As part of ongoing efforts to characterize the extent to which tasks and interaction-driven language learning are influenced by individual differences (IDs), task-based researchers have thus far examined variables like learners’ levels of L2 anxiety, motivation, cognitive creativity, working memory capacity, and aptitude. Building on a tradition of prior syntheses in task-based language teaching (TBLT, e.g., Plonsky & Kim, 2016), we carried out a methodological review of the practices used by researchers who have examined learners’ IDs in task-based language learning. We searched journal articles published between 2000 and 2023 and identified 135 unique samples for analysis. Each empirical study was coded for relevant contextual and demographic variables as well as for methodological features related to the investigation of individual differences. We observed that of 30 individual differences investigated in TBLT research over the last two decades, the top five most common were motivation, working memory, L2 proficiency, anxiety, and aptitude. Interesting patterns related to operationalizations, instruments, coding, analyses, and reporting practices. In this paper, we report these results and summarize the most and least common methodological practices, also pointing out gaps and possibilities for future directions. We conclude with recommendations for researchers interested in embarking on empirical investigations of individual differences and TBLT based on best practices.

Concerns have recently been raised about the validity of scales used in the L2 motivational self system tradition, particularly in relation to sufficient discriminant validity among some of its scales. These concerns highlight the need to systematically examine the validity of scales used in this tradition. In this study, we therefore compiled a list of 18 scales in widespread use and administered them to Korean learners of English (N = 384). Testing the factorial structure of these scales using multiple exploratory and confirmatory factor-analytic criteria revealed severe discriminant validity issues. For example, the ideal L2 self was not discriminant from linguistic self-confidence, suggesting that participant responses to such ideal L2 self items is not driven by actual–ideal discrepancies as previously presumed but more likely by self-efficacy beliefs. We discuss these results in the context of the need to encourage systematic psychometric validation research in the language motivation field.

The use of connectives has been considered important for assessing the cohesion of written texts (Crossley et al., 2019). However, existing connective-based indices have not systematically addressed two issues of ambiguity, namely, that between discourse and non-discourse use of polysemous word forms and that in terms of the specific discourse relations marked by polysemous discourse connectives (Pitler & Nenkova, 2009). This study proposes 34 sense-aware connective-based indices of cohesion that account for these issues and assesses their predictive power for cohesion ratings in comparison to 25 existing indices. Results from the analysis of 3,911 argumentative essays from the English Language Learner Insight, Proficiency and Skills Evaluation Corpus show that 23 sense-aware indices but only three existing indices correlated significantly and meaningfully with cohesion ratings. The sense-aware indices also exhibited greater predictive power for cohesion ratings than existing indices. The implications of our findings for future cohesion research are discussed.

This study investigates the effects of retrieval schedules on the acquisition of second language (L2) collocations. Chinese learners of English first studied 36 target verb-noun collocations using flashcards and form-meaning matching practice. Subsequently, the participants practiced retrieving the target collocations from memory, following either a massed (consecutive) or spaced schedule. After each retrieval attempt, corrective feedback was provided. The acquisition of L2 collocations was measured by near-immediate and 1-week delayed posttests that assessed explicit knowledge with an offline form recall task, automatized explicit knowledge using an online acceptability judgment task, and implicit knowledge with an online collocation priming (lexical decision) task. Results showed equal learning effects of massed and spaced retrieval at both posttests of explicit knowledge and the near-immediate posttest of automatized explicit knowledge. The spacing effect was observed for the implicit knowledge across the two posttests and the automatized explicit knowledge at the delayed posttest.

This study investigates the extent to which (a) Spanish heritage (HL) and second language (L2) writers’ linguistic complexity differs across register contexts and (b) Spanish proficiency and writing motivational beliefs differentially affect HL and L2 writers’ performance. Participants were 58 HL and 54 L2 Spanish learners who completed two persuasive writing tasks—the Email to Friend and Letter to Dean tasks—designed to be topically similar while eliciting different registers. Proficiency measures included an elicited imitation task (EIT) and a cloze test. Mixed-effects models indicated that both HL and L2 writers evidenced greater lexico-syntactic complexity in the Letter to Dean task; nonetheless, HL writers demonstrated more robust cross-register distinctions in syntactic complexity. The EIT and cloze test positively predicted syntactic and lexical complexity, respectively, although differential patterns were also observed by group. Intrinsic/interest and cognitive/linguistic value beliefs about Spanish writing emerged as positive and negative predictors of linguistic complexity, respectively.

The current study set out to examine to what degree age of acquisition (AOA), defined as a learner’s first intensive exposure to a second language (L2) environment, mediates the final state of postpubertal, spoken vocabulary attainment. In Study 1, spontaneous speech samples were elicited from experienced Japanese users of English (n = 41) using storytelling and interview tasks. The samples were analyzed using a range of corpus- and rater-based lexical measures and compared to the speech of inexperienced Japanese speakers (n = 40) and native speakers of English (n = 10). The results showed that most experienced L2 learners tended to demonstrate nativelike proficiency for relatively easy lexical dimensions of speech (i.e., richness), but that AOA appeared to play a key role in predicting the ultimate attainment of relatively difficult lexical dimensions (i.e., appropriateness). In Study 2, the findings were successfully replicated with experienced L1 Polish users of English (n = 50).

To test the contributions of processing to L2 syntax learning, this study explores (cross-) linguistic and cognitive predictors of sentence reanalysis in the L2 comprehension of relative clauses among low-intermediate L1 German adolescent learners of L2 English. Specifically, we test the degree to which L2 comprehension is affected by L2 proficiency, reanalysis ability in a related, earlier-acquired L2 structure (questions), reanalysis ability of relative clauses in the L1, cognitive control, and cognitive capacity. In visual-world eye-tracking experiments, 141 adolescent German-speaking L2 learners of English selected target pictures for auditorily presented questions and relative clauses in the L1 and in the L2. The results showed a strong subject preference for L2 relative clauses. Learners’ L2 proficiency and their processing of object questions in the L2 predicted reanalysis for object relatives in eye movements, reaction times, and comprehension accuracy. In contrast, there was no evidence that cognitive control or working memory systematically affected the processing of object relatives. These findings suggest that linguistic processing outweighs cognitive processing in accounting for individual differences in low-intermediate L2 acquisition of complex grammar. Specifically, learners recruit shared processing mechanisms and routines across grammatical structures to pave a way in the acquisition of syntax.

Since Gisela Granena’s influential work, LLAMA D v2, a sound recognition subtest of LLAMA aptitude tests, has been used as a measure of implicit learning aptitude in second language acquisition research. The validity of this test, however, is little known and the results of studies with this instrument have been somewhat inconsistent. In this study, we tested the hypothesis that researchers’ variable test instructions are the source of the inconsistent results. One hundred fourteen English monolinguals were randomly assigned to take LLAMA D v2 under one of three test instruction conditions. They also completed two implicit aptitude tests, three explicit aptitude tests, and a sound discrimination test. The results showed that, regardless of the type of test instructions, LLAMA D scores did not align with implicit aptitude test scores, indicating no clear evidence of the test being implicit. On the contrary, LLAMA D scores were negatively associated with scores on one implicit aptitude test, the Serial Reaction Time (SRT) task, but only in the condition where the instructions drew participants’ focal attention to the stimuli. This negative association was interpreted as focal attention working against learning in the SRT task. Implicit learning aptitude may be the degree to which one is able to process input without focal attention.

We present a learner corpus-based study of English article use (“a”/“the”/Ø) by L2 learners with four typologically distinct first languages (L1s): German and Brazilian Portuguese (both have articles), Chinese and Russian (no articles). We investigate several semantic and morphosyntactic factors—for example, specificity, prenominal modification that can affect article use. Our analysis of 660 written scripts from the Education First Cambridge Open Database confirms the lower overall accuracy of learners with no-article L1s. Our main finding is the differential effect of specificity on definite and indefinite articles: learners tend to associate specificity with “a,” which implies article omission with nonspecific indefinite singulars and overuse of “a” with specific indefinite mass nouns. Prenominal modifiers further contribute to perceived specificity, leading to article overuse with modified indefinite mass nouns. However, in definite contexts, prenominal modifiers are associated with increased article omission.

Usage-based theories hold that mental representation of language is shaped by a lifetime of usage. Both input to which first language (L1) and second language (L2) users are exposed and their own language production affect their construction learning and entrenchment. The present study investigates L2 users’ knowledge of two introductory-it variants, Adj-that (e.g., it is clear that …) and Adj-to (e.g., it is difficult to …). We probed the extent to which adjective–variant associations in an academic section of COCA and L2 users’ engagement with academic writing affected learners’ generation of adjectives distinctively attracted to the two variants. An analysis of cue-outcome contingency was conducted to establish adjective–variant associations, and an elicitation task was carried out, probing L2 users’ ability to generate adjectives when prompted with the variants (e.g., it is [blank] to). The participants were 84 graduate students in the United States, 44 from L1 English and 40 from L1 Thai backgrounds. The results indicated that the adjective–variant associations predicted L2 users’ generation of adjectives. However, academic writing engagement did not affect learners’ performance. The findings suggest that statistical information in the input affects L2 users’ constructional representation.

Personality has been identified as a possible antecedent to emotions experienced in the foreign language (FL) classroom. However, contrasting results and differing personality models have resulted in ambiguous findings. This study set out to delve deeper into the role of personality as a predictor of FL emotions through a series of increasingly restrictive statistical models on a sample of n = 246 FL learners. The relationships between personality—operationalized as global and lower order factors in the five factor model—and the FL emotions of Foreign Language Enjoyment, Anxiety, and Boredom were examined. The global factors of Neuroticism, Extraversion, and Conscientiousness, and the lower order factors of Trust, Dutifulness, and Cheerfulness were significant predictors of FL emotions. However, the complexity of personality as a predictor variable is demonstrated in the intricacy of the results and as such the inclusion of personality in explanatory models of FL emotions ought to be approached with caution.

The congruency effect—that is, faster and more accurate processing of congruent multiword units, has been demonstrated in multiple studies. It is still unclear, however, what its underlying mechanism is, and how congruency may interact with other factors. Using an acceptability judgement task, this study examined the congruency effect in immersive (Experiment 1) and nonimmersive (Experiment 2) L2 learners’ collocational processing while taking into account L2 collocation frequency, immersive learners’ L2 use, their length and starting age of immersion, nonimmersive learners’ length of instruction, and their L2 proficiency. The study also tested whether L1 counterparts of words in L2 collocations were activated. Nonmmersive learners showed a congruency effect in both processing speed and accuracy. In contrast, immersive learners were affected by congruency only in processing accuracy. Higher L2 collocation frequency, greater length of instruction, and higher L2 proficiency did not reduce the congruency effect, whereas longer duration of immersion improved the processing of incongruent items. An effect of L1 lexical frequency was found, an indication of L1 activation. Results were discussed in light of how L2 proficiency and experiences changed the amount of L1 influence in L2 collocational processing.

The present study uses self-paced reading as a measure of online processing and an acceptability judgement task as a measure of offline explicit linguistic knowledge, to understand L2 learners’ comprehension processes and their awareness of subtle differences between the modal auxiliaries may and can. Participants were two groups of university students: 42 native speakers of English and 41 native speakers of Croatian majoring in L2 English. The study is part of a larger project that has provided empirical evidence of the two modals, may and can, being mutually exclusive when denoting ability (can) and epistemic possibility (may) but equally acceptable in pragmatic choices expressing permission. The present results revealed that L1 and L2 speakers rated the acceptability of sentences in offline tasks similarly; however, L2 learners showed no sensitivity to verb–context mismatches in epistemic modality while demonstrating sensitivity when processing modals expressing ability. Implications for L2 acquisition of modals and future research are discussed.

Second language (L2) research on input manipulation has focused mainly on increasing the salience of target structures, but presentation formats of L2 input can be another important aspect for manipulation. This study compared the horizontal, vertical, and adjacent formats for presenting the characters, pinyin, and English meaning of L2 Chinese vocabulary, by recruiting 69 English native speakers to study 30 Chinese words in these formats. Learning outcomes were indexed with vocabulary gain scores from pretest to posttest. Learner perceptions of the learning process were recorded with ratings and reasons for preference among these formats. The quantitative results showed the adjacent format generally led to higher gain scores than the other two formats and that L2 proficiency also contributed positively. To learners, the adjacent format was the least preferred, but preference ratings were not associated with gain scores. The qualitative findings suggested format familiarity and layout features as main factors of learner preference.

Usage-based theory has proposed that learning of linguistic constructions is facilitated by input that contains few high-frequency exemplars, in what is known as a skewed (or Zipfian) input distribution. Early empirical work provided support to this idea, but subsequent L2 research has provided mixed findings. However, previous approaches have not explored the impact that cognitive traits (e.g., working memory) have on the effectiveness of skewed or balanced input. The experiment reported here tested learners’ ability to develop new L2 categories of adjectives that guide lexical selection in Spanish verbs of “becoming.” The results showed that, when explicit rules are provided, low-working memory learners benefitted from reduced variability in skewed input, while high-working memory individuals benefitted from balanced input, which better allows for rule-based hypothesis testing. The findings help clarify the mixed findings in previous studies and suggest a way forward for optimizing the L2 input based on individual traits.