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.
