Lexical Frequency Research Articles

Effects of MOOC and video conferencing deliveries on vocabulary usage and learning strategies

While vocabulary learning strategies (VLSs) have primarily been taught in physical classroom settings, the potential for applying strategy training in an online environment remains under-explored. With the rising acceptance of remote education, there is a need to investigate the impacts of applying strategy training in online contexts. Hence, this study explores the effects of online deliveries on VLSs and vocabulary usage in writing among adult English as second language (ESL) learners via massive open online course (MOOC) and video conferencing platforms. A total of 50 pre-intermediate ESL learners completed a 5-week VLSs course on a MOOC while 44 students learnt from the instructor synchronously using Microsoft Teams. The data comprised questionnaires and learners’ compositions, which were collected before and after treatment. The data analysis procedures involved Lextutor’s version of lexical frequency profiling (LFP), descriptive and inferential statistics. The results revealed that there was a significant increase of usage in all categories of the VLSs after the course for both groups. Additionally, the effects of VLSs instruction on vocabulary usage could be reflected in both groups’ writing though the choice of words might have been task-influenced. The findings from this study could yield useful insights on online vocabulary learning for ESL instructors and learners.

Lexical frequency and target language input in the primary languages classroom

ABSTRACT This paper presents an exploratory study of L2 input in the primary languages classroom. Teacher talk in 33 videorecorded lessons taught to Year 3 French beginners by a specialist teacher of French was analysed, in order to document the extent and nature of L2 vocabulary input. Further analyses compared the lexis of teacher talk in this primary setting with high-frequency wordlists derived from two reference corpora designed to support the teaching of L2 French. Results showed that children were exposed to c 45,000 words (tokens) of French, reflecting a teacher vocabulary of c 650 lemmas. Intentionally taught lexis such as foods or animal names typically received massed practice, not always supplemented by distributed practice. The teachers’ partial but consistent use of French for classroom management contributed to a well-balanced distribution of word classes. There was considerable overlap with both reference wordlists, and divergence could largely be explained by the teacher’s choice of topics, and incidental use of French to personalise and engage childrens’ individual interests, as well as for classroom management purposes. In discussion, the need for careful planning and management of vocabulary instruction is highlighted, as well as the significant potential of L2 classroom management to enrich lexical input.

Cross-Linguistic and Multicultural Considerations in Evaluating Bilingual Adults With Aphasia.

The current study delineated a clinical and theoretical framework that clinicians and researchers can use to guide the assessment of bilingual aphasia at morphosyntactic, lexical-semantic, and phonological levels of language processing. This tutorial outlines cross-linguistic and multicultural considerations that should be addressed in evaluating bilingual adults with aphasia (BWAs). At the morphosyntactic level, we presented three features that should be taken into account when evaluating linguistic symptoms in languages considering whether they are typologically similar or dissimilar: word order, pro(noun)-drop, and morphological inflections of verbs. We suggest that clinicians need to conduct additional error analyses that reflect typological differences in syntactic templates, argument-deletion phenomena, and morphological inflections to better understand linguistic characteristics of impairments arising from the interactions of the two languages that may differ in many ways. At the lexical-semantic level, we addressed three cross-linguistic features that may impact naming performance in BWAs: cognates, lexical frequency, and semantic typicality. The presence of cognates between the two languages can lead to differential interpretations of naming performance. In addition, the same lexical items may exhibit varying lexical frequency and typicality across languages due to cultural and linguistic differences. We suggest that clinicians should thoroughly prepare the testing items considering the linguistic distance. Finally, we emphasized differences in segmental and suprasegmental features of phonology that could contribute to cross-linguistic phenomena during assessment of two or more languages. This cross-linguistic assessment framework contributes to a better understanding of linguistic impairments and communication difficulties experienced by BWAs. This framework can be utilized in current clinical practice to facilitate culturally and linguistically appropriate assessment and treatment approaches for BWAs.

High frequency post-pause word choices and task-dependent speech behavior characterize connected speech in individuals with mild cognitive impairment.

Alzheimer's disease (AD) is characterized by progressive cognitive decline, including impairments in speech production and fluency. Mild cognitive impairment (MCI), a prodrome of AD, has also been linked with changes in speech behavior but to a more subtle degree. This study aimed to investigate whether speech behavior immediately following both filled and unfilled pauses (post-pause speech behavior) differs between individuals with MCI and healthy controls (HCs), and how these differences are influenced by the cognitive demands of various speech tasks. Transcribed speech samples were analyzed from both groups across different tasks, including immediate and delayed narrative recall, picture descriptions, and free responses. Key metrics including lexical and syntactic complexity, lexical frequency and diversity, and part of speech usage, both overall and post-pause, were examined. Significant differences in pause usage were observed between groups, with a higher incidence and longer latencies following these pauses in the MCI group. Lexical frequency following filled pauses was higher among MCI participants in the free response task but not in other tasks, potentially due to the relative cognitive load of the tasks. The immediate recall task was most useful at differentiating between groups. Predictive analyses utilizing random forest classifiers demonstrated high specificity in using speech behavior metrics to differentiate between MCI and HCs. Speech behavior following pauses differs between MCI participants and healthy controls, with these differences being influenced by the cognitive demands of the speech tasks. These post-pause speech metrics can be easily integrated into existing speech analysis paradigms.

Neural tracking of speech acoustics in noise is coupled with lexical predictability as estimated by large language models.

Adults heard recordings of two spatially separated speakers reading newspaper and magazine articles. They were asked to listen to one of them and ignore the other, and EEG was recorded to assess their neural processing. Machine learning extracted neural sources that tracked the target and distractor speakers at three levels: the acoustic envelope of speech (delta- and theta-band modulations), lexical frequency for individual words, and the contextual predictability of individual words estimated by GPT-4 and earlier lexical models. To provide a broader view of speech perception, half of the subjects completed a simultaneous visual task, and the listeners included both native and non-native English speakers. Distinct neural components were extracted for these levels of auditory and lexical processing, demonstrating that native English speakers had greater target-distractor separation compared to non-native English speakers on most measures, and that lexical processing was reduced by the visual task. Moreover, there was a novel interaction of lexical predictability and frequency with auditory processing; acoustic tracking was stronger for lexically harder words, suggesting that people listened harder to the acoustics when needed for lexical selection. This demonstrates that speech perception is not simply a feedforward process from acoustic processing to the lexicon. Rather, the adaptable context-sensitive processing long known to occur at a lexical level has broader consequences for perception, coupling with the acoustic tracking of individual speakers in noise.Significance Statement In challenging listening conditions, people use focused attention to help understand individual talkers and ignore others, which changes their neural processing for speech at auditory through lexical levels. However, lexical processing for natural materials (e.g., conversations, audiobooks) has been difficult to measure, because of limitations of tools to estimate the predictability of individual words in longer discourses. The present investigation uses a contemporary large language model, GPT-4, to estimate word predictability, and demonstrates that listeners make online adaptations to their auditory neural processing in accord with these predictions; neural activity more closely tracks the acoustics of the target talker when words are less predictable from the context.

Speech pauses in speakers with and without aphasia: A usage-based approach

Pauses in speech are indicators of cognitive effort during language production and have been examined to inform theories of lexical, grammatical and discourse processing in healthy speakers and individuals with aphasia (IWA). Studies of pauses have commonly focused on their location and duration in relation to grammatical properties such as word class or phrase complexity. However, recent studies of speech output in aphasia have revealed that utterances of IWA are characterised by stronger collocations, i.e., combinations of words that are often used together. We investigated the effects of collocation strength and lexical frequency on pause duration in comic strip narrations of IWA and non-brain-damaged (NBD) individuals with part of speech (PoS; content and function words) as covariate. Both groups showed a decrease in pause duration within more strongly collocated bigrams and before more frequent content words, with stronger effects in IWA. These results are consistent with frameworks which propose that strong collocations are more likely to be processed as holistic, perhaps even word-like, units. Usage-based approaches prove valuable in explaining patterns of preservation and impairment in aphasic language production.

Using semantic verbal fluency to estimate the relative and absolute vocabulary size of bilinguals: An exploratory study of children and adolescents

IntroductionThe full assessment of bilingual children often involves at least one language for which formal vocabulary tests are lacking and which the examiner does not speak. We examined, in a sample of children with typical development (TD), whether a semantic verbal fluency task, typically used in research as a measure of executive function, could be used in the place of a formal vocabulary test to estimate vocabulary knowledge when formal tests are not available. Method113 TD monolingual French speakers and TD bilinguals and with varying degrees of exposure to French, age 6 to 17 years, completed tests of vocabulary knowledge and semantic verbal fluency. A subset of 64 participants spoke French and English and were tested in both languages. Verbal fluency measures calculated using a traditional method which uses specific rules for superordinate categories and for animals of different sex and age and a simplified scoring method which simply counts all words produced, included the total number of words produced in each language, Total Vocabulary and Conceptual Vocabulary measures combining both languages, as well as analyses of lexical composition and word frequency within the study sample. ResultsLinear regressions revealed that the number of words produced predicted vocabulary size in a language-specific way, with slightly stronger predictions made by the simplified scoring method. As expected, bilinguals produced more words and more unique words in their language of greater exposure, while different exposure groups were equivalent in measures combining both languages, including their Total vocabulary and Conceptual vocabulary. Producing unusual words (infrequently produced in the study sample) indicated higher vocabulary scores. ConclusionsThis study supports the use of the verbal fluency task as a quick and simple tool to obtain a rough estimate of vocabulary size in TD monolinguals and bilinguals. This tool shows promise as well in clinical work with other populations, subject to further verification.

ANALYZING THE POLITICAL IDEOLOGIES OF TUN MAHATHIR IN TWO ERAS: A CORPUS-BASED ANALYSIS OF LEXICAL CHOICES

The ideology behind Tun Mahathir’s way of thinking always been the subject of interest for many. This research will investigate the political ideology of Tun Mahathir based on his lexical choices and words frequency in his speeches during two different Prime Minister eras and will compare the two corpora lexical choices, words frequency and political ideology that exist within.A total of 151 texts were compiled which consisted of 79 texts from the first era (2001-2003) and 72 texts from the second era (2018-2020). The comparative analysis of the two corpora were conducted through two stages, its word frequencies especially nouns to help determining lexical choices and Critical Discourse Analysis in revealing Tun Mahathir's political ideologies. The result shows some differences in word frequencies and lexical choices in both eras in which reflected Tun Mahathir's political ideology in the two eras. The word ‘negara’, a noun, has the highest frequency for both eras and yet words that were ''economy'' related has the highest frequency during the first era whereas society related was the highest during the second era. The changes in Tun Mahathir political party during the two eras may be a contributors to the changes of the lexical choices and slight changes of political ideology that occur. The changes in political landscapes and social problems in Malaysia contributes to the factor as well. Investigating Tun Mahathir's lexical choices in different speeches can help to investigate deeper into Tun Mahathir''s political ideology.

Coh-Metrix 시스템을 통한 고등학교 영어 모의시험 독해지문의 학년 내 연계성 분석

This corpus-driven research aims to examine the intra-grade continuity of reading passages within high school English mock exams, specifically the national academic achievement tests for seniors in 2023. These tests were conducted quarterly by four regional educational offices: Seoul in March, Incheon in April, Gyeonggi Province in July, and Seoul in October. A corpus of 100 reading passages, 25 from each test, was analyzed via a range of Coh-Metrix measures, including word features, lexical diversity, connectives, readability, referential cohesion, syntactic complexity, semantic cohesion, and so on. These Coh-metrix results demonstrated that there was no compelling evidence to support strong intra-grade continuity, highlighting the necessity for meticulous calibration of text difficulty, which should incrementally escalate with successive test administrations. The analysis of basic metrics, lexical frequency and diversity, syntactic complexity, and readability revealed no consistent trends across test administrations. Additionally, lexical attributes such as concreteness, familiarity, imagery, and age of acquisition did not show significant continuity. Moreover, the analysis of syntactic complexity also showed no consistent pattern. The current inconsistency in text difficulty suggests that students may not be receiving the progressive challenge needed to develop their reading comprehension skills effectively. Drawing upon these findings, theoretical and pedagogical implications are elucidated.

Spanish children spelling in English as a foreign language: Central and peripheral processes

BackgroundSpelling acquisition requires the assimilation of the regularities of the writing system, but these regularities may differ between the native and a foreign language. English spelling acquisition is a challenge for Spanish‐speaking children due to differences in the orthographic systems. The aim of this study was to examine to what extent Spanish‐speaking children use sub‐lexical and lexical information when spelling in English as a foreign language (EFL), and whether this varies across grades.MethodsTo achieve this, we administered a spelling‐to‐dictation task of monosyllabic words to children 9 to 11 years old. Spelling accuracy, written latencies, and writing durations were analysed as a function of phonology‐to‐orthography consistency, lexical frequency, word length, and the semantic knowledge that the children have of the words.ResultsResults showed differences between grades, with word length only influencing younger children. Lexical frequency, consistency, and semantic knowledge facilitated performance in older children. The cumulative exposure to English may lead to an improvement in spelling due to vocabulary growth and increased sensitivity to new spelling patterns and regularities. Such development occurs despite differences between the orthographies of the native and foreign language and even in the absence of explicit instruction in EFL spelling.ConclusionsSemantic information about words helps spelling retrieval during writing in EFL. Spanish‐speaking children develop sensitivity to English orthography and spelling patterns, evident in the older group of children.

Phase-dependent word perception emerges from region-specific sensitivity to the statistics of language

Neural oscillations reflect fluctuations in excitability, which biases the percept of ambiguous sensory input. Why this bias occurs is still not fully understood. We hypothesized that neural populations representing likely events are more sensitive, and thereby become active on earlier oscillatory phases, when the ensemble itself is less excitable. Perception of ambiguous input presented during less-excitable phases should therefore be biased toward frequent or predictable stimuli that have lower activation thresholds. Here, we show such a frequency bias in spoken word recognition using psychophysics, magnetoencephalography (MEG), and computational modelling. With MEG, we found a double dissociation, where the phase of oscillations in the superior temporal gyrus and medial temporal gyrus biased word-identification behavior based on phoneme and lexical frequencies, respectively. This finding was reproduced in a computational model. These results demonstrate that oscillations provide a temporal ordering of neural activity based on the sensitivity of separable neural populations.

Experimental increase in lexical frequency improves morphological computation of Spanish

Aims/Objectives: The present study investigates whether lexical frequency can be increased experimentally, and whether an increase in lexical frequency facilitates L2 morphological processing. Design: English L2 learners of Spanish were randomly assigned to either a treatment or control group. Both groups completed a pre/post lexical decision task containing L2 words with either two or three morphemes, and a pre/post lexical frequency task. In addition, the treatment group completed four sessions in which they read texts containing low frequency words. Data/analysis: Linear mixed models and Bayes factors were used to analyze participants’ performance. Findings/Conclusions: Both groups took significantly longer to process morphologically complex words with three than with two morphemes at pretest. While this pattern was observed also at posttest for the control group, the treatment group took roughly the same to process both types of words following training. Taken together, the findings suggest that an increased exposure to low-frequency L2 words switches learners’ morphological computation strategies from decomposition to whole word processing. Originality: While previous cross-sectional studies have assessed the role of frequency on L2 morphological decomposition, this has not been confirmed by longitudinal data. Significance/Implications: The results support hybrid word recognition models claiming that frequency modulates morphological computation.

The mirror effect in online survey data: Evidence and implications for marketing theory and strategy

AbstractThis research reveals the presence, in online survey data, of a key pattern documented in psychology lab research: the Mirror Effect. The Mirror Effect occurs when unfamiliar stimuli are unexpectedly recognized as accurately as familiar stimuli, or more accurately. Using a set of familiar and unfamiliar words (as determined by lexical frequency), we first report that we can robustly replicate psychology lab research in an online survey, detecting the Mirror Effect. We then apply the same analytical approach to surveying consumer recognition of everyday brands (supermarkets, banks and car brands). We find that unfamiliar brands can be recognized with the same level of accuracy as familiar brands, and this effect is stronger than age and gender memory biases present in the data. However, we detect a boundary condition for branded apps, which are extremely unfamiliar brands competing in highly fragmented marketplaces, so very few get downloaded or used. For these digital brands, we find a Concordant Effect, as most respondents find it difficult to recognize highly unfamiliar branded apps (i.e., those with fewer than 5000 downloads). The Mirror Effect re‐emerges for highly experienced app users. These results demonstrate the implications of a generalizable empirical pattern from cognitive psychology for branding and advertising theory. The outcomes of this research also translate into practical guidelines for brand performance measurement via online surveys, mitigating recognition memory bias for the development of marketing strategies based on more accurate interpretation of empirical evidence.

Y luego un tiburón blanco ha abrido la boca: Spanish children’s overregularization of irregular past participles

Abstract The current study investigates the influence of Age, Lexical frequency, and Language background on children’s overregularization of irregular past participles (e.g., ponido ‘put’, cf. puesto). A total of 536 past participles used in compound tenses (e.g., he escrito ‘I have written’) were extracted from child speech in online corpora from both monolingual Spanish (N = 45) and Spanish-English bilingual children (N = 2) between the ages of 3;0 and 6;11. The children overregularized 7 % of their past participles and did so more often with low-frequency participles like escrito ‘written’ than with high-frequency ones like hecho ‘done/made’. Additionally, Spanish-English bilinguals overregularized more than the monolinguals, and the bilinguals’ overregularizations persisted with age while the monolingual children’s rates decreased with age. These results demonstrate that both monolingual and bilingual children overregularize irregular past participles in the structures of interest and that their overregularizations are mediated by lexical frequency. Further, these results suggest that children must be exposed to enough examples of irregular forms before they stop applying the regular pattern. While the monolingual children who were exposed to extended amounts of Spanish retreated from participle overregularization with age, bilinguals’ rates of overregularization persisted through the ages studied. These findings indicate that children from both speaker groups follow a similar acquisitional path of irregular past participles; however, language experience predicts their rates of overregularization, and the timespan required to master the irregulars.

Complexity, frequency, and acceptability

It is sometimes argued that (certain types of) lexical frequency and constructional frequency determine how easy sentences are to process and hence, how acceptable speakers find them. Others have argued that grammatical principles interact with and often override such effects. Here, we present the results from a survey on Danish with more than 200 participants. We asked people to provide acceptability ratings of a number of sentences with varying levels of complexity, with and without extraction, including complement clauses, relative clauses, parasitic gaps, and ungrammatical sentences. We predicted structural complexity and acceptability to be negatively correlated (the more complex, the less acceptable). The results show that construction frequency and acceptability are correlated, but that zero and near-zero frequencies do not predict acceptability. However, there is indeed an even stronger inverse correlation between acceptability and structural complexity, defined as a function of independently motivated factors of syntactic structure and processing, including embedding, adjunction, extraction, and distance between filler and gap. Lexical frequency also affects acceptability, but the effects are small, and, crucially, there is no evidence in our data that ungrammatical sentences are affected by such frequency effects. Furthermore, the acceptability patterns seem to be fairly stable across participants. The results show a pattern that is consistent with an approach based on grammatical principles and processing constraints, rather than based on stochastic principles alone.

Effects of word length and frequency on word identification in second- and fifth-grade children as a function of language skills

The purpose of the current study was to examine the combined effect of word length and lexical frequency in a lexical decision task in second- and fifth-grade children with varying language skills. The participants, 47 second graders and 55 fifth graders, performed a lexical decision task in which word length and lexical frequency were manipulated orthogonally so that 32 words were short and frequent (e.g., fleur [flower]), 32 words were short and rare (e.g., navet [turnip]), 32 words were long and frequent (e.g., escalier [staircase]), and 32 words were long and rare (e.g., boussole [compass]). Language skills (phonological awareness, reading, vocabulary, and rapid automatized naming skills) were measured using standard language tests. The results showed that word length and, to a lesser extent, lexical frequency influence the speed and accuracy of word identification in different ways, depending on the children’s educational level. Furthermore, language skills were found to influence the effects of word length and frequency, differently in second- and fifth-grade children. The results are interpreted within the dual-route model of visual word recognition. The role of language skills in the implementation of these processes is also discussed.

Lexical and sub-lexical frequencies in isiXhosa-medium children’s stories

Visual word recognition in developing readers is affected by several factors, many of which are important in the design of teaching and testing materials. Among these, one well-studied factor is word frequency: more frequent words are recognised more quickly than less frequent words. Another is the presence of consonant sequences, where words containing a consonant sequence (e.g. ‘tsh’) are recognised more slowly than non-consonant-sequence-containing words of equivalent letter and phoneme length. In isiXhosa, there are currently no publicly available word frequency norms that are based on children’s literacy materials and are thus appropriate for the testing of developing readers. Publicly available information on the frequencies of particular consonant sequences, which would be valuable in the design of classroom materials, is also lacking. To address these gaps, this paper reports on the creation of a corpus of isiXhosa texts aimed at children (321 texts, 125,447 tokens, and 31,216 types), which was subsequently processed to derive (i) word frequency measures, (ii) descriptive statistics about the characteristics of the most frequent words, and (iii) information on sublexical frequency, with a focus on two-, three-, and four-consonant sequences. The findings of the article are relevant to scholars and practitioners working on literacy development and language processing in isiXhosa.

Connective Comprehension in Adults: The Influence of Lexical Transparency, Frequency, and Individual Differences

ABSTRACT The comprehension of connectives is crucial for understanding the discourse relations that make up a text. We studied connective comprehension in English to investigate whether adult comprehenders acquire the meaning and intended use of connectives to a similar extent and how connective features and individual differences impact connective comprehension. A coherence judgment study indicated that differences in how well people comprehend connectives depend on the lexical transparency but not on the frequency of the connective. Furthermore, individual variation between participants can be explained by their vocabulary size, nonverbal IQ, and cognitive reasoning style. Print exposure was not found to be relevant. These findings provide further insight into the factors that influence discourse processing and highlight the need to consider individual differences in discourse comprehension research as well as the need to examine a wider range of connectives in empirical studies of discourse markers.

Linguistic and cultural properties of the Spanish adaptation of the CAT (SP-CAT): pilot results from neurotypical subjects

ABSTRACT Introduction Aphasia assessments in languages other than English are scarce. In the case of Spanish, this scarcity includes a need for assessments with linguistic and cultural adaptations that consider dialectal varieties and cultural traits across Spanish-speaking populations. Aims of the study This study discusses the linguistic and cultural adaptation of the Comprehensive Aphasia Test (CAT) to Spanish (SP-CAT), a version that can be used in Spain and Spanish-speaking Latin American countries, and provide pilot results assessing whether performance is comparable across samples. Methods For the linguistic adaptation, we discuss considerations such as typological differences between English and Spanish, Spanish varieties, gender cues, spelling-sound regularities, transparency, and other syntax-related aspects. For the cultural adaptation, we discuss considerations such as culturally relevant items and images, and covering different Spanish varieties within the SP-CAT. The pre-testing of items for the SP-CAT included controlling variables such as name agreement of visual stimuli (examined in n=237 healthy participants), imageability (examined in n=244 healthy participants), and lexical frequency (from the Corpus of Reference of Current Spanish). We also conducted a pilot study of the SP-CAT with 82 healthy participants from Chile, Colombia, and Spain to assess differences in performance within tasks between the included countries; analysis of such differences was completed within a Bayesian framework. Results The SP-CAT provides a linguistic and cultural adaptation of the original English CAT. Item pre-testing included name agreement, lexical frequency, and imageability tests to ensure comparability with the English original version. Our pilot study confirmed that there are no clinically significant differences in performance within tasks between the included countries in healthy participants, a necessary step towards the final validation of a test for the Spanish-speaking world. Discussion The SP-CAT responds to a need to develop linguistically and culturally sensitive adaptations of assessments for Spanish-speaking people with aphasia to be used in clinical practice. Pilot results indicate that the adaptation meets the criteria to be used across Spanish varieties. In light of promising pilot results, the next phase of this study will assess the validity and reliability of the SP-CAT, providing normative data for its administration.

The interaction of central and peripheral processing in L2 handwritten production: Evidence from cross-linguistic variations

Abstract The current study explores the interplay between central and peripheral processes in second language (L2) handwriting among bilinguals with diverse orthographic backgrounds. Our investigation delves into the cross-linguistic transfer effect in Spanish–English and Chinese–English bilinguals, emphasizing lexical frequency and phoneme-grapheme (P-O) consistency in spelling-to-dictation and immediate copying tasks. Results reveal that the interaction between central and peripheral processes in L2 handwritten production is shaped by the bilinguals' native language (L1) orthographic characteristics. Spanish–English bilinguals exhibited sensitivity to P-O consistency and the spread of this effect from central to peripheral processes throughout both tasks. Conversely, Chinese–English bilinguals showed heightened sensitivity to lexical frequency during orthographic planning and motor execution, particularly in the immediate copying task. In a broader context, these findings suggest that the parallel and cascading coordination of the L2 writing system is modulated by cross-linguistic variations. The implications of our findings hold relevance for handwriting production and bilingualism research.