Researchers found that using everyday phrasal expressions boosts fluency perception more than rare phrases in foreign language speech

Fluency in a foreign language is often thought to be about speaking quickly and using advanced vocabulary. However, researchers from Waseda University reveal that speakers who use common, everyday expressions sound more fluent than those who rely on rare, complex words. The study highlights the importance of mastering familiar phrases to improve fluency perception, suggesting that learners should naturally incorporate common formulaic expressions in spontaneous speech.

Language learners often assume that using rare, complex vocabulary will make their speech sound more fluent. Research suggests that there is a close relationship between formulaic expression usage in speech and acoustic features of oral fluency. This implies that using formulaic expressions leads to faster articulation speed and fewer disruptions during speech. However, in terms of how listeners perceive speakers’ fluency, the role of formulaic expressions has been unclear.

To investigate this, Ph.D. student, Kotaro Takizawa and Research Assistant Professor Shungo Suzuki from Waseda University, Japan, analyzed speech from 102 Japanese speakers of English, each delivering an argumentative speech. They measured the use of bigram and trigram expressions (two- and three-word sequences) and had fluency judged by 10 experienced raters. The study controlled for key fluency metrics, including articulation rate, pauses, and self-corrections, to isolate the effect of formulaic expressions on fluency perception. This study was published online in the journal Studies in Second Language Acquisition on February 12, 2025.

The findings revealed that utterance fluency (smoothness of speech delivery) was the strongest predictor of fluency perception, accounting for 61% of the variance in ratings. However, high-frequency formulaic expressions added an extra 0.8% to fluency judgments, while rarer, more complex phrases had little to no effect.

The study also reveals that the key to sounding fluent is not about using sophisticated words; it is about using the right phrases. Their study shows that common, everyday expressions have a small but significant impact on how fluency is perceived, even when a factor like smoothness is accounted for. "We found that common, oft-used formulaic expressions, rather than rare, sophisticated ones, significantly influenced rater judgment of speakers’ fluency," said Takizawa.

Fluency plays a crucial role in language learning and assessment, especially in standardized tests like TOEFL and IELTS, where expert raters evaluate how natural and smooth a speaker sounds. Traditionally, fluency has been associated with speed and uninterrupted speech, but the role of formulaic expressions (common multi-word phrases) has been less clear. Previous studies suggested that these expressions help speakers communicate more smoothly, but few have examined how they influence fluency perception on their own.

Suzuki highlighted the practical implications: "It is generally observed that language teachers and learners tend to focus more on rare words or difficult phrases that sound more proficient. However, the current findings indicate that that should not necessarily be the focus, particularly if they want to improve their fluency perceived by others."

This research suggests that learners should shift their focus from advanced vocabulary to mastering everyday phrases that come naturally in conversation. For example, instead of saying "I agree the idea"—which sounds unnatural—learners should use "I agree with the idea." These common expressions are easy to find in textbooks and everyday conversations, making them more accessible for learners of all levels.

The study has significant implications for language testing, where fluency judgments can impact scores. It suggests that test-takers should focus on integrating natural phrasal expressions into their speech while maintaining the smoothness of their speech. Highlighting the importance of both aspects, "Our research shows that there is no denying that improving fluency in utterance contributes to good fluency judgment scores," noted Takizawa.

This study highlights the crucial role of common expressions in shaping how fluency is perceived, offering valuable insights for language learners and educators.

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Reference
DOI: https://doi.org/10.1017/S0272263125000051

Title of original paper: The role of multiword sequences in fluent speech: The case of listener-based judgment in L2 argumentative speech

Journal: Studies in Second Language Acquisition

Authors: Kotaro Takizawa¹, Shungo Suzuki²

Affiliations
¹Graduate School of Education, Waseda University, Japan
²Green Computing Systems Research Organization, Waseda University, Japan