Perceptual consequences of native and non-native clear speech

Native talkers are able to enhance acoustic characteristics of their speech in a speaking style known as “clear speech,” which is better understood by listeners than “plain speech.” However, despite substantial research in the area of clear speech, it is less clear whether non-native talkers of various proficiency levels are able to adopt a clear speaking style and if so, whether this style has perceptual benefits for native listeners. In the present study, native English listeners evaluated plain and clear speech produced by three groups: native English talkers, non-native talkers with lower proficiency, and non-native talkers with higher proficiency. Listeners completed a transcription task (i.e., an objective measure of the speech intelligibility). We investigated intelligibility as a function of language background and proficiency and also investigated the acoustic modifications that are associated with these perceptual benefits. The results of the study suggest that both native and non-native talkers modulate their speech when asked to adopt a clear speaking style, but that the size of the acoustic modifications, as well as consequences of this speaking style for perception differ as a function of language background and language proficiency.