Introduction

Variable outcomes in adult instructed language learning are widely accepted (Kiss, 2009), but child foreign language instructed learning is often assumed to be more homogeneous (Mihaljević Djigunović, 2009). Empirical evidence shows that this is unlikely to be the case, instead demonstrating considerable variation in young learner linguistic outcomes across a range of contextual factors; for example, nature of provision and teacher expertise (Murphy, 2014) and individual characteristics such as age (Johnstone, 2002; Muñoz, 2006), language learning strategies (Cameron, 2001), first language (L1) literacy skills (Sparks et al., 2009), socioeconomic status (Mattheoudakis & Alexiou, 2009) and aptitude in the form of memory and analytic skills (Alexiou, 2009). These kinds of differences create heterogeneous early FL learning classrooms which present a considerable challenge for teachers (Nikolov & Mihaljević Djigunović, 2011), especially as foreign language (FL) policy and practice is often grounded in certain assumptions about younger children learning languages: first, that younger children are better at learning languages due to brain plasticity conceptualised in the Critical Period Hypothesis (Lenneberg, 1967) and second that a younger start will increase exposure to linguistic input over a longer time span, resulting in enhanced linguistic outcomes.

Consequently, research that identifies and explores the implications of particular individual differences in young FL classrooms could be of interest to both policy-makers and practitioners. Working memory is an important individual difference in adult second language (L2) learning and has recently been linked to language learning aptitude (Wen, 2011). Evidence is emerging that verbal working memory (VWM), a sub-component of working memory, is important in both adult and child L2/FL learning. This mixed-methods study aims to contribute to the emerging evidence base reflecting individual differences in young FL learning by investigating the complex role of VWM in the development of FL general proficiency and FL literacy skills. Both quantitative and qualitative data in the form of FL test results and weekly written vocabulary work are presented and analysed in order to construct a nuanced portrayal of VWM as an individual difference in FL learning.