What did you said? Acoustic challenge and hearing loss induce shifts in predictive and integrative processing in younger and older listeners during speech comprehension

When listening to acoustically challenging speech, listeners may have to compensate by shifting their cognitive strategies such as how they use prior context. This shift may depend on the age and hearing acuity of the listener. In the current study, younger adults with normal hearing (N = 48; Exp 1) and older adults with varying hearing acuity (N = 80; Exp 2), listened in quiet and in noise to contextually constraining sentences that ended in an expected word, an unexpected word, or a morphosyntactic violation of the expected word. We recorded EEG and extracted event-related potentials (ERPs) to target words. For younger adults, we observed that the syntactic P600—a component linked to controlled integrative processes—was reduced when listening to speech in background noise. In contrast, an ERP response more strongly yoked to predictive processing, the late frontal response, was present in noise, suggesting that acoustic challenge did not impair predictive processing. For older adults with normal hearing, we observed a small prediction-related ERP response and a robust P600 response in quiet. In noise, the integration-related P600 response to syntactic violations was reduced while the increased syntactic N400 effect increased, suggesting a shift from an integrative mode to reliance on lexical predictions. In quiet, a similar shift towards reduced integration and increased prediction was observed with increasing hearing loss, but these prediction-related effects were severely reduced among older adults with hearing loss when speech was presented in noise, suggesting auditory limits to compensatory reliance on contextual prediction. Collectively, these results suggest that listeners show adaptive shifts between integrative and predictive processing modes as a function of age, acoustic challenge, and hearing acuity.