Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Neuroscience

Supervisor

Dr. Ingrid S. Johnsrude

2nd Supervisor

Dr. Björn Herrmann

Affiliation

Rotman Research Institute

Co-Supervisor

Abstract

Degraded speech encoding as a result of hearing loss increases cognitive load and makes listening effortful. Standard hearing assessment does not capture this cognitive impact of hearing impairment. Speech-in-noise testing measures intelligibility for isolated sentences that are typically not engaging and lack meaningful context. These materials may not capture the processes involved in everyday listening situations, in which people are often intrinsically motivated to comprehend the speech they are hearing. The current study explored a novel approach using natural, spoken stories. We first characterized time courses of executive load during story listening in young individuals with normal hearing using a reaction time (RT) task. We then computed correlations between executive load time courses (operationalized as reaction times) to quantify their reliability. Reaction-time time courses were significantly correlated across participants, suggesting consistent cognitive recruitment across individuals. Synchronization of RTs across participants was related to ratings of story enjoyment, but not absorption, suggesting that enjoyment, one key facet of engagement, predicts the degree to which a story’s cognitive demands are experienced similarly by listeners. Correlated executive load time courses among healthy individuals may be sensitive to abnormal mental states: divergence from the canonical time courses characterized here could serve as a sensitive tool for characterizing listening effort.

Summary for Lay Audience

Many older people experience difficulty understanding speech in minimal background noise, and often report listening to be effortful. Increases in listening effort are associated with declines in quality of life and mental health, but clinical tests of speech perception are not sensitive to the effort patients report. Speech perception testing relies on standardized sentences that lack meaningful context. These tests may fail to capture the key cognitive processes that support listening in everyday environments, in which people are often motivated to comprehend the speech they listen to. In this study we explore a novel method of assessing listening using engaging spoken stories. Our findings suggest that the dynamics of cognitive processing during listening are consistent across individuals, and that the consistency of cognitive processing is related to story enjoyment. High consistency in cognitive processing among young people with normal hearing provides sensitivity to abnormal mental states, potentially enabling detection of people who find listening in background noise to be unusually effortful. Building on existing tests of speech perception, this research opens the door to methods of assessing listening effort that better capture the processes underlying listening in everyday environments.

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