Japanese learners’ speech errors may stem from morphological ambiguity, not just mispronunciation, offering fresh insights for language teaching

A recent study explores how Japanese learners of French produce ambiguous speech errors. Using a specialized assessment tool, researchers found that many mistakes once considered purely “phonetic” may actually be rooted in morpholexical misunderstanding, and vice-versa. The findings offer teachers valuable guidance for improving pronunciation pedagogy and error correction. This work opens new possibilities for assessing ambiguity in second-language speech and better understanding the interplay between sound and meaning in learning French.

Ambiguous speech production is a common challenge for learners of a second language (L2), but identifying whether the problem lies in pronunciation or deeper linguistic processing is not always straightforward. A new study conducted by Professor Sylvain Detey from Waseda University, with Dr. Verdiana De Fino from IRIT, UT3, University of Toulouse & Archean Labs, France, and Dr. Lionel Fontan, Head of Archean Labs, France, sheds light on this distinction. Their study was published on October 30, 2025, in the journal Language Testing in Asia.

The researchers sought to determine whether ambiguous speech errors made by Japanese learners of French could be better categorized through a combined phonetic and morpholexical assessment approach. By “morpholexical,” they refer to errors related to the way learners select and form words—such as choosing the correct verb ending, preposition, or gender marker—rather than just pronunciation mistakes. They designed an experimental protocol where learners’ utterances were evaluated by native French speakers for perceived ambiguity between word forms.

Using an innovative rating method and perceptual analysis, the team explored how certain cues in speech, such as vowel quality or gender-marking consonants, can lead to multiple interpretations. The results revealed that ambiguity in L2 speech cannot always be explained by phonetic inaccuracy alone; rather, morphological processing plays a significant role, especially when learners attempt to utter complex word forms or inflectional patterns.

“Our findings indicate that some speech errors stem not only from misarticulation but also from confusion at the morpholexical level,” says Prof. Detey.

The study provides empirical evidence that calls for a shift in how L2 pronunciation and lexical access are taught. Instead of isolating pronunciation drills from vocabulary and morphology exercises, educators may need to integrate them more holistically. Such integration could help learners overcome the hidden ambiguities that occur when sound and meaning interact.

Prof. Detey adds, “Our approach bridges pronunciation, grammar, and vocabulary, as well as oral and written modalities, encouraging teachers to interpret students’ speech errors not as random slips, but as windows into their mental lexicon.”

Beyond its immediate pedagogical relevance, the study also opens new avenues for linguistic testing and automated speech assessment. By identifying the boundary between phonetic and morpholexical causes of ambiguity, language researchers can refine diagnostic tools for second-language learners and design adaptive feedback systems for pronunciation software.

Ultimately, this pilot study underscores the importance of using ambiguity as a revealing lens into how learners process a new language. The authors hope their framework will guide further interdisciplinary research that merges phonetics, psycholinguistics, and pedagogy to enhance communication competence in foreign language education.

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Reference
Title of original paper: Phonetic or morpholexical issues in L2 speech? A pilot study of ambiguity assessment for pedagogical purposes among Japanese learners of French

Journal: Language Testing in Asia

DOI: 10.1186/s40468-025-00394-5

Authors: Sylvain Detey¹, Verdiana De Fino^2,3 and Lionel Fontan³

Affiliations
¹Faculty of International Research and Education, Waseda University, Japan
²IRIT, UT3, Université de Toulouse, France
³Archean Labs, France

About Waseda University
Located in the heart of Tokyo, Waseda University is a leading private research university that has long been dedicated to academic excellence, innovative research, and civic engagement at both the local and global levels since 1882. The University has produced many changemakers in its history, including eight prime ministers and many leaders in business, science and technology, literature, sports, and film. Waseda has strong collaborations with overseas research institutions and is committed to advancing cutting-edge research and developing leaders who can contribute to the resolution of complex, global social issues. The University has set a target of achieving a zero-carbon campus by 2032, in line with the Sustainable Development Goals (SDGs) adopted by the United Nations in 2015.

To learn more about Waseda University, visit https://www.waseda.jp/top/en

About Professor Sylvain Detey from Waseda University
Dr. Sylvain Detey is a Professor of Applied Linguistics and French Studies and currently the Dean of the Graduate School of International Culture and Communication Studies (GSICCS) at Waseda University, Japan. His core research areas are applied phonology, corpus linguistics, psycholinguistics, sociolinguistics, and French language studies. He focuses specifically on how the interaction between phonetic and lexical features impacts second-language acquisition. Dr. Detey has been teaching Applied Linguistics and French Studies in Japan for 20 years and he is co-director of the international Phonology of Contemporary French (PFC) research project, leveraging technology for the documentation and pedagogical use of spoken French corpora. He has been collaborating for many years with Dr. Lionel Fontan, Head of Archean Labs (France), on AI-oriented educational projects. In 2023, Dr. Detey was honored as a Knight in the Order of the Academic Palms by the French Republic.