Do you speak E-NG-L-I-SH? A comparison of foreigner- and infant-directed speech

Infant-directed speech has three main roles – it attracts attention, conveys emotional affect, and conveys language-specific phonological information, and each of these roles are reflected in certain components of the speech signal – pitch, rated affect, and vowel hyperarticulation. We sought to investigate the independence of these components by comparing British English speech directed to first language English learners (infants), and second language English learners (adult foreigners), populations with similar linguistic but dissimilar affective needs. It was found that, compared with British adult-directed speech, vowels were equivalently hyperarticulated in infant- and foreigner-directed speech. On the other hand, pitch was higher in speech to infants than to foreigners or adult British controls; and positive affect was highest in infant-directed and lowest in foreigner-directed speech. These results suggest that linguistic modifications found in both infant- and foreigner-directed speech are didactically oriented, and that linguistic modifications are independent of vocal pitch and affective valence.