Listening effort under different rates of speech

Abstract

Listening effort, the cognitive resources allocated to understand spoken language, is a critical issue in communication under adverse listening environments. The present study investigated how listening effort would be affected by differing speech tempos. The experiment involved 23 native Korean adults with normal hearing, who were presented with linguistically complex Korean sentences at five different speeds (35%∼200% of original time). The cognitive load associated with listening under various speech rate conditions was quantified employing a dual-task paradigm, where the increased listening effort would impair the performance on an additional cognitive task. Participants listened to the sentences while performing an n-back task and then repeated back the sentence they heard. The results found a significant effect of speech rate on the n-back task, with lower accuracies in the faster speech conditions. The additional task also increased the overall cognitive load of sentence recognition, leading to various speech errors, such as the omission of key content words, unnecessary additions, and substitutions with similar words. This demonstrates that increased cognitive load during listening impairs speech processing at multiple levels (e.g., semantic processing, retention of words in working memory), emphasizing the need to adjust speech tempos for better understanding and comfort in listeners.