Newborns’ neural tuning to the native language is revealed by infant-directed speech

Newborn infants process a native language differently than a distinct non-native language, showing behavioral preference for the former and language-specific neural activation. At the same time, young infants show preferences for infant-directed speech (IDS) over adult-directed speech (ADS) and evidence suggests this preference is mirrored at the neural level. There is a confound: most studies assessing young infants’ responses to native versus non-native languages employ IDS stimuli, leaving it unclear whether IDS enhances or diminishes language-specific processing. Here, we examined whether newborns (n=62, 1–6 days old) differentially track their native versus an unfamiliar language and whether this differs between IDS and ADS.Newborns showed stronger neural tracking of native-language Czech than non-native language Russian speech in IDS, whereas this language-specific difference was reduced or absent in ADS. In particular, newborns tracked their native-language infant-directed speech most strongly in the delta band, reflecting an early sensitivity to slow temporal structure in native-language speech. These findings indicate that early neural processing is tuned to the rhythmic properties of the native language, especially when the language is presented in infant-directed speech. Sensitivity to slow temporal structure may scaffold early segmentation, attentional organization, and the emergence of more fine-grained linguistic representations. Together, the results show that newborns can discriminate native from non-native speech and that IDS enhances the neural encoding of native-language rhythms, providing a foundation for early language acquisition.