sounds from their non-native language, babies sucked longer than they did if they heard vowel sounds that their mothers frequently spoke, the researchers will report in the journal Acta Paediatrica. Sucking longer is an established response in infants to something that is unfamiliar or novel to them.
“The results of our study support the hypothesis that language experienced in utero affects vowel perception,” the researchers wrote. “These results suggest that birth is not a benchmark that reflects a complete separation between the effects of nature versus those of nurture on infants’ perception of the phonetic units of speech.”