Building on the extensive work conceptualizing, developing, and validating foreign language aptitude for successful second language acquisition (e.g., Skehan, 2015, in Applied Linguistics), the current project expounded the cognitive abilities relevant and instrumental to adult Japanese classroom learners’ pronunciation attainment of English /ɹ/. The speech production of 50 Japanese participants was elicited, acoustically analyzed, and linked to different aspects of their aptitude profiles (phonemic coding, associative memory, and sequence recognition). Whereas those with higher phonemic coding demonstrated better performance in a relatively easy dimension of English /ɹ/ pronunciation (lower F2 for tongue retraction), those with greater associative memory demonstrated more advanced performance in the relatively difficult dimensions of English /ɹ/ pronunciation (longer transition duration for phonemic length; lower F3 for labial/alveolar/pharyngeal constrictions). The role of incidental learning aptitude (i.e., sequence recognition) remained unclear. The findings here indicate that explicit aptitude related to phonological analysis and memory may play a key role in predicting the incidence of advanced second language segmental proficiency attainment in classroom settings.

The current project examined whether and to what degree continued L2 input, operationalized as length of residence (LOR), and age of acquisition (AOA), defined as the first intensive exposure to the target language, can be predictive of adult Japanese learners’ production of word-initial English /ɹ/. Data were collected from 65 participants, consisting of three groups of Japanese learners of English (n = 13 for Short-, Mid-, and Long-LOR groups, respectively) and two groups of baseline speakers (n = 13 for Japanese- and English-Baseline groups, respectively). Their production of /ɹ/ was elicited via three oral tasks (i.e., word reading, sentence reading, timed picture description). Acoustic analyses were carried out along four dimensions: third formant (F3), second formant (F2), first formant (F1) frequencies, and formant transition duration. The results demonstrated that (a) all learners reached native-like proficiency with respect to the use of existing cues (F2, transition duration) within approximately one year of LOR, (b) their performance was negatively related to AOA to some degree, and (c) longer LOR was predictive of the development of the new cue (F3). These results suggest that late L2 speech sound acquisition and proficiency may be characterized by different levels of phonetic processing.