Shifts in Maximum Audiovisual Integration with Age.

Listeners attempting to understand speech in noisy environments rely on visual and auditory processes, typically referred to as audiovisual processing. Noise corrupts the auditory speech signal and listeners naturally leverage visual cues from the talker's face in an attempt to interpret the degraded auditory signal. Studies of speech intelligibility in noise show that the maximum improvement in speech recognition performance (i.e., maximum visual enhancement or VEmax), derived from seeing an interlocutor's face, is invariant with age. Several studies have reported that VEmax is typically associated with a signal-to-noise (SNR) of -12 dB; however, few studies have systematically investigated whether the SNR associated with VEmax changes with age. We investigated if VEmax changes as a function of age, whether the SNR at VEmax changes as a function of age, and what perceptual/cognitive abilities account for or mediate such relationships. We measured VEmax on a nongeriatric adult sample (N=64) ranging in age from 20 to 59 years old. We found that VEmax was age-invariant, replicating earlier studies. No perceptual/cognitive measures predicted VEmax, most likely due to limited variance in VEmax scores. Importantly, we found that the SNR at VEmax shifts toward higher (quieter) SNR levels with increasing age; however, this relationship is partially mediated by working memory capacity, where those with larger working memory capacities (WMCs) can identify speech under lower (louder) SNR levels than their age equivalents with smaller WMCs. The current study is the first to report that individual differences in WMC partially mediate the age-related shift in SNR at VEmax.