Are certain types of instruction better for certain learners? Pavel Trofimovich * , Patsy M. Lightbown, Randall Halter Centre for the Study of Learning and Performance, Concordia University, Montre´al, Canada Received 25 September 2011; revised 11 September 2013; accepted 13 September 2013 Available online 16 October 2013 Abstract The goal of this study was to investigate a possible link between second language (L2) learners’ background variables and the type of instruction learners receive in L2 classrooms. We specifically focused on the relationship between several learner back- ground factors (e.g., L2 contact, native language literacy skills, general academic ability) and measures of L2 speaking by analyzing the data from a large-scale longitudinal project investigating two different methods of teaching English as an L2 (comprehension- based vs. “traditional” L2 program). We found that the learners who had greater contact with English, who showed more interest in reading, whose parents spoke more English, and who attained higher scores in French reading, English vocabulary recognition and general school ability tended to produce more accurate and comprehensible English sentences in an elicited imitation task. However, this relationship was stronger in the comprehension-based than in the traditional program, revealing a possible interaction between type of instruction and learner background variables. Taken together, these findings suggest that certain types of instruction could be more beneficial for learners with certain learning profiles and highlight the importance of investigating interactions be- tween learner background variables and type of instruction in authentic learning contexts. Ó 2013 Elsevier Ltd. All rights reserved. Keywords: Aptitude-treatment interaction; Learner background; Aptitude; Classroom instruction; Second language speaking; Comprehensibility 1. Introduction The idea that certain types of instruction may be of greater or lesser benefit for learners with different background profiles is not new. A great deal of educational research in the 1970s and 1980s was devoted to the topic of aptitude- treatment interaction (ATI), which explores differences in effectiveness of instruction for learners with various background profiles (for reviews, see Snow et al., 1980; Vatz et al., 2013). At the heart of this research was the idea that an individual’s aptitude, defined as “any measurable person characteristic hypothesized to be [required for] successful goal achievement in the treatment(s) studied”, may determine this individual’s learning outcomes after a particular treatment (Snow, 1991, p. 205). In this sense, the term aptitude is to be understood more broadly than simply in- telligence or cognitive capacities underlying learning. Instead, it encompasses a variety of cognitive, personality, experiential, motivational, and social variables, including memory, musical ability, attitudes, motivation, beliefs and many others (Snow, 1991, 1994; Snow and Lohman, 1984). * Corresponding author. Concordia University, Department of Education, 1455 de Maisonneuve Blvd. West, Montre ´al, Que ´bec, Canada H3G 1M8. Tel.: þ1 514 848 2424x2448; fax: þ1 514 848 4520. E-mail address: pavel.trofimovich@concordia.ca (P. Trofimovich). 0346-251X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.system.2013.09.004 Available online at www.sciencedirect.com ScienceDirect System 41 (2013) 914e922 www.elsevier.com/locate/system