Second Language Speakers' Use and Maintenance of Clear Speech in Natural Conversations

This study examined whether second language (L2) speakers of English spontaneously modify their speech features, such as F0, F0 range, speech rate, and vowel duration, to enhance intelligibility when interacting with different types of conversation partners. We analyzed natural conversational data that were collected using a Diapix task, in which L2 speakers interacted with native speakers, L2 speakers who shared the same L1, and L2 speakers with different L1 backgrounds. The results showed that L2 speakers exhibited a significantly greater F0 range when speaking to L2 interlocutors with different L1 backgrounds compared to native speakers, suggesting that they have used more exaggerated articulation for listener-oriented purposes. No significant differences were found in other speech features, such as median F0, speech rate, and vowel duration. In addition, L2 speakers' speech patterns did not change over time. Overall, our findings suggest that L2 speakers exhibit certain features of clear speech in conversation with another non-native speaker who has a different L1 background. We suggest that this may be due to L2 speakers' unfamiliarity with a foreign accent, leading them to assume that their interlocutor also experiences comprehension difficulties and to hyperarticulate their speech to enhance mutual understanding.