Using pupillometry to investigate the better ear advantage

Abstract

The dichotic digit span (DDS) task involves listening to and repeating back strings of different digits that are presented to the right and left ears. Listeners with normal hearing typically show better recall of the digits that are presented to the right ear (called the ear advantage, or EA), for reasons that are not fully understood. Conventional measures of intelligibility are sometimes not sensitive enough to reveal a right EA, making it difficult to explore potential explanations for the effect (e.g., whether it is driven by attention or anatomical differences, etc.). In this study, we used pupillometry to investigate the EA because it has been shown to be able to detect subtle differences in speech processing (or listening effort) in cases that are not well distinguished by intelligibility scores. Pupillary responses to various conditions of the DDS test were measured in a group of people with no suspected hearing loss to establish baseline data. Results were at times variable within listeners, which opposes a strict anatomical basis for the EA. Interestingly, the responses showed a sustained period of effort after the end of the stimuli, suggesting the EA could involve working memory rather than the perceptual auditory system alone.