Although fluency constitutes an essential component of second language (L2) proficiency, there are mixed results and gaps in the literature on how L2 speakers’ fluency differs from fluent speech production in a first language (L1). The research reported in this article investigated utterance fluency and cognitive fluency of L1 English speakers and Korean learners of L2 English by eliciting and comparing quantitative evidence from temporal measures and qualitative evidence from stimulated recall responses. In addition, the L2 speaker group's proficiency was measured by an in‐house institutional test so as to inspect how L2 fluency measures correlated to varying proficiency. The L1 and L2 speakers were different in speed, length of run, and silent pauses. In particular, a striking group difference in silent pause rate within a clause was found, consistent with the claim that pauses within clauses reflect processing difficulties in speech production. Different qualitative patterns in the stimulated recall responses by the lower and higher proficiency learners are discussed in relation to Ullman's declarative/procedural model and Segalowitz's fluency vulnerability points in L2 speech production.

Given that utterance fluency in a second language (L2) is associated with not only L2 cognitive fluency but also utterance fluency in the first language (L1), the study examined to what extent different measures of L2 utterance fluency can be explained by L2-specific cognitive fluency and/or the corresponding L1 utterance fluency measures. Utterance fluency measures on speed, breakdown, and repair phenomena and cognitive fluency measures including speed of lexical retrieval, syntactic encoding, and articulation were collected in the L1 and the L2 from 44 Chinese learners of English. The results show that most L2 utterance fluency measures are accounted for by the combination of L2-specific cognitive fluency measures and the equivalent L1 utterance fluency measure, whereas the number of mid-clause silent pauses and corrections, and mean syllable duration are largely explained by L2-specific cognitive measures, suggesting that they reflect L2-specific knowledge and cognitive skills. In contrast, mean silent pause duration and the number of filled pauses are mainly explained by the corresponding L1 utterance fluency measures.

Speech disfluency in first language (L1) and second language (L2) is not only quantitatively different (e.g., number and length of pauses) but also qualitatively different (e.g., distribution of pauses); however, how pause distributions in L1 and L2 affect judgments of perceived fluency is unclear. The study examined the relationship between pause phenomena and perceived fluency using two experiments. Experiment 1 investigated the relative contributions of frequency, length, and distribution of silent pauses to perceived fluency of L2 speech. Experiment 2 tested causal effects of pause location on perceived fluency of L1 and L2 speech using phonetic manipulations. Findings suggest a significant role of pause location in perceived fluency. In Experiment 1, silent pause rate within a clause demonstrated the strongest correlation with L2 fluency ratings, and in Experiment 2, perceived fluency of L1 and L2 speech was influenced by pause location. The findings suggest that listeners seem to be sensitive to pause location and to understand that pauses within clauses tend to reflect reduced cognitive fluency.

Listeners often perceive illusory vowels when presented with consonant sequences that violate phonotactic constraints in their language. Previous research suggests that the phenomenon motivates speech-perception models that incorporate surface phonotactic information and the acoustics of the speech tokens. In this article, inspired by Bayesian models of speech perception, we claim that the listener attempts to identify target phonemic representations during perception. This predicts that the phenomenon of perceptual illusions will be modulated not only by surface phonotactics and the acoustics of the speech tokens, but also by the phonological alternations of a language. We present the results of three experiments (an AX task, an ABX task and an identification task) with native Korean listeners, and native English listeners as a control group, showing that Korean listeners perceive different sets of illusory vowels in different phonological contexts, in accordance with the phonological processes of vowel deletion and palatalisation in the language.

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