Evidence for the role of procedural memory in second language (L2) acquisition has emerged in our field. However, little is known about the reliability and validity of the procedural memory measures used in this research. The present study (N = 119) examined the reliability and the convergent and discriminant validity of three assessments that have previously been used to examine procedural memory learning ability in L2 acquisition, the dual-task Weather Prediction Task (DT-WPT), the Alternating Serial Reaction Time Task (ASRT), and the Tower of London (TOL). Measures of declarative memory learning ability were also collected. For reliability, the DT-WPT and TOL tasks met acceptable standards. For validity, an exploratory factor analysis did not provide evidence for convergent validity, but the ASRT and the TOL showed reasonable discriminant validity with declarative memory measures. We argue that the ASRT may provide the purest engagement of procedural memory learning ability, although more reliable dependent measures for this task should be considered. The Serial Reaction Time task also appears promising, although we recommend further consideration of this task as the present analyses were post hoc and based on a smaller sample. We discuss these results regarding the assessment of procedural memory learning ability as well as implications for implicit language aptitude.

We would like to thank Robert DeKeyser for comments on an earlier version of this chapter, as well as attendees of the 2017 International Round Table Forum on Language Aptitude at the Macao Polytechnic Institute. We also thank members of the Cognition of Second Language Acquisition Laboratory at the University of Illinois at Chicago for helpful comments.

Evidence for the role of procedural memory in second language (L2) acquisition has emerged in our field. However, little is known about the reliability and validity of the procedural memory measures used in this research. The present study (N = 99) examined the reliability and the convergent and discriminant validity of three assessments that have previously been used to examine procedural memory learning ability in L2 acquisition, the dual-task Weather Prediction Task (DT-WPT), the Alternating Serial Reaction Time Task (ASRT), and the Tower of London (TOL). Measures of declarative memory learning ability were also collected. For reliability, the DT-WPT and TOL tasks met acceptable standards. For validity, an exploratory factor analysis did not provide evidence for convergent validity, but the ASRT and the TOL showed reasonable discriminant validity with declarative memory measures. We argue that the ASRT may provide the purest engagement of procedural memory learning ability, although more reliable dependent measures for this task should be considered. The Serial Reaction Time task also appears promising, although we recommend further consideration of this task as the present analyses were post hoc and based on a smaller sample. We discuss these results in regard to the assessment of procedural memory learning ability as well as implications for implicit learning aptitude.

Domain-general approaches to second language acquisition (SLA) have considered how individual differences in cognitive abilities contribute to foreign language aptitude. Here, we specifically consider the role of two, long-term, cognitive memory systems, i.e., declarative and procedural memory, as individual differences in SLA. In doing so, we define and review evidence for the long-term declarative and procedural memory systems, consider theories that address a role for declarative and procedural memory in L2 acquisition, discuss evidence in support of the claims that these theories make, and conclude with discussion of important directions and questions for future research on the role of declarative and procedural memory as individual differences in assessing L2 aptitude. DECLARATIVE AND PROCEDURAL MEMORY IN L2 APTITUDE 1 Declarative and Procedural Memory as Individual Differences in Second Language AptitudeResearch in second language (L2) aptitude addresses the components that together constitute aptitude, where aptitude is regarded as a latent construct or trait that predicts outcomes in L2 acquisition (Wen, Biedroń, & Skehan, 2017). Recent approaches to L2 aptitude have considered aptitude to be comprised of cognitive abilities (Ellis, this volume;Wen et al., 2017), including constructs such as attentional control and working memory (Robinson, 2007;Skehan, 2016; Wen, this volume). Thus, individual differences in these cognitive abilities would assumedly contribute to differing levels of L2 aptitude among individuals. An emerging line of research suggests that long-term memory may also serve as an individual difference factor in L2 learning. More specifically, declarative and procedural memory, both of which are domaingeneral, cognitive, long-term memory systems have been posited to play a role in L2 learning (DeKeyser, 2015;Paradis, 2009;Ullman, 2015), and individual difference research largely supports these claims (e.g., Antoniou, Ettlinger, & Wong, 2016; Faretta-Stutenberg & MorganShort, 2017;Hamrick, 2015;Morgan-Short, Faretta-Stutenberg, Brill-Schuetz, Carpenter, & Wong, 2014).The current chapter considers the role of declarative and procedural memory in L2. First, we provide detailed definitions of declarative and procedural memory and knowledge, and then review three theoretical perspectives that posit that declarative and procedural memory contribute to L2 acquisition: Ullman (2015), Paradis (2009), and DeKeyser's Skill Acquisition Theory (DeKeyser, 2015). Subsequently, we provide a review of empirical evidence that examines whether declarative and procedural memory can account for individual differences in L2 learning, as would be predicted by the theoretical perspectives. Finally, we provide a discussion of future research directions in regard to the role of declarative and procedural DECLARATIVE AND PROCEDURAL MEMORY IN L2 APTITUDE 2 memory in L2 and conclude that these long-term memory constructs should potentially be considered as components of L2 aptitude. Long-term Memory Systems Decl...