This study examined how individual differences in cognitive abilities account for variance in the attainment level of adult second language (L2) syntactic development. Participants completed assessments of declarative and procedural learning abilities. They subsequently learned an artificial L2 under implicit training conditions and received extended comprehension and production practice using the L2. Syntactic development was assessed at both early and late stages of acquisition. Results indicated positive relationships between declarative learning ability and syntactic development at early stages of acquisition and between procedural learning ability and development at later stages of acquisition. Individual differences in these memory abilities accounted for a large amount of variance at both stages of development. The findings are consistent with theoretical perspectives of L2 that posit different roles for these memory systems at different stages of development, and suggest that declarative and procedural memory learning abilities may predict L2 grammatical development, at least for implicitly trained learners.

The current study aims to make an initial neuroimaging contribution to central implicit-explicit issues in second language (L2) acquisition by considering how implicit and explicit contexts mediate the neural representation of L2. Focusing on implicit contexts, the study employs a longitudinal design to examine the neural representation of L2 syntax and also considers how the neural circuits underlying L2 syntax vary among learners who exhibit different levels of performance on linguistic and cognitive tasks. Results suggest that when exposed to a L2 under an implicit context, some learners are able to quickly rely on neural circuits associated with first language grammar and procedural memory, whereas other learners increasingly use extralinguistic neural circuits related to control mechanisms to process syntax. Thus, there may be multiple ways in which L2 is represented neurally, at least when learned under implicit contexts.

Extending previous research that has examined the relationship between long-term memory and second language (L2) development with a primary focus on accuracy in L2 outcomes, the current study explores the relationship between declarative and procedural memory and accuracy and automatization during L2 practice. Adult English native speakers had learned an artificial language over two weeks (Morgan-Short, Faretta-Stutenberg, Brill-Schuetz, Carpenter & Wong, 2014), producing four sessions of practice data that had not been analyzed previously. Mixed-effects models analyses revealed that declarative memory was positively related to accuracy during comprehension practice. No other relationships were evidenced for accuracy. For automatization, measured by the coefficient of variation (Segalowitz, 2010), the model revealed a positive relationship with procedural memory that became stronger over practice for learners with higher declarative memory but weaker for learners with lower declarative memory. These results provide further insight into the role that long-term memory plays during L2 development.

This study examined the role of procedural memory in adult second language (L2) development. Participants were trained on an artificial language under either explicit or implicit conditions. Development in the L2 was assessed by grammar tests at two time points. Measures of procedural memory were administered and were used to create high and low procedural groups. Results revealed an advantage in L2 development for learners with high procedural memory when trained in the implicit condition. Overall, this study suggests that procedural memory may be an important factor in adult L2 development but its role may differ under different learning contexts.

Statistical learning (SL) involving sensitivity to distributional regularities in the environment has been suggested to be an important factor in many aspects of cognition, including language. However, the degree to which statistically-learned information is retained over time is not well understood. To establish whether or not learners are able to preserve such regularities over time, we examined performance on an artificial second language learning task both immediately after training and also at a follow-up session 2 weeks later. Participants were exposed to an artificial language (Brocanto2), half of them receiving simplified training items in which only 20% of sequences contained complex structures, whereas the other half were exposed to a training set in which 80% of the items were composed of complex sequences. Overall, participants showed signs of learning at the first session and retention at the second, but the degree of learning was affected by the nature of the training they received. Participants exposed to the simplified input outperformed those in the more complex training condition. A GLMM was used to model the relationship between stimulus properties and participants’ endorsement strategies across both sessions. The results indicate that participants in the complex training condition relied more on an item’s chunk strength than those in the simple training condition. Taken together, this set of findings shows that statistically learned regularities are retained over the course of 2 weeks. The results also demonstrate that training on input featuring simple items leads to improved learning and retention of grammatical regularities.