Detecting foreign rhythm in native-language speech at birth

Humans begin tuning in to the prosody of their native language even before birth. Previous studies with newborns have shown language-specific processing of forward versus backward speech and of intonational contours, as well as sensitivity to iambic versus trochaic patterns in non-linguistic tone stimuli. The present study investigated newborns’ processing of temporal rhythm patterns in naturalistic native-language speech. Czech-learning newborns (N = 44) listened to naturally recorded, well-formed Czech utterances with either native Czech rhythm (virtually lacking acoustic cues to word-level stress) or foreign rhythm (featuring prolonged foot-initial syllables), while their hemodynamic activity was recorded. Results revealed larger hemodynamic responses to native-language speech with foreign-rhythm speech than to native-language speech with native rhythm. This difference was most pronounced in the right hemisphere, indicating right-lateralized processing of speech rhythm. Traditional theories of language development have suggested that only broad, between-class rhythm differences among languages are processed at birth. By showing that newborns discriminate between native and foreign rhythmic patterns even when their native language falls outside traditional rhythm classifications, the present findings evidence that gradient temporal cues alone are sufficient for early language discrimination.