The effect of motor resource suppression on speech perception in noise in younger and older listeners: an online study

Speech motor resources may be recruited to assist challenging speech perception in younger normally hearing listeners, but the extent to which this occurs for older adult listeners is unclear. We investigated if speech motor resources are also recruited in older adults during speech perception. Specifically, if suppression of speech motor resources via sub-vocal rehearsal affects speech perception, compared to non-speech motor suppression (jaw movement) and passive listening.
Participants identified words in speech-shaped noise at signal-to-noise ratios (SNRs) from -16 to +16 dB in three listening conditions during which participants: (1) opened and closed their jaw (non-speech movement); (2) sub-vocally mimed ‘the’ (articulatory suppression); (3) produced no concurrent movement (passive listening). Data from 46 younger adults (M age = 20.17, SD = 1.61, 36 female) and 41 older adults (M age = 69, SD = 5.82, 21 female) were analysed.
Linear mixed effects modelling investigated the impact of age, listening condition, and self-reported hearing ability on speech perception (d' prime). Results indicated that speech perception ability was significantly worse in older adults relative to younger adults across all listening conditions. A significant interaction between age group and listening condition indicated that younger adults showed poorer performance during articulatory suppression compared to passive listening, but older adults performed equivalently across conditions. This finding suggests that speech motor resources are less available to support speech perception in older adults, providing important insights for auditory-motor integration for speech understanding and communication in ageing.