Exploring the nuances of reduction in conversational speech: lexicalized and non-lexicalized reductions

In spoken language, a significant proportion of words are produced with missing or underspecified segments, a phenomenon known as reduction. In this study, we distinguish two types of reductions in spontaneous speech: lexicalized reductions, which are well-documented, regularly occurring forms driven primarily by lexical processes, and non-lexicalized reductions, which occur irregularly and lack consistent patterns or representations. The latter are inherently more difficult to detect, and existing methods struggle to capture their full range.

We introduce a novel bottom-up approach for detecting potential reductions in French conversational speech, complemented by a top-down method focused on detecting previously known reduced forms. Our bottom-up method targets sequences consisting of at least six phonemes produced within a 230 ms window, identifying temporally condensed segments, indicative of reduction.

Our findings reveal significant variability in reduction patterns across the corpus. Lexicalized reductions displayed relatively stable and consistent ratios, whereas non-lexicalized reductions varied substantially and were strongly influenced by speaker characteristics. Notably, gender had a significant effect on non-lexicalized reductions, with male speakers showing higher reduction ratios, while no such effect was observed for lexicalized reductions. The two reduction types were influenced differently by speaking time and articulation rate. A positive correlation between lexicalized and non-lexicalized reduction ratios suggested speaker-specific tendencies.

Non-lexicalized reductions showed a higher prevalence of certain phonemes and word categories, whereas lexicalized reductions were more closely linked to morpho-syntactic roles. In a focused investigation of selected lexicalized items, we found that “tu sais” was more frequently reduced when functioning as a discourse marker than when used as a pronoun + verb construction. These results support the interpretation that lexicalized reductions are integrated into the mental lexicon, while non-lexicalized reductions are more context-dependent, further supporting the distinction between the two types of reductions.