Real-Time Conversation Comprehension in Younger and Older Adults: The Effects of Noise, Visual Speech, Speaker...

This study investigated older and younger adults' conversational speech understanding using an established topic monitoring task to assess real-time semantic processing. Twenty-three younger adults (mean age = 26.5 years) and 19 older adults (mean age = 71.3 years) monitored for topic targets in 24 dialogues (2-3 minutes each). The impact on monitoring response time and accuracy of two message-level factors (when speakers switch; contextual predictability) was assessed while manipulating two signal-level factors (presentation modality; noise level). Results showed that presentation modality affected response times, with faster correct responses for audio-visual versus audio-only presentation, an effect that interacted with age (older adults had a larger visual speech benefit). Noise (0 dB SNR) increased response times and decreased accuracy compared to presentation in quiet. A speaker switch delayed response time to the first target after the switch compared to non-switch targets. When the target occurred relatively soon after a speaker switch, older adults showed a significant switch cost, whereas younger adults did not. Targets that were more predictable from context (low surprisal) had faster response times. In the most challenging listening condition (Audio-only presentation in noise), the effect of contextual predictability for older adults was marginally larger than for younger adults, suggesting greater use of context. These findings highlight the utility of the topic monitoring task for probing conversational speech comprehension across the lifespan.