The impact of spectral resolution on listening effort revealed by pupil dilation

Abstract

Poor spectral resolution is a consequence of cochlear hearing loss and remains arguably the primarily limiting factor in success with a cochlear implant. In addition to showing reduced success on word recognition compared to their normal-hearing peers, listeners with hearing impairment also are reported to exert greater effort in everyday listening, leading to difficulties at the workplace and in social settings. Pupil dilation is an index of cognitive effort in various tasks, including speech perception. In this study, spectral resolution was explicitly controlled for in listeners with normal hearing using a noise vocoder with variable number of processing channels. Pupil dilation during a sentence listening and repetition task revealed a systematic relationship between spectral resolution and listening effort; as resolution grew poorer, effort increased. Significant changes in listening effort belie the notion of “ceiling” performance in degraded conditions; listeners are able to achieve success in the face of signal degradation at least partly on behalf of extra effort required to listen. We provide a model by which interventions for clinical populations (e.g., processing strategies) can be evaluated on the basis of listening effort, beyond the conventional techniques of word and sentence recognition accuracy.