Effect of auditory precision on L2 speech learning is partially mediated by learning target and instruction form

The ability to learn a second language (L2), particularly novel speech sounds, varies significantly among individuals. Previous studies highlight the importance of auditory processing skills in L2 acquisition. However, the way auditory precision interacts with factors, such as the learning target (acoustic differences in sounds) and instruction form (types of instruction and feedback), remains to be further investigated. To explore this, we conducted a four-day classroom experiment with 80 adult Mandarin speakers learning Russian laryngeal contrasts: stops vs. fricatives. Participants were assigned to two groups receiving different instructions. One group received feedback focusing on word meaning, while the other group received instruction that emphasized both meaning and phonetic form with explicit instruction. Our findings reveal a complex interplay between auditory precision, learning target, and instruction form. Generally, superior auditory precision was associated with better speech learning outcomes across both types of instruction and consistently across learning targets. However, the three-way interaction presented a nuanced perspective. Results showed that learners with higher auditory precision benefited more from explicit instruction in their ability to perceive stop consonants; those with lower auditory precision also benefited, but to a lesser extent. This effect was not observed in the learning of fricatives. These results highlight the critical role of auditory processing in L2 learning, and suggest that instruction form may be tailored to the specific phonetic challenges faced by learners.