In Press
Anderson, J. A., Chung, A. F. - Y., Bellana, B., Luk, G., & Bialystok, E. (In Press). Language and cognitive control networks in bilinguals and monolinguals. Neuropsychologia.Abstract
Neuroimaging studies have reported overlapping neural circuits for cognitive control when engaging in tasks that involve verbal and nonverbal stimuli in young adult bilinguals. However, no study to date has examined the neural basis of verbal and nonverbal task switching in both monolinguals and bilinguals due to the inherent challenge of testing verbal task switching with monolinguals. Therefore, it is not clear whether the finding for overlapping networks is unique to bilingualism or indicative of general cognitive control. To address this question, the current study compared functional neural activation for young adults who were bilingual speakers of English and French or monolingual English speakers who had limited French learning experience (“functional monolinguals”) on verbal and nonverbal task switching. Analyses showed common variance explaining general cognitive control in task switching across verbal and nonverbal domains for both groups, in line with the explanation that task switching involves general cognitive control, as well as unique brain regions recruited by monolinguals and bilinguals. Specifically, beyond the processing common to the tasks, monolinguals also recruited distinct networks for each of verbal and nonverbal switching but bilinguals used a common shared network. Thus, the domain-general aspect of switching is different for monolinguals and bilinguals.
Yamasaki, B., & Luk, G. (In Press). Eligibility for special education in elementary school: The role of diverse language experiences. Language, Speech, and Hearing Services in Schools.Abstract

Purpose: We examined the association between language experience and elementary students' eligibility for special education in Massachusetts.

Method: A secondary descriptive data analysis was conducted on the anonymized demographic data obtained from the Massachusetts Department of Elementary and Secondary Education. Third, fourth, and fifth grade students were categorized into native English speakers, English-proficient bilingual students, and emerging bilinguals. Free-/reduced lunch status was also considered. Proportions of students eligible for Autism, Communication Disorders, and Specific Learning Disabilities (including those with dyslexia) were calculated.

Results: A strong association was observed between students' language backgrounds and whether they were eligible for free-/reduced lunch. Children eligible for free-/reduced lunch were more likely to be eligible for special education. Relative to native English speakers, English proficient bilingual students were less likely to be considered eligible for special education. However, for emerging bilinguals, eligibility was lower in third graders but increased in fourth and fifth graders. This observation was most apparent in the category of Specific Learning Disabilities.

Conclusions: Students from diverse language backgrounds and low-income backgrounds were disproportionately represented in special education. More substantial research-practice partnerships are warranted to understand how bilingual experience and socioeconomic status interacts with eligibility for special education conditions in public school settings.

Luk, G., & Kroll, J. (Forthcoming). Bilingualism and education: Bridging cognitive science research to language learning. In J. Dunlosky & K. Rawson (Ed.), Cambridge Handbook of Cognition and Education . Cambridge University Press.Abstract
  1. Research in psychology has demonstrated positive cognitive and differential neural consequences of bilingualism in children and adults. For educators, these findings may not always be transparent because of the different contexts between research and practice. In this chapter, the authors take a first step towards creating a bridge between research findings on language learning and bilingualism and the contexts in which learning occurs across the lifespan, in classrooms and beyond. This chapter serves as a starting point in facilitating cross-disciplinary discussions on improving learning support for children and adults of all language backgrounds.
Whitford, V., & Luk, G. (Forthcoming). Comparing executive functions in monolinguals and bilinguals: Considerations on participant characteristics and statistical assumptions in current research. In I. Sekerina, V. Valian, & L. Spradlin (Ed.), Studies in Bilingualism. . John Benjamins.Abstract

Research on bilingualism and executive functions has primarily focused on the presence or absence of an advantage, based on group comparisons between monolinguals and bilinguals. This research rests on two assumptions: first, that participant groups are mutually exclusive, and second, that important statistical practices are upheld. These assumptions, however, are linked to participant-related characteristics and data diagnostic procedures, which are often underreported. Importantly, bilingualism is a dynamic experience, reflecting how individuals interact with their environment through different languages. This interactional experience is essential for grouping participants within studies, and for drawing comparisons across studies. This paper addresses why definitive claims based on between-group investigations of bilingualism and executive functions are insufficient, particularly when research contexts are not considered, and proposes future research directions for the field.

Surrain, S., & Luk, G. (2017). Describing bilinguals: A systematic review of labels and descriptors used in the literature between 2005-2015. Bilingualism: Language and Cognition. . Publisher's VersionAbstract
Recent years have seen a surge in research comparing bilinguals to monolinguals, yet synthesizing this literature is complicated by the diversity of language and social backgrounds behind these dichotomous labels. The current study examines the labels and descriptions reported in 186 studies comparing bilinguals and monolinguals published between 2005–2015 in order to understand how bilingualism has been operationalized and to describe the degree to which different facets of bilingual experience are reported. Proficiency and usage were the most frequently reported features (77% and 79%), followed by language history (67%) and the language of schooling (60%). However, less than half of the studies measured proficiency objectively or reported proportional usage, and even less – 30% – described the sociolinguistic context from which the sample was drawn. Given the increase in language contact due to globalization, more transparent and comprehensive reporting of participant characteristics is critical to building our understanding of how bilingualism affects experience.
Luk, G. (2017). Bilingualism. In B. Hopkins, E. Geangu, & S. Linkenauger (Ed.), The Cambridge Encyclopedia of Child Development (2nd ed. pp. 385-391) . Cambridge University Press. Publisher's Version
Pliatsikas, C., & Luk, G. (2016). Executive control in bilinguals: A concise review on fMRI studies. Bilingualism: Language and Cognition. , 19, 699-705. Publisher's VersionAbstract

The investigation of bilingualism and cognition has been enriched by recent developments in functional magnetic resonance imaging (fMRI). Extending how bilingual experience shapes cognition, this review examines recent fMRI studies adopting executive control tasks with minimal or no linguistic demands. Across a range of studies with divergent ages and language pairs spoken by bilinguals, brain regions supporting executive control significantly overlap with brain regions recruited for language control (Abutalebi & Green, this issue). Furthermore, limited but emerging studies on resting-state networks are addressed, which suggest more coherent spatially distributed functional connectivity in bilinguals. Given the dynamic nature of bilingual experience, it is essential to consider both task-related functional networks (externally-driven engagement), and resting-state networks, such as default mode network (internal control). Both types of networks are important elements of bilingual language control that relies on domain-general executive control.

Guerrero, S. L., Smith, S., & Luk, G. (2016). Home language usage and executive function in bilingual preschoolers. In Cognitive Control and Consequences of Multilingualism. (pp. 351-374) . John Benjamins. Publisher's VersionAbstract

Executive function (EF) is fundamental to successful learning and goal-directed behavior in both adults and children. Bilingual experience has been shown to facilitate EF across the lifespan, likely due to the increased cognitive demand required for managing multiple languages on a daily basis. Building on previous research that primarily compared monolinguals and bilinguals categorically, the present study examined whether variation in non-dominant language usage moderates the developmental trajectory of EF in a sample of 71 heterogeneous Spanish-English bilingual preschoolers. Using a general linear model, we found a significant interaction between the proportions of Spanish use, chronological age and performance on an EF task. Results suggest that daily bilingual usage moderates preschoolers’ development in EF. Bilingualism is a multidimensional experience, and for developing children, daily usage is an important quantifiable indicator of bilingualism when considering EF. Research and educational implications are discussed in light of these findings.

Luk, G., & Christodoulou, J. A. (2016). Assessing and Understanding the Needs of Dual-Language Learners. In N. Lesaux & S. Jones (Ed.), The Leading Edge of Early Childhood Education: Linking Science To Policy for A New Generation of Pre-K (pp. 67-90) . Cambridge, MA, Harvard Education Press. Publisher's Version
Luk, G., & Pliatsikas, C. (2016). Converging diversity to unity: Commentary on The neuroanatomy of bilingualism. Language, Cognition, and Neuroscience , 19, 349-352. Publisher's Version
Dunn, E. C., Busso, D. S., Raffeld, M. R., Nelson, C. A., Smoller, J. W., Doyle, A. E., & Luk, G. (2016). Does developmental timing of exposure to child maltreatment predict memory performance in adulthood? Results from a large, population-based sample. Child Abuse & Neglect. Publisher's VersionAbstract

Although maltreatment is a known risk factor for multiple adverse outcomes across the lifespan, its effects on cognitive development, especially memory, are poorly understood. Using data from a large, nationally representative sample of young adults (Add Health), we examined the effects of physical and sexual abuse on working and short-term memory in adulthood. We examined the association between exposure to maltreatment as well as its timing of first onset after adjusting for covariates. Of our sample, 16.50% of respondents were exposed to physical abuse and 4.36 % to sexual abuse by age 17. An analysis comparing unexposed respondents to those exposed to physical or sexual abuse did not yield any significant differences in adult memory performance. However, two developmental time periods emerged as important for shaping memory following exposure to sexual abuse, but in opposite ways. Relative to non-exposed respondents, those exposed to sexual abuse during early childhood (ages 3-5), had better number recall and those first exposed during adolescence (ages 14-17) had worse number recall. However, other variables, including socioeconomic status, played a larger role (than maltreatment) on working and short-term memory. We conclude that a simple examination of "exposed" versus "unexposed" respondents may obscure potentially important within-group differences that are revealed by examining the effects of age at onset to maltreatment.

Grady, C., Luk, G., Craik, F. I. M., & Bialystok, E. (2015). Brain network activity in monolingual and bilingual older adults. Neuropsychologia , 66, 170-181. Publisher's VersionAbstract

Bilingual older adults typically have better performance on tasks of executive control (EC) than do their monolingual peers, but differences in brain activity due to language experience are not well understood. Based on studies showing a relation between the dynamic range of brain network activity and performance on EC tasks, we hypothesized that life-long bilingual older adults would show increased functional connectivity relative to monolinguals in networks related to EC. We assessed intrinsic functional connectivity and modulation of activity in task vs. fixation periods in two brain networks that are active when EC is engaged, the frontoparietal control network (FPC) and the salience network (SLN). We also examined the default mode network (DMN), which influences behavior through reduced activity during tasks. We found stronger intrinsic functional connectivity in the FPC and DMN in bilinguals than in monolinguals. Although there were no group differences in the modulation of activity across tasks and fixation, bilinguals showed stronger correlations than monolinguals between intrinsic connectivity in the FPC and task-related increases of activity in prefrontal and parietal regions. This bilingual difference in network connectivity suggests that language experience begun in childhood and continued throughout adulthood influences brain networks in ways that may provide benefits in later life.

Olsen, R. K., Pangelinan, M. M., Bogulski, C., Chakravarty, M. M., Luk, G., Grady, C., & Bialystok, E. (2015). The effect of lifelong bilingualism on regional grey and white matter volume. Brain Research , 1612, 128-139. Publisher's VersionAbstract

Lifelong bilingualism is associated with the delayed diagnosis of dementia, suggesting bilingual experience is relevant to brain health in aging. While the effects of bilingualism on cognitive functions across the lifespan are well documented, less is known about the neural substrates underlying differential behaviour. It is clear that bilingualism affects brain regions that mediate language abilities and that these regions are at least partially overlapping with those that exhibit age-related decline. Moreover, the behavioural advantages observed in bilingualism are generally found in executive function performance, suggesting that the frontal lobes may also be sensitive to bilingualism, which exhibit volume reductions with age. The current study investigated structural differences in the brain of lifelong bilingual older adults (n=14, mean age=70.4) compared with older monolinguals (n=14, mean age=70.6). We employed two analytic approaches: 1) we examined global differences in grey and white matter volumes; and, 2) we examined local differences in volume and cortical thickness of specific regions of interest previously implicated in bilingual/monolingual comparisons (temporal pole) or in aging (entorhinal cortex and hippocampus). We expected bilinguals would exhibit greater volume of the frontal lobe and temporal lobe (grey and white matter), given the importance of these regions in executive and language functions, respectively. We further hypothesized that regions in the medial temporal lobe, which demonstrate early changes in aging and exhibit neural pathology in dementia, would be more preserved in the bilingual group. As predicted, bilinguals exhibit greater frontal lobe white matter compared with monolinguals. Moreover, increasing age was related to decreasing temporal pole cortical thickness in the monolingual group, but no such relationship was observed for bilinguals. Finally, Stroop task performance was positively correlated with frontal lobe white matter, emphasizing the importance of preserved white matter in maintaining executive function in aging. These results underscore previous findings implicating an association between bilingualism and preserved frontal and temporal lobe function in aging.

Pollack, C., Luk, G., & Christodoulou, J. (2015). A meta-analysis of functional reading systems in typically developing and struggling readers across different alphabetic languages. Frontiers in Psychology , 6. Publisher's VersionAbstract

Functional neuroimaging research has identified multiple brain regions supporting reading-related activity in typical and atypical readers across different alphabetic languages. Previous meta-analyses performed on these functional magnetic resonance imaging findings typically report significant between-group contrasts comparing typical readers and readers with reading difficulty or a clinical diagnosis of developmental dyslexia. In order to advance our understanding of cross-linguistic convergence of reading-related brain activations for these reader groups, analyses using activation likelihood estimation were carried out separately for typical and atypical readers who ranged from children to adults. Contrasts were analyzed for tasks involving rhyming or reading of letter or word stimuli presented visually in English, Dutch, Italian, German, French, or Norwegian. Typical readers showed reliable activation in only left lateralized regions, including the inferior frontal area, precentral area and middle temporal gyrus. Atypical readers also showed activation in the left inferior frontal area and precentral region, in addition to significant activations in the right hemisphere, including the superior, medial and inferior frontal regions, lingual gyrus and the inferior occipital area. These results distinguish between typical and atypical reader group activations, showing common and distinct regions of activation when engaged in reading-related activities, extending previous meta-analyses on identifying brain regions relevant to reading to include cross-linguistic analyses for alphabetic scripts. Results support the universality of a signature pattern of brain activation in developmental dyslexia across alphabetic languages.

Friesen, D. C., Luo, L., Luk, G., & Bialystok, E. (2015). Proficiency and control in verbal fluency performance across the lifespan for monolinguals and bilinguals. Language, Cognition and Neuroscience , 30 (3), 238-250. Publisher's VersionAbstract

The verbal fluency task is a widely used neuropsychological test of word retrieval efficiency. Both category fluency (e.g., list animals) and letter fluency (e.g., list words that begin with F) place demands on semantic memory and executive control functions. However, letter fluency places greater demands on executive control than on category fluency, making this task well suited to investigating potential bilingual advantages in word retrieval. Here we report analyses on the category and letter fluency for bilinguals and monolinguals at four ages, namely, 7-year-olds, 10-year-olds, young adults and older adults. Three main findings emerged: (1) verbal fluency performance improved from childhood to young adulthood and remained relatively stable in late adulthood; (2) beginning at 10-year-olds, the executive control requirements for letter fluency were less effortful for bilinguals than monolinguals, with a robust bilingual advantage on this task emerging in adulthood and (3) an interaction among factors showed that category fluency performance was influenced by both age and vocabulary knowledge, but letter fluency performance was influenced by bilingual status.

Luk, G. (2015). Who are the bilinguals (and monolinguals)? Bilingualism: Language and Cognition , 18, 35-36. Publisher's VersionAbstract

In the keynote article, “Bilingualism and Cognition”, Valian (2014) has reviewed current research on comparing executive function (EF) in monolingual and bilingual individuals across the lifespan. The conclusion is that there are inconsistent EF advantages from bilingualism and all other cognitive challenging activities primarily because individual differences in these cognitive challenging experiences may collectively attribute to superior EF resulting in inconsistent EF benefit attributable to a single experience. In essence, variability in study participants’ experience and tasks contributes to the inconsistency in the behavioral outcomes observed in monolinguals and bilinguals. Notably, Valian suggests that monolinguals may also engage in other cognitively challenging activities, which have not been accounted for in individual studies, thereby resulting in improved EF similar in magnitude to that related to bilingual experience. Although it was not specified which cognitively challenging activity is more likely to be engaged by monolinguals more than by bilinguals, the question at heart is: is there an EF advantage that can be specifically attributed to bilingual experience? The review addressed in the keynote demonstrates seemingly inconsistent patterns of results. In this commentary, I would like to suggest that, in addition to task measurements, individual bilingual experience is dynamic and multifaceted. Moreover, bilingual experience varies in different communities. Consequently, one potential source of explanation for the inconsistent results in between-group EF performances is the characteristics of the bilinguals (and monolinguals) and their social environments included in these studies.

Luk, G. & Bialystok, E. (2013). Bilingualism is not a categorical variable: Interaction between language proficiency and usage. Journal of Cognitive Psychology , 25, 605-621. HHS Public AccessAbstract

Bilingual experience is dynamic and poses a challenge for researchers to develop instruments that capture its relevant dimensions. The present study examined responses from a questionnaire administered to 110 heterogeneous bilingual young adults. These questions concern participants’ language use, acquisition history and self-reported proficiency. The questionnaire responses and performances on standardized English proficiency measures were analyzed using factor analysis. In order to retain a realistic representation of bilingual experience, the factors were allowed to correlate with each other in the analysis. Two correlating factors were extracted, representing daily bilingual usage and English proficiency. These two factors were also related to self-rated proficiency in English and non-English language. Results were interpreted as supporting the notion that bilingual experience is composed of multiple related dimensions that will need to be considered in assessments of the consequences of bilingualism.

Luk, G. (2012). Bialystok, Ellen. In The Encyclopedia of Applied Linguistics. . Wiley Online Library. Publisher's VersionAbstract

Ellen Bialystok (1948– ) is a Distinguished Research Professor in the Department of Psychology at York University, Toronto, Canada. She has bridged studies of language and cognition through her investigation of bilingualism. Her pioneering interdisciplinary research examines the cognitive consequences of bilingualism both in linguistic and nonlinguistic domains across the lifespan. Most notably, Professor Bialystok has reported a bilingual advantage in tasks assessing executive function, which is a set of skills that are necessary for planning, cognitive flexibility, suppressing distracting information, and selectively attending to relevant information. These research findings have significant implications for education, linguistics, cognitive science, psychology, and neurology.

Luk, G., Green, D. W., Abutalebi, J., & Grady, C. L. (2012). Cognitive control for language switching in bilinguals: A quantitative meta-analysis of functional neuroimaging studies. Language and Cognitive Processes , 27 (10), 1479-1488. WebsiteAbstract

In a quantitative meta-analysis, using the activation likelihood estimation method, we examined the neural regions involved in bilingual cognitive control, particularly when engaging in switching between languages. The purpose of this study was to evaluate the bilingual cognitive control model originally proposed as a qualitative analysis of functional neuroimaging studies. After reviewing 128 peer-reviewed articles, 10 neuroimaging studies met our inclusion criteria and in each study, bilinguals switched between languages in response to cues. We isolated regions involved in voluntary language switching, by including reported contrasts between the switching conditions and high-level baseline conditions involving similar tasks but requiring the use of only one language. Eight brain regions showed significant and reliable activation: left inferior frontal gyrus, left middle temporal gyrus, left middle frontal gyrus, right precentral gyrus, right superior temporal gyrus, midline pre-supplementary motor area, and bilateral caudate nuclei. This quantitative result is consistent with bilingual aphasia studies that report switching deficits associated with lesions to the caudate nuclei or prefrontal cortex. It also extends the previously reported qualitative model. We discuss the implications of the findings for accounts of bilingual cognitive control.

Bialystok, E., & Luk, G. (2012). Receptive vocabulary differences in monolingual and bilingual adults. Bilingualism: Language and Cognition , 15, 397-401.Abstract

English receptive vocabulary scores from 797 monolingual and 808 bilingual participants between the ages of 17 and 89 years old were aggregated from 20 studies to compare standard scores across language groups. The distribution of scores was unimodal for both groups but the mean score was significantly different, with monolinguals obtaining higher standard scores than bilinguals. Consistent with previous research, older adults had higher vocabulary scores than younger adults. The results are discussed in terms of the implications for theoretical conceptions of linguistic processing and clinical diagnosis in bilingual populations.