Language experienced in utero affects vowel perception after birth: a two-country study

Aims To test the hypothesis that exposure to ambient language in the womb alters phonetic perception shortly after birth. This two-country study aimed to see whether neonates demonstrated prenatal learning by how they responded to vowels in a category from their native language and another non-native language, regardless of how much postnatal experience the infants had. Method A counterbalanced experiment was conducted in Sweden (n=40) and the USA (n=40) using Swedish and English vowel sounds. The neonates (mean postnatal age=33h) controlled audio presentation of either native or non-native vowels by sucking on a pacifier, with the number of times they sucked their pacifier being used to demonstrate what vowel sounds attracted their attention. The vowels were either the English/i/or Swedish/y/in the form of a prototype plus 16 variants of the prototype. Results The infants in the native and non-native groups responded differently. As predicted, the infants responded to the unfamiliar non-native language with higher mean sucks. They also sucked more to the non-native prototype. Time since birth (range: 775h) did not affect the outcome. Conclusion The ambient language to which foetuses are exposed in the womb starts to affect their perception of their native language at a phonetic level. This can be measured shortly after birth by differences in responding to familiar vs. unfamiliar vowels.