Although this special issue reveals some promising achievements, most of the contributions show that tasks of implicit learning are not or are only weakly correlated with each other, and they have inconsistent predictive power on L2 acquisition. This commentary examines four possible explanations for this surprising pattern: The (suboptimal) selection of tasks, the low reliability of measures, the deep influence of the starting level even for nominally “new” implicit tasks, and the fact that the mastery of L2 may involve other implicit processes than implicit learning measured through laboratory tasks.

This study examined the effect of choice on EFL learners’ task engagement. Twenty-four Thai university students completed two opinion-gap tasks. In one, they discussed and agreed on three items among given options (+constraint). In the other, they discussed and agreed on three items among the options they generated (−constraint). Spoken interaction and questionnaires were analyzed for behavioral (time on task, words produced, turns), cognitive (negotiation of meaning and form, self-repairs), social (overlaps and turn completion, backchannels), and emotional engagement (anxiety, enjoyment), based on Philp and Duchesne’s multifaceted model. The −constraint task had positive effects on all the cognitive engagement measures, but only one of the behavioral measures (turns) and one of the social measures (overlaps). Learners reported higher anxiety and enjoyment in the −constraint task. The findings highlight the interrelated multidimensional nature of learner task engagement while suggesting pedagogical implications and avenues for future research.

There has been limited research on the efficacy of captioned second language (L2) television in facilitating the incidental acquisition of multiword expressions (MWEs). The present study aims to fill this gap. Additionally, this study examines the role of typographic enhancement and repetition. One-hundred and twenty-two L2 learners were assigned to one of six conditions that differed in terms of caption condition (no captions, normal captions, enhanced captions) and the number of times they watched the same video (once, twice). The participants took a cued MWE form recall test before watching the video, immediately and 2 weeks after watching it. A content comprehension test was also administered. Compared to single viewing, repetition resulted in better content comprehension as well as better acquisition of MWEs. Both caption types positively influenced MWE recall relative to watching the video without captions, but typographic enhancement reduced the benefits of captions for content comprehension.

Listener-based ratings have become a prominent means of defining second language (L2) users’ global speaking ability. In most cases, local listeners are recruited to evaluate speech samples in person. However, in many teaching and research contexts, recruiting local listeners may not be possible or advisable. The goal of this study was to hone a reliable method of recruiting listeners to evaluate L2 speech samples online through Amazon Mechanical Turk (AMT) using a blocked rating design. Three groups of listeners were recruited: local laboratory raters and two AMT groups, one inclusive of the dialects to which L2 speakers had been exposed and another inclusive of a variety of dialects. Reliability was assessed using intraclass correlation coefficients, Rasch models, and mixed-effects models. Results indicate that online ratings can be highly reliable as long as appropriate quality control measures are adopted. The method and results can guide future work with online samples.

Two commonly used test types to assess vocabulary knowledge for the purpose of reading are size and levels tests. This article first reviews several frequently stated purposes of such tests (e.g., materials selection, tracking vocabulary growth) and provides a reasoned argument for the precision needed to serve such purposes. Then three sources of inaccuracy in existing tests are examined: the overestimation of lexical knowledge from guessing or use of test strategies under meaning-recognition item formats; the overestimation of vocabulary knowledge when receptive understanding of all word family members is assumed from a correct response to an item assessing knowledge of just one family member; and the limited precision that a small, random sample of target words has in representing the population of words from which it is drawn. The article concludes that existing tests lack the accuracy needed for many specified testing purposes and discusses possible improvements going forward.

This study combines explicit (pen-and-paper) and sensitive (time-pressured) measures to gauge the impact of three instructional interventions (contextualized input with meaning-focused activities, contextualized input with word-focused activities, and decontextualized input with word-focused exercises) on the learning of 20 L2 French target verbs. Participants (N = 313, L1 = Dutch) completed a combination of explicit (form recognition, meaning recall, grammatical preference) and time-pressured sensitive tests (lexical decision, semantic relatedness, grammaticality judgment) as immediate and delayed posttests. Explicit posttests show the beneficial effects of word-focused instruction, and underline the efficiency of context for meaning-related knowledge. Sensitive posttests generally confirm the explicit results, but reveal differences between both word-focused conditions related to lexical processing and strength of knowledge. This study suggests that combining explicit and sensitive measures can provide a more complete picture about the effects of L2 vocabulary instruction and shows that contextualized and decontextualized word-focused instruction benefit vocabulary learning in a complementary way.

In this commentary, we summarize the findings of the seven included studies that examined implicit language aptitude from various perspectives and highlight issues to be resolved in the validation of this new construct in second language research. We start by providing an overview of the contributions of the studies. We then identify the lack of convergent validity of the measures of implicit aptitude reported in the included studies and problematize the equally varied nature of the measurement of implicit knowledge—the outcome variable of aptitude research—and related concepts. In particular, by drawing on empirical evidence and theoretical claims, we attempt to clarify the relationships between implicit and explicit knowledge, implicit and explicit learning, and implicit and explicit instruction. Next, we draw attention to the interactions reported by the included studies between aptitude and outcome measures and between aptitude and instruction type, emphasizing the value and importance of interactional research. We conclude by making recommendations for future research.

Previous studies attest that early bilinguals can modify their perceptual identification according to the fine-grained phonetic detail of the language they believe they are hearing. Following Gonzales et al. (2019), we replicate the double phonemic boundary effect in late learners (LBs) using conceptual-based cueing. We administered a forced choice identification task to 169 native English adult learners of Spanish in two sessions. In both sessions, participants identified the same /b/-/p/ voicing continuum, but language context was cued conceptually using the instructions. The data were analyzed using Bayesian multilevel regression. Learners categorized the continuum in a similar manner when they believed they were hearing English. However, when they believed they were hearing Spanish, “voiceless” responses increased as a function of L2 proficiency. This research demonstrates the double phonemic boundary effect can be conceptually cued in LBs and supports accounts positing selective activation of independent perception grammars in L2 learning.

Monolingual English speakers and Chinese–English bilinguals were compared on their lexical decision performance in a masked priming experiment where the prime and target ended in the same embedded word. All primes were nonwords where the letters in addition to the embedded word did not form a morpheme (e.g., the sab of sabagree or the ple of plerough). The targets were of two types. In one condition they were prefixed words (as in sabagree–DISAGREE) and in the other they were nonprefixed words (as in plerough–THOROUGH). With an unrelated prime as the baseline, the native speakers showed priming for the prefixed words but not the nonprefixed words, whereas the nonnative speakers showed priming for both types of word. It was concluded from these results that nonnative speakers focus more on the individual letters of a complex word than do native speakers when reading, and the specific processing mechanisms that might underlie this are discussed.

Although retrieval of lexical forms is a prerequisite for language production, research of L2 vocabulary learning has focused much more on meanings and form-meaning mappings than on development of detailed, accessible mental representations of forms. This is particularly true with respect to multi-word items (MWIs). We report an experimental study involving a variety of intra-lexical, usage-based, and interlingual co-determinants of L2 vocabulary learnability pertaining to MWIs. Each learner (N = 60) encountered a randomly allocated set of 26 two-word MWIs (Nsets = 4) semi-randomly drawn from a larger pool of MWIs. Learners were asked to remember either the 13 MWIs showing the form variable assonance (e.g., change shape) or the 13 nonassonant control MWIs (e.g., sound good). Posttests of form recall revealed a large, durable effect of the focusing task in combination with forewarning of testing. Except when MWI concreteness (a semantic variable) was high, assonance had a positive effect on retrievability in recall tests given after delays of 15 minutes and one week. There was a consistent effect of the semi-semantic variable Mutual Information. Even in the context of a strong focus on forms, form variables are not the only variables that matter.

In the Afro-Colombian community of San Basilio de Palenque, there are school-based efforts to revitalize the once-endangered creole language Palenquero. At present, most Palenquero language classes do not include grammatical instruction, active student production, or corrective feedback, and there is little or no communication in Palenquero between L2 learners and fluent adult speakers. One result is that L2 Palenquero speakers are overgeneralizing the Palenquero prenominal plural marker to singular contexts, in a fashion that partly suggests a Spanish-influenced misinterpretation as a definite article. The present study summarizes oral and written production, and then analyzes processing data from an eye-tracking experiment confirming L2 learners’ emergent restructuring of the Palenquero plural marker. L2 learners have regularized perceived variation similar to learners of artificial languages, and the morphological marking of plurality is seemingly being lost, possibly morphing into an emergent but still unstable definiteness marker effectively delinked from number.

To probe the limits of attention raising through form-focused instruction, second-language research must adapt to the needs of a technologically driven learning environment. In this study, we used a randomized control design to investigate the effect of captioned media on the learning of vocabulary and grammar in L2 Spanish (n = 369 learners). Through four data-collection sessions, participants were presented with a grammar-lesson video and a multimodal video with one of three captioning formats: textually enhanced target vocabulary, textually enhanced target grammar, or no captioning. Results show strong immediate effects of captioning on target vocabulary, with additional effects of captioning on some, but not all, target-grammar structures. The findings demonstrate that (a) the learning of some grammatical structures is more conducive to captioning than others, and (b) there is space for future investigation into the factors that may influence the effectiveness of multimodal interventions, such as prior knowledge or frequency of use.