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Review of  Explaining differences in adult second language learning: The role of language input characteristics and learners' cognitive aptitudes

Reviewer: Alex K Magnuson
Book Title: Explaining differences in adult second language learning: The role of language input characteristics and learners' cognitive aptitudes
Book Author: Maja Ćurčić
Publisher: Netherlands Graduate School of Linguistics / Landelijke (LOT)
Linguistic Field(s): Language Acquisition
Issue Number: 30.566

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Maja Ćurčić’s (2018) dissertation provides an in-depth discussion, through three key experimental studies, of how the intersection between second language learners’ cognitive aptitudes and input characteristics mediate L2 learning. Thus, from the onset, the initial discussion addresses some of the concerns held by members of the Applied Linguistics community in trying to account for differing trajectories of adult second language development and posit ways to enhance language instruction. Despite the composition of the text including a variety of material from the domain of language aptitude and individual differences, it is not an introductory text nor a guide to designing empirical studies (albeit, the studies presented provide rich detail for design considerations). Instead, it is aimed to provide an in-depth look into an area that has more recently experienced a resurgence within the field (Dörnyei, 2005).


The first chapter, serving as an introduction to individual differences in the context of cognitive aptitudes, awareness, and input characteristics in L2 processing and second language acquisition, provides an overview of the theoretical and empirical motivating factors of the following studies that comprise the monograph. One of the central motivating factors for the first study is an extensive examination of “input reliability or consistency” which, according to Ćurčić, is lacking in L2 experimental research. Additionally, the problem space is limited early on and the focus is delineated as the interactions between cognitive aptitudes and input characteristics through two measures: grammaticality judgment tasks (GJTs) and an “unobtrusive measure,” the visual word eye-tracking paradigm (p. 2). For the studies, the target L2 structure involved noun/determiner agreement patterns derived from an artificial language. The chapter concludes with presenting the guiding research questions of the subsequent inquiries.

The second chapter aims to investigate input reliability, in terms of the features of input that impact pattern learning. Ćurčić immediately situates this study as an extension of usage-based approaches (see Bybee, 2008 for discussion) and those found in developmental psychology (see Saffran, Aslin, & Newport, 1996). The participants, 50 adult Dutch speakers, were exposed to auditory input from “a novel miniature language based on Fijian” (Ćurčić, 2018, p. 18) with a linguistic target of determiner-noun agreement. Two groups were formed: a reliable input group that heard only the target structure and an unreliable input group that was exposed to non-target structures. To measure aptitude, Ćurčić used the LLAMA D and F subtests from the freely available LLAMA battery of assessments (Meara, 2005), a serial reaction time task, and a non-verbal IQ test. To test the participants’ knowledge of the target structure, two oral grammaticality judgment tasks were utilized. The findings, derived from generalized linear models as the main statistical procedures, suggested that unreliable input generally impacts pattern learning negatively. Additionally, relations between memory capacity and the participants’ performances on the GJTs were found. However, as Ćurčić (2018) explains, “…we found no links between pattern learning and statistical learning ability…” which can be accounted for by the implicit nature of statistical learning and, in the author’s sample, “much of the learning was driven or accompanied by awareness” (p. 41). This is a critical distinction that is made as previous studies have indeed found relationships between the two. Finally, aptitude by treatment interactions (ATIs) revealed an interaction between input reliability and working memory, suggesting that benefits relating to working memory capacity can be limited by inhibitory factors (i.e., unreliable input).

The third chapter represents a partial replication and extension of the prior study described in the second chapter with the key factor being the use of prolonged exposure to the target structure (i.e., determiner-noun agreement). In this context, prolonged exposure is defined as 176 additional trials (484 total trials versus the original 308 trials), for an increase equating to approximately 60% (see p. 51 for discussion). While the results of the study replicated the previous findings that unreliable input could negatively affect participants’ learning when they were aware of the target pattern, it also provided evidence that “…unreliable input helped them to better memorize both regular items and exceptions” when unaware of the target and given prolonged exposure (p. 45). Ćurčić also contends that this replication should be carried out again, and if the results hold, then the implications for learning are of critical importance as “…exposure length and the moment at which learners’ knowledge is tested during the exposure may lead to substantial differences in what kind of performance is observed” (p. 71). Ćurčić’ maintains that this would lead to the identification of implicit learning only if conducted early enough in the learning stage.

In the fourth chapter, Ćurčić describes another related study focusing on the role of overt language input reversal in terms of its function with working memory and pattern learning. Once again, participants received auditory exposure to the novel miniature language with the determiner-noun agreement pattern as the target structure. To motivate this particular inquiry, Ćurčić acknowledges the established connection between learners’ working memory and linguistic pattern sensitivity, but cites Ellis and Sinclair (1996) as the only empirical study to have investigated the connection between grammar acquisition and rehearsal effects. To isolate rehearsal effects, the participants—also 50 native Dutch speakers—were grouped into one of two conditions: (a) a rehearsal group that performed an elicited imitation of the stimuli and (b) a group that heard the stimuli twice. To measure the participants’ knowledge of the target structure, two GJTs and a production task were used. The reported results indicated that pattern learning in general was only attributed to participants that became aware of the target structure. Moreover, some of these participants demonstrated gains while others did not. Ćurčić draws on usage-based theories posited by Abbot-Smith and Tomasello (2006) and Bybee (2008) to explain that this may be accounted for via the accumulation (or lack) of exemplar-based knowledge: in other words, some had enough and some did not. Interestingly, Ćurčić (2018) also claims that, based on the results, “…the benefits of rehearsal are due to learners’ vocal repetition of the input” thus demonstrating a facilitating effect (p. 103). Once again, a call for replication is made by Ćurčić for an investigation into rehearsal’s role in “context-based types of instruction” (p. 106).

The fifth chapter presents the final studies examined in the dissertation: an investigation of visual eye-tracking paradigm measures with differing levels of learner awareness, instruction type, and aptitude factors. Using the Fundamental Identity Hypothesis, Ćurčić guides the inquiry away from the differences between non-native and native processing and more so towards the individual differences that can account for different observations of online processing. Specifically, Ćurčić investigated the extent to which L2 processing of gender-marked determiners could be improved with both instruction and rehearsal through two studies employing the data collected from the previously discussed investigations in the other chapters (with a total of 100 participants for the first and 50 for the second study). Of focal interest for the first study is how awareness of the target structure, along with aptitudes, are potentially able to influence online L2 processing; the subsequent study is a replication of the first with an analysis of instruction type effects. Additionally, the inclusion of eye-tracking was used to determine if “…learners made rapid eye predictions about the coming noun based on the determiner they heard” (p. 119). The results suggested that “prediction aware learners” were the only ones to demonstrate predictive processing of the target determiners; moreover, gender awareness was necessary for such predictive processing to first occur (see p. 139 for discussion). The chapter concludes with a call for further investigation of these factors in tandem with other language structures.

The sixth and final chapter serves as a synthesized summary of the previous chapters and posits implications for the key tenants of the research: input reliability, pattern learning and aptitudes, L2 processing in the context of individual differences, and differences in learner awareness. After a discussion of the methodological considerations of using an artificial language and differing task types, Ćurčić briefly discusses potential, but limited, practical implications in the instructional context.


Overall, Ćurčić’s work is an ambitious and highly informative contribution to the field in terms of furthering our understanding of aptitude interactions, and by extension, how individual differences affect L2 input processing. The empirical studies detailed in this published dissertation are cogent and, despite their ability to stand as fully independent contributions, logically cohere into a more fully representative narrative of the roles of cognitive aptitudes and input characteristics within the domain of second language acquisition. Early on, Ćurčić addresses the lack of experimental research that attends to “…how input reliability affects learning of L2 patterns” (p. 4). To that goal, Ćurčić undoubtedly achieves this. As presented, the text can definitely serve as an engaging source of discussion and as a guide for a future research agenda for other researchers.

Despite these praiseworthy qualities, there are some areas which I felt, as a reader, could be revisited. While the introduction is undeniably helpful in setting the stage clearly for the reader to follow the ensuing chapter progression, an even more robust discussion of the relevant literature would have been desirable. Granted the scope of the chapter was intended to be limited, but the lack of a more thorough treatment somewhat inhibits the accessibility of the topic, especially for researchers with less familiarity with it and its subcomponents.

For example, while DeKeyser (2012) is mentioned, some of his more recent work along with Suzuki (2017) is largely absent. This omission is very noticeable, especially in the context of this study using some of the LLAMA battery subcomponents. Even more noticeable is the lack of a study that was designed to validate the LLAMA tests (see Rogers et al., 2017). This feels as if it is a missed opportunity, especially in Chapter 6.2 Aptitudes and pattern learning (pp. 145-149). While the use of the LLAMA tests was described, the motivations behind their use were not fully detailed. While the relative recency of these aforementioned articles may be partly to blame, these would undoubtedly enhance the discussions present in the text.

Another, yet minor critique, is the term “prolonged exposure” as defined in the third chapter. What constitutes prolonged exposure is not clearly situated within the existing literature. While it is operationalized as a 60% increase in trials, this does not appear to be theoretically motivated.

Finally, the practical implication section’s brevity is very noticeable. While Ćurčić readily admits that, “[b]ased on the results of this dissertation, it is difficult to see immediate implications for teaching,” (p. 155) and she does attempt to make modest connections, it leaves the reader yearning for more. However, this is admittedly not fully her responsibility as she has attempted to contribute to the current gaps in the field while presenting new areas for potential development by other researchers. This is most evident in her repeated—and most refreshing—invites for replication research of the presented studies.

While this text is a timely contribution to those already interested in aptitude and input, it is by no means an introductory primer. Thus, the audience for this volume may be more inherently limited in scope as it is more specialized. Irrespective of the daunting nature of the constructs presented, if one were to have an interest within these domains, then the actual presentation (i.e., the writing style and organization) is most reader-friendly and that does ameliorate some of the aforementioned accessibility issues. Despite some shortcomings, this text—as a whole—offers a fresh perspective on a promising area of continued research.


Abbot-Smith, K., & Tomasello, M. (2006). Exemplar-learning and schematization in a usage-based account of syntactic acquisition. The Linguistic Review, 23, 275-290.

Bybee, J. (2008). Usage-based grammar and second language acquisition. In P. Robinson, & N. Ellis (Eds.), Handbook of cognitive linguistics and second language acquisition (pp. 216-236). New York: Routledge.

Ćurčić, M. (2018). Explaining differences in adult second language learning: The role of language input characteristics and learners’ cognitive aptitudes (Published doctoral dissertation). The Netherlands: Netherlands Graduate School of Linguistics/Landelijke (LOT).

DeKeyser, R. M. (2012). Interactions between individual differences, treatments, and structures in SLA. Language Learning, 62, 189-200.

Dörnyei, Z. (2005). Language aptitude. In The psychology of the language learner: Individual differences in second language acquisition (pp. 31-64). Mahwah, NJ: Lawrence Erlbaum.

Ellis, N. C., & Sinclair, S. G. (1996). Working memory in the acquisition of vocabulary and syntax: Putting language in good order. The Quarterly Journal of Experimental Psychology Section A, 49(1), 234–250.

Meara, P. M. (2005). LLAMA language aptitude tests [Computer Software]. Swansea, UK: Lognostics. Available from

Rogers, V., Meara, P., Barnett-Legh, T., Curry, C., & Davie, E. (2017). Examining the LLAMA aptitude tests. Journal of the European Second Language Association, 1(1), 49-60.

Saffran, J. R., Aslin, R. N., & Newport, E. L. (1996). Statistical learning by 8-month-old infants. Science, 274(5294), 1926-1928.

Suzuki, Y., & DeKeyser, R. (2017). The interface of explicit and implicit knowledge in a second language: Insights from individual differences in cognitive aptitudes. Language Learning, 67(4), 747-790. doi:10.1111/lang.12241
Alex K. Magnuson is a Ph.D. candidate in Applied Linguistics at the Pennsylvania State University. In addition to teaching in the affiliated intensive English program, he also has experience in a variety of contexts including freshman and sophomore college composition for L1 and L2 writers, developmental English, and high school English (both in the U.S. and Japan). His current interests include SLA, assessment, and individual differences realized as language aptitudes.