Lexical richness in the speech of Mandarin Chinese for L2 learners

Why the Words We Choose in a New Language Matter

When adults learn to speak a new language, success is not just about avoiding mistakes—it is also about how rich and varied their words are. This study looks at how English-speaking adults learning Mandarin Chinese use vocabulary when they speak, and how that vocabulary relates to their speaking test scores. By examining tens of thousands of spoken words with modern computational tools, the researchers uncover which kinds of words and word patterns best signal strong spoken Chinese, and how these patterns differ from both written Chinese and from other languages such as English.

Looking Closely at Learners Speaking Chinese

The researchers analyzed speech from 140 adults whose first language is English and who began learning Chinese as adults. All of them took the same standardized speaking exam in Mandarin, and their performances were scored by trained native-speaker teachers. To keep things fair, the team controlled the length of each speech sample so that every learner produced about the same number of words. This allowed them to focus on how words were used—rather than how much someone spoke—when exploring what separates higher- and lower-scoring speakers.

Different Ways to Measure Word Use

To capture what they call “lexical richness,” the authors broke vocabulary use into three main aspects. First, they measured diversity: how many different words a speaker uses relative to the total number of words. Second, they examined sophistication: how often speakers tap into more advanced, less common vocabulary instead of everyday words. Third, they calculated density: how many meaning-carrying words (such as nouns and verbs) appear compared with more grammatical words (like pronouns or small particles). Within each aspect, the team used a suite of detailed indices, many of which were originally designed for research on English, to see whether these tools also work well for Mandarin Chinese.

What Makes Spoken Chinese Sound More Advanced

The analysis shows that speakers who earn higher scores tend to use a wider range of different words, confirming that diversity matters. Certain mathematical versions of diversity measures, which smooth out the effect of text length, proved especially powerful for Chinese speech. The study also finds that not all word types are equally important. In Mandarin, the variety of adverbs—words that modify actions or qualities—and the diversity of verbs are particularly strong signals of better speaking. Likewise, measures of how heavily a learner relies on meaning-rich words, rather than repeating the same ones, help explain differences in oral test scores. Together, all of the vocabulary measures the team considered could account for just over 40 percent of the variation in speaking performance.

How Chinese Differs from English and from Writing

A key discovery is that the same indices do not behave the same way across languages or between speaking and writing. In English, sophisticated low-frequency words and certain verb measures are strong predictors of quality, especially in writing. In spoken Mandarin, however, high-frequency words and specific patterns of function words—especially small auxiliary particles that carry tense or aspect—matter more, while some English-based measures do not fit as well. The study also shows that indices which work for written Chinese, such as those based on pronouns, can be less informative for speech, where pronouns are often omitted and speakers favor efficiency over explicitness.

What This Means for Learners and Teachers

Overall, the findings suggest that for adult learners of Mandarin Chinese, sounding more proficient is less about forcing rare words into conversation and more about using a broad, flexible mix of common verbs, adverbs, and key function words. The study highlights that vocabulary assessment tools developed for English cannot simply be copied over to Chinese without adjustment. By identifying which word patterns best reflect speaking ability, this research can guide teachers to emphasize particular word types in class and can help developers build more accurate automated scoring systems for Chinese speaking tests. For learners, it underscores a practical message: mastering how to use everyday words in varied and nuanced ways is central to speaking Chinese well.

Citation: Hao, Y., Lin, J., Yang, Q. et al. Lexical richness in the speech of Mandarin Chinese for L2 learners. Humanit Soc Sci Commun 13, 437 (2026). https://doi.org/10.1057/s41599-026-06566-9

Keywords: Mandarin second language, lexical richness, spoken proficiency, word classes, language assessment