Clear speech provides insight into L2 category formation: Evidence from French front rounded vowels

This study investigates the clear-speech productions of second-language learners of French. A group of L1 American English L2 French learners and a group of L1 French speakers interacted with a faux computer program that elicited clear- and casual-speech productions. The productions were acoustically analyzed to understand what cues were modified in clear speech. Results show that learners lowered F2 (i.e., produced a more posterior vowel) for front rounded vowels in clear speech but did not modify F3 (i.e., did not manipulate rounding) to the same extent as L1 speakers. In addition, higher proficiency was associated with lowered F3 in baseline productions but not in clear productions for high front unrounded vowels [i] and [e], which had the effect of increasing the baseline-clear F3 difference for learners with more French experience. Results suggest clear speech can be a useful methodology for better understanding L2 category formation. The findings presented here provide evidence for phonetically grounded models of L2 acquisition, revealing that category development proceeds through vowel-specific acoustic strategies and asymmetric cue reweighting rather than abstract feature transfer. Additionally, L2 development involves adding target-like acoustic strategies while not fully suppressing the learners’ L1 transferred strategies.