The cap's out of the bag: Place assimilation is common in infant-directed speech

Adult-directed speech (ADS) contains many words that deviate from their canonical form due to connected speech processes such as coronal place assimilation (e.g. ‘cat’ realized as ‘cap’ in the phrase ‘cat box’). Here, we ask how often this occurs in Infant-directed speech (IDS), which is often believed to be articulated more clearly than ADS. Mothers of 18-month-olds were recorded producing pairs of phrases that did or did not license assimilation (e.g., cat box/cap box) while addressing either their infant (IDS) or another adult (ADS). Both scripted and unscripted utterances were collected. Key phrases were extracted and presented to adults for identification in a forced choice task, with the expectation that listeners would more accurately identify tokens with less assimilation. Surprisingly, adults identified phrases more accurately in ADS than IDS, suggesting that assimilation occurs frequently in IDS, as it does in ADS, regardless of whether the speech is scripted or not.