Factors of age, temporal auditory processing, and speech-in-noise understanding performance in the McGurk effect

The McGurk effect is an illusion in which a third speech stimulus (/da/, fusion response) is perceived when incongruent auditory (/ba/) and visual (/ga/) cues are presented simultaneously. The frequency of fusion responses reflects susceptibility to the McGurk effect (MGD) and provides insight into audiovisual multisensory integration (AVMI) capacity. However, MGD shows substantial interindividual variability, and the underlying factors remain unclear. This study aimed to (i) determine whether MGD differs between age groups, (ii) examine its relationship with age, temporal auditory processing, and speech-in-noise (SIN) performance, and (iii) assess the predictive value of these variables on MGD. Sixty-four individuals aged 19–35 and 56+ years, all with normal hearing and normal (or corrected) vision, participated in a cross-sectional design. Hearing thresholds were measured using pure-tone audiometry (0.125–8 kHz, PTA) and extended high-frequency audiometry (10–16 kHz, EHF). Temporal auditory processing was evaluated using the Frequency Pattern Test (FPT), Duration Pattern Test (DPT), and Random Gap Detection Test (RGDT). SIN performance was assessed via the Turkish HINT. MGD was measured in three sessions (auditory-only, visual-only, audiovisual) using McGurk stimuli developed for the study. PTA and EHF thresholds were significantly higher in the older group. While FPT and DPT scores were higher in the younger group, differences were not significant. RGDT thresholds at 500 and 2000 Hz were significantly higher in older adults and positively correlated with age. Turkish HINT results showed better performance in the younger group across both right (NR) and left (NL) noise conditions and composite scores. MGD was significantly higher in the older group and moderately correlated with age. MGD varied from 0% to 100%. Fusion (/da/) responses were more frequent in older adults, while visual (/ga/) responses dominated among younger participants. MGD was negatively correlated with RGDT thresholds at 500 and 2000 Hz, and positively with HINT NR scores. A regression model including age, gender, and RGDT 2000 Hz significantly explained 42% of MGD variance. Findings indicate that temporal resolution and speech-in-noise (SIN) abilities decline with age, while susceptibility to the McGurk effect (MGD) increases. This increase may be attributed to the reduced reliability of auditory input with aging, supporting the view that audiovisual multisensory integration (AVMI) operates as a compensatory mechanism. As a simple and easily applicable phenomenon that provides insight into AVMI, MGD holds potential as a clinical assessment tool, particularly in audiology and special education fields.