Effect of adult aging on pupillary response to auditory stimuli of varying levels of complexity

Abstract

Pupil dilation as a measure of listening effort has been well documented (Kuchinsky et al., 2013), as has the association between adult aging and increased effort in listening tasks (Wingfield et al., 2015). However, age-related differences in the dynamics of pupillary response over time while attending to auditory stimuli have received less study; nor has the nature of the pupillary response to simple stimuli (tones) versus more complex speech stimuli (words, sentences) been systematically explored. In this study we examined multiple parameters of young adult and older adult listeners’ changes in pupil size, including peak amplitude and latency to peak, elicited while making decisions in response to auditory stimuli that varied in acoustic or linguistic complexity. Results showed that the latency to peak pupil size was slower for older adults and for increasingly complex stimuli. The shape of pupillary response curve also changed dramatically with the nature of the stimuli: attending to briefer stimuli (tones, words) resulted in a more peaked pupillary response curve than for sentence-length stimuli, which took a more complex form. These results suggest that both adult aging and stimulus complexity influence the dynamics of the pupillary response as an index of processing effort for acoustic stimuli.