What contributes to fluent L2 speech? Examining cognitive and utterance fluency link with underlying L2 collocational processing speed and accuracy

Second language (L2) fluency research has suggested that a range of linguistic knowledge and processing speed serve as cognitive fluency (CF) underlying L2 utterance fluency (UF). Building on prior CF-UF link studies, this study explored L2 collocational processing speed and accuracy as underlying CF measures. This study also explored the phrasal frequency effect on the relationship between collocational processing speed and UF to test whether the processing speed of higher-frequency collocations is more strongly related to UF. A total of 108 Japanese university students completed a phrasal acceptability judgment task with adjective–noun collocations pooled from the Academic Collocation List. Speech was elicited in an argumentative speech task, and UF measures were computed based on speed, breakdown, and repair fluency. The results revealed that the collocational processing speed was weakly tied to articulation rate and mid-clause and end-clause silent pause ratio (rho = |.271–.322|), while the collocational processing accuracy was weakly to moderately tied to most UF measures except filled pause ratio (rho = |.281–.368|). The collocation frequency moderated the relationship between the processing speed and UF, suggesting that high-frequency collocations served as a proxy for automaticity in speech production. Implications for CF-UF link research are discussed.