Phonotactic constraints on word-initial structures vary across languages: Slavic languages permit a wide range of sound sequences, while English prohibits stop-stop clusters and Japanese restricts any obstruent sequences. To examine the perceptual challenges faced by English monolinguals and English-speaking learners of Japanese due to acoustic similarities between native and non-native phonotactic patterns, we conducted a syllable counting experiment using non-words that mimic the phonotactic patterns of English, Japanese, and Slavic languages (e.g., /putata/, /pu̥tata/, and /ptata/). Our findings revealed that English monolinguals perceive Japanese-like tokens as having three syllables less often compared to Slavic-like sequences, indicating that the acoustics of linguistic input modulate the perception of sequences unattested in native phonotactics. Conversely, learners of Japanese showed sensitivity to underlying voiceless vowels, reflecting their integration of acoustic details with a learned phonotactic grammar that prohibits stop-stop onsets. However, exposure to the acoustics of Japanese voiceless vowels did not improve L2 listeners’ ability to perceive the Slavic-like clusters without an epenthetic vowel, suggesting that the acquired phonotactic constraint modulates the perception of acoustic input for L2 learners. Overall, the study underscores the intricate role of linguistic experience, providing insights for future research on L2 speech perception.

This paper critically examines the exclusive use of the relative frequency of subordinate clauses as a measure of syntactic complexity in Second Language Acquisition (SLA) L2 acquisition and as an indicator of Second Language (L2) development. Following Lambert & Kormos (2014), it is argued that it is important to also take into account: (i) different subordinate clause types, (ii) item-based frequencies, and (iii) text genre. Longitudinal written data was collected among 21 Dutch-speaking foreign language learners of Swedish. Based on these data, the study shows that the subordination ratio (a common measure for syntactic complexity) alone was found to be insufficient as an indicator of syntactic complexity and L2 development, as hardly any significant differences were observed in the subordination ratios of the learners and native speakers. The study shows that other aspects are also relevant in determining the learners’ level of syntactic complexity as well as their L2 development, such as the internal structure and context of subordinate clauses, subordinate clause types, and especially the type-token ratio of subordinators used. The results showed a significant negative correlation between the subordination ratio of texts and the type-token ratio of subordinators. The aim of the study is to acknowledge the variation in the learners’ use of subordinate clause, in addition to the general subordination ratio, in order to arrive at a more nuanced view of syntactic complexity in second language acquisition.