Cognitive scientists across disciplines have shown a vested interest in examining if and how the speech perception and production modalities are connected. The field of second language (L2) acquisition contributes to this discussion by investigating the effects of auditory training of L2 sounds on pronunciation. This meta-analysis offers a comprehensive view of the last 25 years of L2 perception training studies that test for effects in production. The results indicate that the two modalities are connected, insomuch as training the perception of L2 sounds can induce positive change in the productive mode as well. The data indicate that strictly controlled perception training led to medium-sized improvements in perception (d = 0.92, SD = 0.96) and small improvements in production (d = 0.54, SD = 0.45). A correlation analysis suggests a small- to medium-sized relationship between perception and production gains, although this relationship was not significant. The production of obstruents improved to a larger degree than sonorants or vowels, and an additional six moderating variables influenced the magnitude of the production effect sizes. We caution researchers to not equate the connection of the two modalities in long-term linguistic development to real-time neurological processing, and we end with five recommendations for the domain of L2 phonetic training research.

Spanish [l] is characterized as clear, and is associated with a high second formant (F2) frequency and a large difference between F2 and the first formant (F1) frequencies. In contrast, English [l] is darker (with a lower F2 and a relatively smaller F2–F1 difference) and also exhibits contextual variation due to an allophonic velarization rule that further darkens [l] postvocalically. We aimed to determine if Spanish–English bilingual children evidence these differences productively, in a manner comparable to that of monolinguals, or if they produce an [l] that is intermediate to that of Spanish and English monolinguals. We acoustically analyzed [l] productions of seven Spanish–English bilingual, seven Spanish monolingual, and seven English monolingual children. Results showed that the bilinguals had similar prevocalic F2 and F2–F1 values for [l] in both languages, comparable to those of Spanish monolinguals, but significantly higher than those of English monolinguals. The bilinguals also produced English (but not Spanish) [l] with significantly lower postvocalic F2 and F2–F1 values. We assume that the bilinguals have a merged phonetic category for prevocalic [l] but not postvocalic [l], and further, that they maintain separate grammars, allowing the allophonic velarization rule to apply in English but not Spanish.