Cunnings’ keynote article outlines a novel approach to native/non-native differences in on-line language comprehension by proposing that L2 speakers are more susceptible to cue-based retrieval interference than natives. Cue-based, parallel access approaches to processing have been prominent in monolingual studies for around 15 years now, but have barely been applied to L2/bilingual processing. We are particularly excited about the possibilities that this approach offers for understanding L1, L2 and bilingual processing, as well as individual differences. In this commentary, we focus on two issues: 1) whether the existing evidence for cue-based retrial mechanisms in L2 processing support a deficit model, as Cunnings seems to claim, and 2) how individual differences may explain both similarities and differences in L1 and L2 processing.

Bilingual speakers are less accurate and slower than monolinguals in word production. This bilingual cost has been demonstrated primarily for nouns. This study compared verb and noun retrieval to better understand bilingual lexical representation and test alternate hypotheses about bilingual cost. Picture naming speeds from highly proficient English–Spanish bilinguals showed a smaller bilingual cost for verbs compared to nouns. In Experiment 1, picture naming speeds were influenced by name agreement, age-of-acquisition and word length. Additionally, noun (but not verb) naming speed was predicted by word frequency. Experiment 2 examined two potential explanations for the smaller bilingual cost for verbs: verbs experience weaker cross-language interference (measured by translation speed) and smaller frequency effects. Both these predictions were confirmed, showing crucial differences between verbs and nouns and suggesting that cross-language facilitation rather than interference influences bilingual lexical retrieval, and that the frequency lag account of bilingual cost is more applicable to nouns than to verbs. We propose a Bilingual Integrated Grammatical Category model for highly proficient bilinguals to represent lexical category differences.

Code-switching, switching between different languages within the same conversation, is a prominent feature in bilingual communication. This study aimed to elucidate to what extent the linguistic abilities and age of dual-language-learning preschoolers influence the frequency and purposes of code-switching (compensatory, to bridge linguistic gaps; preferential, to express content as fluently as possible; pragmatic, to phrase something appropriately for the situation). Parental code-switching ratings of 101 German/French–Turkish/Italian dual-language learners aged 32–78 months were analyzed. Generalized linear mixed models revealed positive but no negative effects of societal- and heritage-language skills on children's code-switching frequencies independent of switching purposes and with no evidence of age effects. Hence, code-switching across the preschool age mainly reflects high linguistic competences. Models with linguistically and psychometrically parallelized language scores indicated a strong switching tendency toward the societal language when proficiency in both languages is high, and away from the societal language when language proficiencies are low.

In this two-part study, we conducted both cross-sectional and longitudinal investigations on the relative weights of experiential, cognitive, and sociopsychological factors in adult L2 speech learning. In the cross-sectional phase (Study 1), speech was elicited from 73 Japanese speakers of English via a picture description task, and rated for accentedness and comprehensibility. These scores were linked to scores on a range of tests designed to measure aptitude, motivation, and anxiety. The results showed that comprehensibility was exclusively linked to experiential variables (e.g., the amount of L2 use outside classrooms), while accentedness was linked to phonemic coding ability and anxiety. In the longitudinal phase (Study 2), we tracked the same participants' L2 comprehensibility and accentedness development when they received four weeks of explicit pronunciation instruction. According to the results of pre- and post-tests, participants significantly improved the comprehensibility and accentedness of their speech regardless of cognitive and sociopsychological differences.

Recent evidence demonstrates that lexical-semantic connections emerge over the second year of life for monolingual children. Yet, little is known about the developing lexical-semantic organization of children acquiring two languages simultaneously. Two- to 4 year-old French–Spanish bilingual children completed a within-language auditory semantic priming task in both of their languages, while event-related potentials (ERPs) were recorded. The results revealed that bilingual children exhibited sensitivity to taxonomic relationships between words in each of their languages, but the pattern of brain activity varied across the dominant (DL) and the non-dominant (NDL) languages. While the N2 occurred for both languages, the N400 appeared for target words in the DL only and the late anterior negativity for target words in the NDL only. These findings indicate that words are organized taxonomically in the bilinguals’ lexicons. However, the patterns of brain activity suggest that common and distinct neural resources underlie lexical-semantic processing in each language.

In a between-language lexical priming study, we examined to what extent the two languages in a simultaneous bilingual child's lexicon interact, while taking individual differences in language exposure into account. Primary-school-aged Dutch–Greek bilinguals performed a primed picture selection task combined with eye-tracking. They matched pictures to auditorily presented Dutch target words preceded by Greek prime words. Their reaction times and eye movements were recorded. We tested for effects of between-language phonological priming, translation priming, and phonological priming through translation. Priming effects emerged in reaction times and eye movements in all three conditions, at different stages of processing, and unaffected by language exposure. These results extend previous findings for bilingual toddlers and bilingual adults. Processing similarities between these populations indicate that, across different stages of development, bilinguals have an integrated lexicon that is accessed in a language-nonselective way and is susceptible to interactions within and between different types of lexical representation.

Dijkstra, Wahl, Buytenhuijs, van Halem, Al-jibouri, de Korte, and Rekké (2018) present in their keynote article a promising computational model of word recognition and word production in monolinguals and bilinguals, called Multilink. We agree with the authors that the model is a “basis for the development of a more general computational model of word retrieval” (Dijkstra et al., 2018). However, it is also important that such a model is universal.

This special issue began as a conference on Bilingual and Multilingual Interaction at Bangor University in 2012. The papers collected here all have novel elements, either because of their innovative methods, their unusual data, or their unexpected findings. They present findings from studies of bilinguals speaking six different pairs of languages, and use a range of methods including experiments, naturalistic observation and auditory judgment data. Despite the differences in subject matter and methodological approaches, all the papers demonstrate that bilinguals draw on resources which are different from those of monolinguals. They show that the two languages spoken by bilinguals have clearly discernible effects on one another, and that these effects can potentially be enhancing. Future research will no doubt build on the studies presented here and extend our understanding of cross-language effects in bilingual production and comprehension.

The contribution that Ton Dijkstra has made to the field of bilingualism, with his colleagues over the years, is beyond measure. He has advanced our field with the thoughtful and thought-provoking models of the bilingual lexicon he has put forward, and with the vast empirical data he and his colleagues have collected from numerous bilinguals, using a variety of experimental methods. This paper by Dijkstra, Wahl, Buytenhuijs, van Halem, Al-jibouri, de Korte, and Rekké (2018) is no exception. It comprises a thoughtful and detailed description of a new model, Multilink, and provides relevant information regarding the context in which the model was developed, its assumptions, its successes and challenges. The model is the first to consider aspects of both word production and word recognition, as well as of word translation, and to explicitly address how translation equivalents that share both form and meaning – cognates – may be processed. Also addressed are word-frequency concerns, including differences in word frequency that are dependent on language proficiency and exposure. The assumptions that are made within the model are clearly laid out, and less-than-ideal decisions that needed to be made are acknowledged. The authors conclude that a model like Multilink could be the basis for a general model of the mental lexicon. In that, they promote the view taken in Libben, Goral, and Libben (2017) that the bilingual – not the monolingual – lexicon should be considered as the default.

The issue of critical or sensitive periods affecting the outcome of second language (L2) acquisition has been the subject of intense investigation and debate for many years, with people arguing for or against maturational effects on ultimate attainment. In their influential paper, Johnson and Newport (1989) identify two hypotheses: the exercise hypothesis and the maturational state hypothesis. According to the former, if the capacity for acquiring language is exercised early in life (in first language acquisition), then language learning abilities will remain intact throughout life: in other words, permitting successful L2 acquisition regardless of age. In contrast, according to the maturational state hypothesis, the language learning capacity declines with age, affecting L2 acquisition as well as late L1. Johnson and Newport take their results, which show an age-related decline in performance during childhood and adolescence, to support the maturational state hypothesis. Many L2 researchers have adopted a maturational perspective and have reached similar conclusions as to the presence of critical or sensitive periods (e.g., Abrahamsson, 2012; DeKeyser & Larson-Hall, 2005; Long, 1990; Oyama, 1976; Patkowski, 1980). Some researchers have pointed out that age effects continue into adulthood, contrary to the claim for a critical period (e.g., Birdsong & Mollis, 2001). Others have suggested that what looks like an age-related maturational decline may be accounted for by confounding factors, such as task effects, effects of L1, amount of L2 use, education or input (e.g., Bialystok & Miller, 1999; Flege, Yeni-Komshian & Liu, 1999).

The present electroencephalographical multi-speaker MMN oddball experiment was designed to study the phonological processing of German native and non-native speech sounds. Precisely, we focused on the perception of German /ɪ-iː/, /ɛ-ɛː/, /a-aː/ and the fricatives [ʃ] and [ç] in German natives (GG) and French learners of German (FG). As expected, our results showed that GG were able to discriminate all the critical vowel contrasts. In contrast, FG, despite their high L2 proficiency level, were only marginally sensitive to vowel length variations. Finally, neither GG nor FG discriminated the opposition between [ʃ] and [ç], as revealed by the absence of MMN response. This latter finding was interpreted in terms of low perceptual salience. Taken together, the present findings lend partial support to the Perceptual Assimilation Model for late bilinguals (PAM-L2) for speech perception of non-native phonological contrasts.

The study investigates the effects of grammatical gender on bilingual processing. Native speakers of Russian (a gendered language) learning English and monolingual English controls performed a self-paced reading task in English (a non-gendered language). As predicted, bilingual speakers showed delayed latencies to gendered pronouns (he or she) that were incongruent with the noun's grammatical gender in Russian, indicating that first language (L1) grammatical gender assignment can be interpreted as biological gender in nonnative (L2) processing. The L1 gender bias was only found in sentences containing animate, but not inanimate, nouns. These results speak against the syntactic mechanism being solely responsible for gender biases, but rather support a semantic transfer account due to coactivation of linguistic and conceptual features as proposed in the sex and gender hypothesis (SAGH, Vigliocco, Vinson, Paganelli & Dworzynski, 2005). Overall, the study provides clear evidence for the L1 grammatical gender bias in bilingual processing, albeit constrained by animacy.

The field of bilingual first language acquisition has focused on several important and interrelated issues: whether or not the young child acquiring two languages simultaneously differentiates his or her two languages from the onset of acquisition, what role the input plays in the acquisition of two languages, and whether the path of acquisition is similar to that of monolingual peers (see De Houwer, 1990). As a member of the DUFDE team, Natascha Müller has in previous work argued forcefully and convincingly for the bilingual child's separate development of his or her two languages, and hence how language-acquiring bilinguals behave like monolinguals. In her keynote article, Müller invokes the notion of transfer, a well-known term from research into second language acquisition, and proposes to consider transfer from the perspective of the input to which the young bilingual child is exposed. When this input is ambiguous, so that is there is variation in the input regarding one of the languages, the child will resort to transfer from the other language as a so-called relief strategy. In the following, I address the issue of cross-linguistic influence in language development and highlight the implications Müller's proposals may have for the field of bilingual first language acquisition. In conclusion I will relate these issues to the complexity of the notion of input in early bilingualism.

Mouthings, the spoken language elements in sign language discourse, are typically analysed as having a redundant, one-on-one relationship with manual signs, both semantically and temporally. We explore exceptions to this presupposed semantic and temporal congruency in a corpus of spontaneous signed conversation by deaf users of Sign Language of the Netherlands (NGT). We identify specifying mouthings (words with a different meaning than the co-occurring sign), solo mouthings (uttered while the hands are inactive) and added mouthings (words added to a signing stream without their corresponding sign), and make a sentence-level analysis of their occurrences. These non-redundant mouthings occurred in 12% of all utterances, and were made by almost all signers. We argue for the presence of a code-blending continuum for NGT, where NGT is the matrix language and spoken Dutch is blended in, in various degrees. We suggest expansion of existing code-mixing models, to allow for description of bimodal mixing.

This study describes how Turkish and Moroccan adults acquire Dutch possessive clauses in which the verb have expresses the possessive relationship. The acquisition process is explained within the framework of recent generative theory in which have-clauses are assumed to be copular locative constructions. In this theory, predicate inversion of the locative PP and incorporation of the locative P0 into a be-copula are the main characteristics of a possessive have-clause. Assuming that all linguistic knowledge of the L1 is present, L2 learners rely on it from the earliest stages, irrespective of whether this L1 knowledge is parameter-related or not. The results confirm such a “conservation” viewpoint, which accounts for how the possessive relationship is expressed in the earliest stages and why these learners have their language-specific difficulties in discovering the target have-construction. The results corroborate the conservation effect of both parametrized linguistic knowledge, viz., the strong features triggering predicate inversion, and non-parametrized knowledge, viz., knowledge of syntax, morphology and morphological realization rules, and properties of lexical items.

Any person who has taught Spanish as a second language or who has interacted with a non-native speaker of Spanish can easily tell that mastering the correct use of the copulas ser and estar is very difficult in both spoken and written production. But L2 learners are not alone. The Spanish copulas also present difficulty and frustration for L2 instructors of Spanish, since most pedagogical explanations of the uses of ser and estar provided in textbooks are incomplete and inaccurate. However, the acquisition of copular constructions has not received the attention it deserves in the acquisition literature, making a special issue of Bilingualism: Language and Cognition dedicated to this topic particularly welcome. A reason for the scarcity of research in this area may be related to both the linguistic complexity of Spanish ser and estar and the inadequacy of many available theoretical treatments to explain their complementary distribution. Although constructions with ser and estar are highly frequent in the input, they are grammatically quite intricate, straddling between the levels of morphology, syntax, semantics and pragmatics. Accordingly, Bruhn de Garavito and Valenzuela correctly frame their study within the current debate on interface vulnerability in language development in general, and in adult L2 acquisition in particular (Sorace, 2004; White, in press). In a nutshell, grammatical areas which require the integration of different levels of linguistic knowledge (e.g., syntax–discourse, syntax–morphology, morphology–semantics, etc.) for processing, production, or interpretation, show developmental delays and instability in monolingual and bilingual acquisition. In the case of monolingual acquisition, instability or non-target-like behavior is temporary, but in L2 grammars, instability can persist up to very advanced levels of proficiency, eventually leading to fossilization.

Extending the paradigm in L1 acquisition, scholars have begun to investigate whether participants’ domain-general ability to represent, encode, and integrate spectral and temporal dimensions of sounds (i.e., auditory processing) could be a potential determinant of the outcomes of post-pubertal L2 speech learning. The current study set out to test the hypothesis that auditory processing makes a unique contribution to L2 speech acquisition, for 70 Japanese classroom learners of English with different levels of L2 proficiency when biographical backgrounds (length of instruction and immersion) and memory abilities (working, declarative, and procedural memory) are controlled for. Auditory processing loaded onto modality-general capacities to represent and incorporate anchor stimuli (relative to target stimuli) into long-term memory in an implicit fashion, but dissociated from explicit abilities to remember, associate, and elaborate sensory information. Auditory processing explained a small-to-medium amount of variance in L2 speech learning, even after the other potentially confounding variables were statistically factored out.