Abstract
Using behavioral evaluation of free recall performance, we investigated whether reverberation and/or noise affected memory performance in normal-hearing adults. Thirty-four participants performed a free-recall task in which they were instructed to repeat the initial word after each sentence and to remember the target words after each list of seven sentences, in a 2 (reverberation) × 2 (noise) factorial design. Pupil dilation responses (baseline and peak pupil dilation) were also recorded sentence-by-sentence while the participants were trying to remember the target words. In noise, speech was presented at an easily audible level using an individualized signal-to-noise ratio (95% speech intelligibility). As expected, recall performance was significantly lower in the noisy environment than in the quiet condition. Regardless of noise interference or reverberation, sentence- baseline values gradually increased with an increase in the number of words to be remembered for a subsequent free-recall task. Long reverberation time had no significant effect on memory retrieval of verbal stimuli or pupillary responses during encoding.
Highlights
Hearing-impaired (HI) people often report difficulty in comprehending speech in noisy or reverberant environments, whereas young adults with normal-hearing (NH) can reportedly cope with reverberant speech with a moderate amount of background noise [1,2].HI elderly and children are more vulnerable to the effects of reverberation than NH elderly and children [3]
We investigated the following hypotheses: (1) speech with long reverberation time (RT) may negatively affect recall performance in NH adults, even though speech is presented at a near-ceiling level, (2) speech in a noisy listening environment may negatively affect recall performance in NH adults, even though speech is presented at a near ceiling level, (3) recall performance may depend on the target word’s position in the list, which will be explained (4) pupil dilation response to each stimulus may tend to increase or decrease as a function of stimulus presentation order due to the increases in memory load and/or listening effort, and (5) these trends may be affected by the RT and/or background noise
In this study, which extends our prior work [20], we focused on the unfavorable effects of background noise and/or prolonged RT on recall performance, as well as pupil dilation responses for each stimulus in a list during the encoding period in a group of NH listeners
Summary
Hearing-impaired (HI) people often report difficulty in comprehending speech in noisy or reverberant environments, whereas young adults with normal-hearing (NH) can reportedly cope with reverberant speech with a moderate amount of background noise [1,2].HI elderly and children are more vulnerable to the effects of reverberation than NH elderly and children [3]. The Framework for Understanding Effortful Listening (FUEL) [4] defines listening effort as “the deliberate allocation of mental resources to overcome obstacles in goal pursuit when carrying out a [listening] task”, and suggests that signal-to-noise ratio (SNR) and reverberation time (RT) as transmission factors and indirect inputs via the cognitive capacity component. Reverberation distorts the signals reaching the ear and impedes selective auditory attention [6], and this detrimental impact on speech intelligibility and listening effort can be measured by speech transmission index [7,8,9], electro-dermal activity levels, and subjective ratings [10]. Xia et al (2018) [11] reported that both NH and HI listeners found it hard to recognize words in noise, showing degraded performance as a result of increased reverberation time
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