Introduction and Overview 1

Language aptitude and working memory in SLA

Even casual observations in our daily lives tell us that some people are able to learn a foreign or second language (L2) easier, faster and/or better than others (Grigorenko et al., 2000; Segalowitz, 1997). This common phenomenon is best captured by the concept of language aptitude in applied linguistics. By definition, L2 aptitude presupposes that 'there is a specific talent for learning foreign languages which exhibits considerable variation between individual learners' (Dörnyei & Skehan, 2003; Skehan, 1998). This underlying assumption of an L2 aptitude was put to considerable test as early as the 1950s and 1960s, mostly with respect to the research done by John Carroll on US military personnel (see Spolsky, 1995; Stansfield, 1989).

From the 1970s, however, research on L2 aptitude languished, with 'relatively little empirical work and little theorizing' taking place during the next three decades (Skehan, 2002: 69). This lack of research interest stemmed partly from several major criticisms levelled against the very concept of language aptitude per se (for more detailed discussion see Dörnyei & Skehan, 2003; Skehan, 1998, 2002). The first accusation was related to the anti-egalitarian 'labelling effect' of a concept that assigns the label of 'loser' to anyone who gets a low aptitude score (e.g. from the Modern Language Aptitude Test, or MLAT; Carroll & Sapon, 1959). The second accusation targeted the 'indecent origin' of the outdated teaching methodology used during the heyday of early language aptitude research (i.e. the audiolingual method, which was dominant in the 1950s when Carroll conducted most of his aptitude research). As a result of these accusations and other criticisms, such as Krashen's (1980) verdict that aptitude predicts only explicit learning, not language acquisition), there was little research on L2 aptitude from the 1970s until the 1990s (Wen et al., 2016).

In recent years, however, research on L2 aptitude has managed to gain some renewed momentum (Granena & Long, 2013; Granena et al., 2016; Li et al., 2015; Robinson, 2002). Intriguingly, this new body of research has consistently contradicted the criticisms made of the concept of language aptitude (Skehan, 2015b). For example, instead of being 'outdated' and 'ineffective', the concept of L2 aptitude is now being viewed as being very relevant to L2 learning, even in today's prevailing communicative L2 classrooms (Granena, 2013; Gregersen & MacIntyre, 2014; Skehan, 2015b; Vatz et al., 2013). More importantly, research on second language acquisition (SLA) has increasingly confirmed that L2 aptitude is not just confined to traditional instructional settings but is also relevant under different learning conditions (e.g. implicit versus explicit; Granena, 2015) and different learning contexts (Robinson, 2007). In a recent meta-analysis of the empirical research conducted over the past 50 years, Li (2015) provided compelling evidence of a positive link between L2 aptitude and L2 grammar learning.

Nonetheless, this renewed wave of research interest has been accompanied by concerted calls among researchers to reconsider and reconceptualize the construct of L2 aptitude (Ganschow & Sparks, 2001; Granena, 2013; Kormos, 2013; Parry & Child, 1990; Robinson, 2002b, 2005, 2012; Skehan, 1998, 2002, 2012, 2015b, 2016; Wen & Skehan, 2011). The current research on L2 aptitude is being actively pursued by scholars from multiple disciplines – educational psychology, applied linguistics, cognitive science and neuroscience (Wen, 2012b; Wen et al., 2016). Through these research efforts, a multitude of L2 aptitude models have been proposed, such as the linguistic coding difficulties hypothesis (LCDH) by Sparks and colleagues, the cognitive ability for novelty in the acquisition of language (CANAL-F) model by Grigorenko, Sternberg and colleagues, Peter Skehan's macro-SLA aptitude model and the 'aptitude complexes' model by Peter Robinson. Recently, cognitive scientists and neuroscientists have made significant contributions to L2 aptitude research by proposing innovative models from their own theoretical perspectives, including the impressive high-level aptitude battery (HiLAB) model and neurological and brain network-based aptitude models (Wen, 2012b; Wen et al., 2016).

Most relevantly, a consistent theme that has emerged either directly or indirectly from this renewed research interest is the proposal to incorporate the cognitive construct of working memory (WM) as a central component of L2 aptitude (e.g. Aguado, 2012; Hummel, 2009; Kormos, 2013; Linck & Weiss, 2015; McLaughlin, 1995; Miyake & Friedman, 1998; Sawyer & Ranta, 2001; Skehan, 1998, 2002, 2012; Wen, 2007, 2012b; Wen & Skehan, 2011; Williams, 2012, 2015; Yoshimura, 2001). This proposal has garnered increasing attention in recent years from SLA scholars interested in language aptitude research (e.g. Dekeyser & Koeth, 2011; Juffs & Harrington, 2011; Kormos, 2013; see also Ellis & Shintani, 2013; Mitchell et al., 2013; Singleton, 2014). This innovative conception of 'WM as L2 aptitude' thus constitutes the overarching theme of this book, and is fully discussed in Chapter 9. In other words, the first and foremost motivation of this book is to review and evaluate the extent to which the cognitive construct of WM plays a central role in SLA as an aptitude component.

L2 task-based planning and performance research in SLA

Situated within the postulation of 'WM as L2 aptitude', this book is also partially motivated by the ongoing debate in current research on L2 task-based language learning and teaching (Robinson, 2011; Skehan, 2011, 2014, 2015a, 2015c). In the realm of L2 task-based planning research, for example, an early paper by Rod Ellis (1987) is generally regarded as seminal in that it triggered enormous enthusiasm among SLA scholars to examine the variegated effects of planning on L2 task-based performance (R. Ellis, 2005; Skehan & Foster, 2012). These SLA scholars include Rod Ellis, Michael Long, Graham Crookes, Peter Skehan, Peter Robinson and Martin Bygate, among many others (Bygate, 2015). These scholars have published a number of empirical studies on this topic, culminating in an edited volume (R. Ellis, 2005) and a special issue of the journal Applied Linguistics, led by a review article by...