Emotional Speech Processing in Infants and Adults: A Behavioral and Electrophysiological Investigation

Abstract

Emotional prosody is integral to successful communication as it conveys the speaker’s emotional state and shapes the meaning of the words and sentences. Timely processing of vocal emotion facilitates speech comprehension as well as social interactions. However, very few studies have examined how infants process emotional speech prosody and how this ability develops from infancy to adulthood. The current dissertation includes three original studies to address emotional speech processing from a developmental perspective. The first study aimed to characterize 3-12-month-old infants’ listening attention to basic emotional prosodies in spoken words—happy, angry, sad, and neutral and the potential age and sex effects. Infants’ preferential looking times showed that they listened longer to the affective than the neutral voices, especially the happy and sad speech. Significant interaction effects were observed between emotion category and acoustic parameters of vocal emotion, but there were no main effects of age and sex. The second study employed a roving multi-feature oddball paradigm to record infants’ neurophysiological responses to these three basic affective prosodies against the neutral one. Infants showed distinct mismatch responses (MMRs) to different emotions in both early (100-200 ms) and late (300-500 ms) time windows, indicating their ability to extract affective speech patterns and detect emotional prosody changes at the pre-attentive level. Age- and sex-related effects were observed in the MMR data, indicating a higher degree of sensitivity of the electrophysiological measures over the behavioral measures in the first study. In the third study, adult listeners completed the same emotional multi-feature oddball experiment. The adults showed a stronger mismatch negativity (MMN) to angry prosody and a stronger P3a to happy prosody. Gender differences continued to be observed in the adult MMN and P3a data outside attentional focus on the emotional prosody changes in spoken words. Together, the current dissertation provides empirical data on emotional processing in speech from a developmental perspective, and it has strong implications for future studies to address links between early socio-emotional development and language development in normal and clinical populations.