Connecting stimulus-driven attention to the properties of infant-directed speech - Is exaggerated intonation also more surprising?

The exaggerated intonation and special rhythmic properties of infant-directed speech (IDS) have been hypothesized to attract infant’s attention to the speech stream. However, studies investigating IDS in the context of models of attention are few. A number of such models suggest that surprising or novel perceptual inputs attract attention, where novelty can be operationalized as the statistical predictability of the stimulus in a context. Since prosodic patterns such as F0 contours are accessible to young infants who are also adept statistical learners, the present paper investigates a hypothesis that pitch contours in IDS are less predictable than those in adultdirected speech (ADS), thereby efficiently tapping into the basic attentional mechanisms of the listeners. Results from analyses with naturalistic IDS and ADS speech show that IDS has lower overall predictability of intonation across neighboring syllables even when the F0 contours in both speaking styles are normalized to the same frequency range.