Mackersie Carol L, Cones Heather
School of Speech, Language and Hearing Sciences, San Diego State University, San Diego, California 92182-1518, USA.
J Am Acad Audiol. 2011 Feb;22(2):113-22. doi: 10.3766/jaaa.22.2.6.
The effects of noise and other competing backgrounds on speech recognition performance are well documented. There is less information, however, on listening effort and stress experienced by listeners during a speech-recognition task that requires inhibition of competing sounds.
The purpose was (a) to determine if psychophysiological indexes of listening effort were more sensitive than performance measures (percentage correct) obtained near ceiling level during a competing speech task, (b) to determine the relative sensitivity of four psychophysiological measures to changes in task demand, and (c) to determine the relationships between changes in psychophysiological measures and changes in subjective ratings of stress and workload.
A repeated-measures experimental design was used to examine changes in performance, psychophysiological measures, and subjective ratings in response to increasing task demand.
Fifteen adults with normal hearing participated in the study. The mean age of the participants was 27 (range: 24-54).
Psychophysiological recordings of heart rate, skin conductance, skin temperature, and electromyographic (EMG) activity were obtained during listening tasks of varying demand. Materials from the Dichotic Digits Test were used to modulate task demand. The three levels of task demand were single digits presented to one ear (low-demand reference condition), single digits presented simultaneously to both ears (medium demand), and a series of two digits presented simultaneously to both ears (high demand). Participants were asked to repeat all the digits they heard, while psychophysiological activity was recorded simultaneously. Subjective ratings of task load were obtained after each condition using the National Aeronautics and Space Administration Task Load Index questionnaire. Repeated-measures analyses of variance were completed for each measure using task demand and session as factors.
Mean performance was higher than 96% for all listening tasks. There was no significant change in performance across listening conditions for any listener. There was, however, a significant increase in mean skin conductance and EMG activity as task demand increased. Heart rate and skin temperature did not change significantly. There was no strong association between subjective and psychophysiological measures, but all participants with mean normalized effort ratings of greater than 4.5 (i.e., effort increased by a factor of at least 4.5) showed significant changes in skin conductance.
Even in the absence of substantial performance changes, listeners may experience changes in subjective and psychophysiological responses consistent with the activation of a stress response. Skin conductance appears to be the most promising measure for evaluating individual changes in psychophysiological responses during listening tasks.
噪声和其他竞争性背景对言语识别性能的影响已有充分记录。然而，关于在需要抑制竞争性声音的言语识别任务中，听众所经历的听力努力和压力的信息较少。
目的是（a）确定在竞争性言语任务中，听力努力的心理生理指标是否比接近上限水平时获得的性能指标（正确百分比）更敏感；（b）确定四种心理生理指标对任务需求变化的相对敏感性；（c）确定心理生理指标变化与压力和工作量主观评分变化之间的关系。
采用重复测量实验设计来检验随着任务需求增加，性能、心理生理指标和主观评分的变化。
15名听力正常的成年人参与了该研究。参与者的平均年龄为27岁（范围：24 - 54岁）。
在不同需求的听力任务期间，获取心率、皮肤电导率、皮肤温度和肌电图（EMG）活动的心理生理记录。使用双耳数字测试的材料来调节任务需求。任务需求的三个水平分别是单数字呈现给一只耳朵（低需求参考条件）、单数字同时呈现给两只耳朵（中等需求）以及一系列两个数字同时呈现给两只耳朵（高需求）。要求参与者重复他们听到的所有数字，同时记录心理生理活动。在每个条件之后，使用美国国家航空航天局任务负荷指数问卷获得任务负荷的主观评分。使用任务需求和会话作为因素，对每个指标完成重复测量方差分析。
所有听力任务的平均性能均高于96%。任何听众在不同听力条件下的性能均无显著变化。然而，随着任务需求增加，平均皮肤电导率和EMG活动显著增加。心率和皮肤温度没有显著变化。主观指标和心理生理指标之间没有强关联，但所有平均标准化努力评分大于4.5（即努力增加至少4.5倍）的参与者，其皮肤电导率均有显著变化。
即使在没有显著性能变化的情况下，听众可能会经历与应激反应激活一致的主观和心理生理反应变化。皮肤电导率似乎是评估听力任务期间心理生理反应个体变化的最有前景的指标。
