Age and sex effects in emotional prosody processing revealed in infants' mismatch responses but not in preferential looking time

Abstract

Emotional prosody is crucial in early communication, but the developmental trend and the emergence of sex differences in infants’ emotional processing remain unclear. This report compared 46 infants’ behavioral and neurophysiological responses to four vocal emotions (happy, angry, sad, and neutral). We used a central fixation paradigm to measure infants’ listening times to different emotions and a multi-feature oddball paradigm with electroencephalography (EEG) recordings to measure infants’ mismatch responses (MMRs) to vocal emotional changes. We modified both paradigms by including non-repeating words within each emotion, enforcing infant listeners to respond to the overarching emotional prosodic category. We only observed age and sex effects in infants’ MMRs. Older infants showed more negative MMRs to happy and sad voices than younger infants, but more positive MMRs to angry voices. Female infants showed more positive MMRs at a later time window than male infants across all emotional changes, indicating an emotion-general sex effect. The behavioral study showed longer listening times for happy and sad prosodies across age and sex. The findings indicate that neurophysiological measurement may be more sensitive in capturing age and sex effects in early emotional prosody perception when complex speech materials are used.