Widespread use of the Modern Language Aptitude Test (MLAT) in L2 studies of individual differences implicitly assumes that L2 aptitude is a distinct cognitive facet. There is considerable evidence for prediction from L1 abilities to L2 learning. In this longitudinal study, L1-MLAT-L2 relations were examined in 307 US secondary students based on…

Millions of public-school students in the United States are identified as English language learners (ELLs), whose academic success is tied to their second language (L2) English education. Previous research in adult populations indicates that L2 proficiency is related to the contextual variable of the prevalence of one's first language (L1) among…

Purpose: This longitudinal study investigated the trajectory of Spanish article accuracy in Spanish-English dual language learners (DLLs) from preschool to first grade, addressing the need for longitudinal data on the variability of Spanish grammatical skills in DLLs in English immersion classrooms. Method: Language sample analysis was conducted…

Spanish-speaking students constitute the largest subgroup of emergent bilingual (EB) students in the United States. Using longitudinal data on a nationally representative sample of Spanish-English EBs, we explore profiles of English reading trajectories and how early individual differences (i.e., early Spanish reading and English oral proficiency)…

Research on the implementation of CLIL at the onset of primary school is limited and has largely overlooked the role of other sources of individual differences. This study investigated the effects of the CLIL approach to English learning, together with the effects of out-of-school exposure to the language through media and other sources of…

This paper examines evidence for relationships among individual differences (IDs) in L1 achievement, L2 aptitude, and L2 achievement. It begins by providing an overview of my academic journey from L1 educator to L2 researcher and explains the development of the Linguistic Coding Differences Hypothesis (LCDH). Next, I review Peter Skehan's…

This study, adopting a longitudinal approach, traces the dynamic word knowledge development of two essential dimensions (meaning and collocation) both receptively and productively in Chinese context. Seven freshmen students (from the same class in a university in Guangzhou) of different language levels were selected to be observed of their English…

In order to understand variability in second language (L2) acquisition, this study addressed how individual differences in cognitive abilities may contribute to development for learners in different contexts. Specifically, we report the results of two short-term longitudinal studies aimed at examining the role of cognitive abilities in accounting…

Comprehensive models of derived polymorphemic word recognition skill in developing readers, with an emphasis on children with reading difficulty (RD), have not been developed. The purpose of the present study was to model individual differences in polymorphemic word recognition ability at the item level among 5th-grade children (N = 173)…

The current study longitudinally examined the influence of aptitude on second language (L2) pronunciation development when 40 first-year Japanese university students engaged in practice activities inside and outside English-as-a-Foreign-Language classrooms over one academic year. Spontaneous speech samples were elicited at the beginning, middle,…

Adults demonstrate difficulty and pronounced variability when developing second language (L2) grammatical knowledge and reading skills. We examine explanations in terms of individual differences in working memory (WM). Despite numerous studies, the association between WM and adult second language (L2) acquisition remains unclear, and longitudinal…

This is the first collection of research studies to explore the potential for mixed methods to shed light on foreign or second language learning by young learners in instructed contexts. It brings together recent studies undertaken in Cameroon, China, Croatia, Ethiopia, France, Germany, Italy, Kenya, Mexico, Slovenia, Spain, Sweden, Tanzania and…

The main goal of this paper is to analyze how the age factor behaves as an alleged individual difference (ID) variable in SLA by focusing on the influence that the learning context exerts on the dynamics of age of onset (AO). The results of several long-term classroom studies on age effects will be presented, in which I have empirically analyzed…

The Foreign Language Classroom Anxiety Scale (FLCAS) has been challenged on the grounds that it may also assess language learning skills. In this study, 128 students who had been administered measures of first language (L1) skills in elementary school were followed from 1st to 10th grade. Fifty-three students had completed second language (L2)…

In this article, I describe studies conducted over 25 years with secondary and post-secondary L2 learners in the United States. The evidence from these studies shows that there are important connections between students' early L1 skills and their L2 aptitude and L2 proficiency and that individual differences in students' L1 skills in elementary…