The Cardiovascular Response During Speech Reception

Hearing loss is a widespread and significant problem, resulting in reduced quality of life and diminished communication abilities for those affected. A common complaint raised by individuals with hearing loss is that listening requires substantial effort. As a result, researchers have sought ways to quantify listening effort, with physiological measures being a growing area of focus. Of the different physiological measures reported to index listening effort, cardiovascular measures hold potential due to their ability to be measured in an ambulatory and unobtrusive manner from individuals in their daily lives. Despite these benefits, past literature regarding cardiovascular measures during speech reception was relatively sparse, and study methods, measures and findings were inconsistent. This thesis aimed to contribute to addressing this gap in knowledge, with two overall aims. The first was to apply cardiovascular measures during speech-in-noise tasks of varying task demand. This was achieved by presenting speech at different signal-to-noise ratios (SNRs) or different task complexities, i.e., a single or dual dichotic listening paradigm. During speech reception, listening effort was indexed by different cardiovascular parameters, including pre-ejection period (PEP), heart rate variability (HRV), heart rate, blood pressure, pulse arrival time and blood volume pulse amplitude . These measures have been reported in the literature to reflect effort but had not necessarily been applied during listening before. Notably, cardiovascular measures and pupil measures were simultaneously applied and analysed using a novel classification approach. The second aim of this thesis was to explore the impact of different manipulations of success importance during listening. Success importance refers to the value that the listener places on successfully completing a listening task. Combined with task demand, success importance is known to moderate effort investment. Success importance was manipulated by providing performance-based monetary reward, changing the social context or by the presence or absence of virtual agents who provided performance feedback. The results of this thesis suggest that PEP, blood pressure and heart rate are the most sensitive cardiovascular measures during speech-in-noise tasks. These measures indicate increased cardiovascular reactivity in conditions with relatively high auditory task demand and when observed by others. The data within this thesis also suggest that more information may be obtained by looking at the cardiovascular response at shorter rather than longer timescales, for example, during sentence presentation which lasts several seconds, rather than across a whole block of sentences, lasting minutes. In particular, heart rate may fluctuate within a sentence , providing useful information about task demand over shorter intervals. Next, the studies within this thesis suggest that a larger range of task demand levels are more likely to yield measurable effects in cardiovascular measures. This thesis provides new insights into the cardiovascular response during speech reception. It builds upon and adds to the existing literature in the field, including novel measures (e.g., applying PEP during speech reception), study designs (e.g., incorporating virtual reality agents who provided live performance feedback) and analysis methods (e.g., combining different cardiovascular and pupil measures using classification ). Finally, this thesis suggests future avenues for research in this area and provides potential clinical benefits and applications of cardiovascular measures during listening measures, for instance, as a clinical diagnostic outcome measure, a data logging tool within hearing devices or for directing automatic control of hearing aid settings.