Perceived emotions in infant-directed narrative across time and speech acts

One important function of infant-directed speech (IDS) is to express positive emotions towards the baby. This has been shown based on prosodic parameters before, but parameters such as f0 and energy encode emotion expression only indirectly. In this study, we aim to access emotion expression (arousal and valence) in IDS directly, through labellers’ perception. Recordings were made in the first 18 months of the baby: in the age of 0, 4, 8 and 18 months. The sentences and the contexts were fixed. Our questions were the following: (1) Does emotion expression in IDS and adult-directed speech (ADS) differ in narratives when sentences and contexts do not vary? (2) Do the strength and polarity of emotions change over time in mothers’ speech up to 18 months of the baby? (3) Do observed differences pattern similarly in various types of speech acts? Both arousal and valence scores were higher in IDS. No changes in IDS were observed during the first 18 months. Requests received higher arousal and valence scores than exclamations, but in IDS, they only differed by valence. This means that these speech acts are only held apart consistently by valence in the two registers, not by arousal.