Bilingual Anglophones on the English Version of the
Dépistage Cognitif de Québec (DCQ): A New Screening
Tool for Atypical Dementia
Mémoire
Marianne Levesque
Maîtrise en psychologie - avec mémoire
Maître ès arts (M.A.)
Québec, Canada
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Résumé
Les capacités cognitives des individus monolingues et des individus bilingues peuvent différer sur diverses tâches cognitives impliquant la mémoire, les fonctions exécutives et le langage. Comme la littérature scientifique est divisée sur ce sujet, il est de plus en plus important de valider les nouveaux outils de dépistage cognitif auprès de l’ensemble de ces groupes linguistiques divers. Dans le cas contraire, les évaluations cognitives pourraient faire l’objet d’une mauvaise interprétation pouvant entraîner des diagnostics erronés. Le Dépistage Cognitif de Québec (DCQ, www.dcqtest.org) est un nouvel outil cognitif récemment développé à la Clinique Interdisciplinaire de Mémoire de Québec (CIME) et conçu spécifiquement pour dépister les démences atypiques. La présente étude avait comme objectif de comparer des personnes âgées et en bonne santé anglophones monolingues et bilingues sur ce nouveau test. Le but était de comparer la performance de ces deux groupes sur leurs scores totaux au DCQ et sur les cinq index de l’outil : mémoire, fonctions visuospatiales, exécutives, langage et comportement. Les résultats ont montré un avantage statistiquement significatif pour les participants bilingues sur l’index du langage, contribuant à un avantage significatif pour ce groupe sur leurs scores totaux au DCQ. Bien que ces différences n’étaient plus significatives après une correction de Bonferroni, cette étude souligne l’importance d’identifier et de caractériser la diversité linguistique avant d’utiliser de nouveaux outils de dépistage en milieu clinique. Les avantages cognitifs potentiels chez les bilingues devraient être considérés lors de l’interprétation des résultats et explicitement discutés dans les rapports neuropsychologiques, même lorsque les études portent sur des adultes en bonne santé. Des études similaires avec des groupes de patients variés et d’autres types d’outils de dépistage cognitif devraient être menées, en particulier
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pour examiner plus en détail les différences entre les personnes monolingues et bilingues sur les tâches linguistiques.
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Abstract
Cognitive abilities between monolingual and bilingual individuals may differ on various cognitive tasks involving memory, executive functions and language. As the literature is divided on this topic, it is increasingly important to validate new cognitive screening tools among linguistically diverse groups to account for possible monolingual or bilingual advantages. Otherwise, assessments could be subject to misinterpretation, leading to inaccurate diagnoses. The English version of the Dépistage Cognitif de Québec (DCQ,
www.dcqtest.org) recently developed at the Clinique Interdisciplinaire de Mémoire de Québec (CIME), is one of these new cognitive tools designed specifically for better recognition of atypical dementia. The current study aimed to compare healthy older monolingual and bilingual anglophones on this new test to assess any possible differences that could lie between groups on the total DCQ scores and each of the five DCQ indexes: Memory, Visuospatial, Executive, Language and Behavioural. The results showed a statistically significant advantage for the bilingual participants on the Language Index, which contributed to the significant bilingual advantage on the DCQ total scores. Even though these results were no longer significant after a Bonferroni correction, and even if no significant differences between groups were found on any of the other indexes, this study highlights the importance of identifying and characterizing linguistic diversity before using new screening tools in clinical settings. Potential cognitive advantages in bilingual participants, even in healthy older adults, should be considered when interpreting test data and explicitly discussed in neuropsychological reports. Similar studies with patient groups and with other types of cognitive screening tools should be conducted, especially to further examine the differences between groups on language-related tasks.
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Table of contents
Résumé ... ii
Abstract ... iv
Table of contents ... v
List of tables ... vii
List of figures ... viii
Acknowledgments ... ix
Preface ... x
Introduction ... 1
The English Validation of the DCQ in Linguistically Diverse Anglophones ... 5
The Importance of Normative Data for Both Monolingual and Bilinguals ... 7
A Bilingual Advantage on Cognitive Tests in Healthy Older Adults ... 8
No Cognitive Advantage between Monolingual and Bilingual Older Adults ... 12
A Monolingual Advantage on Cognitive Tests in Older Adults ... 14
Inconsistencies ... 15
Objectives of the Current Study ... 18
Chapter 1: Article ... 20 1.1 Résumé ... 21 1.2 Abstract ... 23 Introduction ... 24 Methods ... 28 Participants ... 28 Materials ... 28
Montreal Cognitive Assessment (MoCA) ... 28
Language Experience and Proficiency Questionnaire (LEAP-Q) ... 28
Dépistage Cognitif de Québec (DCQ; www.dcqtest.org) ... 29
Procedure ... 30
Statistical Analysis ... 31
Results ... 32
Demographics ... 32
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Discussion ... 34
A Bilingual Advantage for the Overall DCQ ... 34
A Bilingual Advantage for the DCQ’s Language Index ... 35
The Absence of a Monolingual or Bilingual Advantage on All Other Indexes ... 37
Limitations ... 38
The Future Clinical Use of the DCQ ... 40
References ... 41
Conclusion ... 55
References... 63
Appendix A ... 73
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List of tables
Table 1. Summary of studies looking at the differences between monolingual and bilingual healthy older adults on tasks measuring memory, executive functions, and language…….47 Table 2. Descriptive data for the monolingual and bilingual groups………51 Table 3. Welch’s t and Mann-Whitney U tests conducted to compare monolingual and bilingual groups on their age, education, MoCA scores, Memory Index, Visuospatial Index, Executive Function Index, Language Index, Behavioural Index, and Total DCQ scores…52
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List of figures
Figure 1. Box plot of monolingual and bilingual group scores (out of 28 points) on the Language Index of the Dépistage Cognitif de Québec (DCQ)……….………53 Figure 2. Box plot of monolingual and bilingual group scores (out of 100 points) on the Dépistage Cognitif de Québec (DCQ) total scores………...54
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Acknowledgments
I would like to take the opportunity to express my deepest gratitude to the people who contributed to the completion of this project through their support, feedback, and guidance. First, I would like to give a heartfelt thank you to my outstanding research supervisor Dr. Marie-Christine Ouellet. Since day one, I have always felt welcomed in her laboratory. Dr. Ouellet has continuously made sure that I had all the necessary tools to pursue my research project. Thanks to her guidance and her support, I was able to carry out the completion of my master’s degree and evolve professionally, as well as personally.
I would also like to thank my co-supervisor, Dr. Robert Jr. Laforce, for his encouragement and support throughout my degree. His recommendations and thoughtful insight have always been much appreciated. I would also like to thank him for the opportunity I was given to work on the Dépistage Cognitif de Québec, a project that I hold close to heart.
A very special thank you to my parents, my sister and to Arthur, who have never stopped supporting me through the ups and downs, the frustrations, and the lack of motivation (especially during the pandemic). Your continuous belief in my accomplishments has brought me to where I am today.
Finally, I would like to dedicate this master’s thesis to my grandfather who has Alzheimer’s disease, and to my grandmother and their children, who have always done their best to understand this neurodegeneration disorder and advocate for better research funding and support for all those affected.
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Preface
This master’s thesis will be submitted to l’École de psychologie de l’Université Laval, Québec, to complete the last requirements of the master’s program in psychology and to obtain my degree. I am the primary author of this thesis, which was co-supervised by Dr. Marie-Christine Ouellet and Dr. Robert Jr. Laforce.
Having taken part in the multicentric validation of the English DCQ with Dr. Laforce’s team, I suggested a research question for my thesis in relation to this validation and in line with my personal interests on the topic of bilingualism. Participant recruitment was possible through Dr. Laforce’s many partnerships with institutions around North America and data collection was facilitated by the help of my student colleagues at the Clinique Interdisciplinaire de la Mémoire du CHU de Québec. Following participant recruitment and testing, I personally analyzed and interpreted the data. This statistical analysis was verified by Dr. Ouellet and by a professional statistician at the Centre interdisciplinaire de recherche en réadaptation et intégration sociale.
The introduction of this thesis is on the DCQ and its usefulness in the early detection of atypical dementia. This section also covers the literature surrounding the cognitive differences that exist between monolingual and bilingual older adults on tests such as the DCQ. Chapter 1 of this thesis is an article of which I am the primary author. This article will be submitted for publication during the fall of 2020. All researchers and clinicians who either participated in designing the DCQ, helped with participant recruitment or with testing, have also been included as co-authors for this article. Lastly, the conclusion of this master’s thesis includes a broader interpretation the study’s results and contains several final remarks.
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Introduction
With an increasingly aging population, the World Health Organization (2019) has estimated that worldwide, 50 million people currently live with a Major neurocognitive disorder, which is more commonly known as “dementia”. As there are nearly 10 million new cases every year, the total number of people with dementia is projected to reach 82 million in 2030 (World Health Organization, 2019). With this increasing prevalence, the annual cost of dementia in Canada alone has been estimated at 10.4 billion dollars. With 76,000 new cases of dementia diagnosed every year, this cost is expected to rise above 16.6 billion dollars by the end of 2030 (Public Health Agency of Canada, 2014). This significant rise has been linked to older adults losing their independence and relying on others to live safely, burdening their family members and the health care system in the process (Antoniou & Wright, 2017).
As a result, one of the great challenges facing our society today is preserving healthy brain function in our aging population. This is essential so that aging individuals may continue to keep their independence in their daily lives and for as long as possible. To this end, the timely detection of cognitive issues is increasingly important so that patients may be given access to earlier interventions and management, with the aim of preserving their cognitive abilities. To do this, multiple cognitive screening tools are currently and widely used in clinical settings. These tools include the Mini-Mental State Examination (MMSE; Folstein, Folstein & McHugh, 1975), the Montreal Cognitive Assessment (MoCA; Nasreddine, Charbonneau, & Cummings, 2005), and the Addenbrooke Cognitive Assessment (ACE; Mathuranath, Nestor, Berrios, Rakowicz, & Hodges, 2000), or its revised version (ACE-R; Mioshi, Dawson, Mitchell, And, & Hodges, 2006). Often used as screening tests for cognitive impairments, these tools aid clinicians in early detection of cognitive
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changes, the first step toward an accurate diagnosis of potential early onset of dementia. They also hold a key importance in providing an explanation to patients and families regarding recent changes in their function, mood, and behaviour.
Although these tools have shown to be effective in primary health care in identifying early cognitive impairments, it is important to note that several shortcomings have been reported with their use. Firstly, the existing tools which measure cognitive aspects surrounding typical dementias (e.g., Alzheimer's disease in its amnesic variant or vascular cognitive disorder), lack in the proper measurement of the atypical types (e.g., language, visual or frontal/dysexecutive variants of Alzheimer's disease, progressive primary aphasia, and the spectrum of frontotemporal dementia). As a result, the delay between the onset of symptoms and the diagnosis of atypical dementias can reach up to five years. This significantly delays management and treatment and increases the burden on the health care system (Gorno-Tempini, 2011; McKhann et al., 2011; Rascovsky et al., 2011).
Secondly, the tools currently used in our primary health care for cognitive screenings under-diagnose cognitive issues as many are not adapted to the updated criteria of cognitive disorders and dementia. In fact, in 2011, the National Institute on Aging–Alzheimer’s Association (NIA-AA) addressed several limitations regarding the diagnosis of Alzheimer’s disease (AD) by updating the diagnostic criteria. They introduced the concept that AD progresses over time and is manifested across a continuum. This reconceptualization acknowledges that individuals gradually progress from the preclinical stage of AD to mild cognitive impairment, and finally to dementia (Reiman et al., 2011). Consequently, with this new knowledge and to properly assess memory, it is believed that cognitive screening tests should include recall tasks with substantial delays of 10-30 minutes in order to increase the level of difficulty. Indeed, this would give patients more time to forget the items to recall if
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they were going to do so, thereby measuring a cardinal symptom present very early on in the development of AD (Reiman et al., 2011). Unfortunately, as most cognitive screening tools are administered within 10 minutes, these longer recall task delays are not always possible. Moreover, as AD has been redefined as a spectrum of different clinical phenotypes (amnesia, visual, language and frontal-dysexecutive functioning) in 2011, many cognitive screening tasks do not currently cover all of these domains when testing and evaluating patients. In other words, most major cognitive screening tests currently available have failed to keep pace with these clinical and nosological changes (Laforce et al., 2018).
Thirdly, most of the current tools available have not yet incorporated a behavioural scale to screen for changes in behaviour. Nonetheless, dementia, or to a certain extent earlier stages of cognitive impairment, may first affect speech and memory but they also have a large impact on judgment and behaviour. To measure these changes, the patient or their family members and professional carers should be consulted regarding the patient’s daily behaviours and changes that might be occurring. These behavioural changes can usually be examined through a structured or unstructured interview assessing judgment, which is first given to the patient. Follow-up questions regarding behaviour can then be administered and reported by a significant other or a caregiver (Sheehan, 2012).
In response to the absence of suitable screening tools designed for atypical dementias with updated dementia criteria incorporated into their means of testing, the Dépistage Cognitif de Québec (DCQ; www.dcqtest.org) was developed by Laforce et al., (2018). This new cognitive screening tool includes a behavioural symptom screening index exploring: depression, anxiety, delusions, hallucinations, irritability and aggression, apathy, disinhibition and impaired judgment, perseveration and compulsions, loss of empathy/sympathy and self-criticism. Designed specifically for atypical dementias at
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the Clinique Interdisciplinaire de Mémoire (CIME), of the Centre Hospitalier Universitaire de Québec, the DCQ was created by a team of professionals from different fields (behavioural neurologists, neuropsychiatrists, geriatricians, geriatric psychiatrists, clinical neuropsychologists and a speech-language pathologist). Precisely, it tests patients on five relevant cognitive domains: memory, visuospatial abilities, executive functions, language and behaviour (Laforce et al., 2018). It was constructed based upon updated diagnostic criteria for atypical dementias such as variant AD (McKhann et al., 2011), Primary progressive aphasias (PPA; Gorno-Tempini, 2011), and the Frontotemporal lobar degeneration spectrum (FTLD; Rascovsky et al., 2011).
Recently validated among a population-based sample of 410 healthy French-speaking Canadian adults, the DCQ showed a strong validity with existing cognitive screening tests by highly correlating with the MoCA (Cronbach’s alpha value of .74) and even showing superiority over the MoCA in detecting atypical dementias (Laforce et al., 2018; Sellami et al., 2018). The DCQ has also demonstrated appropriate internal consistency, an adequate test-retest reliability and excellent interrater reliability. Furthermore, its psychometric properties have been found to be equivalent to those of other tests considered as gold standard in cognitive screening, yet it also addresses their limitations. With this new instrument, Laforce et al., (2018) have thus provided clinicians with a more advanced test allowing a more focused screening of various cognitive domains for patients presenting symptoms of typical and atypical dementias. By using the DCQ in clinical settings, it is believed that neuropsychologists will be able to reduce missed or delayed identification of atypical dementia and accelerate therapeutic intervention.
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The English Validation of the DCQ in Linguistically Diverse Anglophones
Due to its excellent psychometric properties and for its future use all over North America, the DCQ has recently been translated into English and is currently being validated in this second language (Meilleur-Durand et al., in preparation). As the acquisition of normative data for the validation of the DCQ is currently underway for its English translation in an older population-based sample, which is becoming both more culturally and linguistically diverse, it is essential for this new tool to take into account the various linguistic backgrounds of its anglophone participants. In fact, clinical neuropsychologists are nowadays increasingly more likely to encounter patients who speak more than one language as more than 50% of the world’s population is bilingual (Grosjean, 1982). As a result, authors like Mindt et al., (2019) have emphasized the need for neuropsychologists to engage in empirically supported, culturally responsive neuropsychological evaluation of linguistically diverse and underrepresented older populations. In other words, this implies that during the validation of new cognitive screening tools like the DCQ, neuropsychologists should not only obtain normative data for monolingual English speakers but also for linguistically different populations such as bilingual English speakers. By monolingual English speakers, we hereby designate individuals who have English as their first language and who have no second language knowledge. As for bilingual English speakers, we are referencing individuals who have English as their first language but are also highly proficient in any second language.
In fact, it is crucial to gather normative data for both linguistic groups as factors such as bilingualism may play a role in patient self-report, informant report, and expression of neuropsychiatric symptoms (Mindt et al., 2019) during psychometric evaluations. Without the proper specifications to guide the evaluations of bilingual populations, test results can be
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prone to misinterpretations that may lead to inaccurate diagnoses once instruments are validated and used in clinical settings (Léon, 2017).
Unfortunately, the preliminary psychometric testing of a new instrument in both monolingual and bilingual populations is rarely conducted in the current literature. Nevertheless, authors like Sousa and Rojjanasrirat (2011) have recommended that when a bilingual population is accessible, the new instrument should be pre-field-tested among bilingual individuals (preferably fluent in both the language of the original instrument and in the language the instrument was translated into). Ideally and most importantly, the bilingual sample should be extracted from the target population in which the instrument will be used. The APA Ethical Standard 9.02 (American Psychological Association, 2002) further emphasizes this by stating that psychologists are to “use assessment instruments whose validity and reliability have been established for use with members of the population tested.”
While the resources available for examining culturally diverse older adults have significantly improved over the past several years, only one cognitive screening test has been specifically standardized and validated for use in linguistically diverse adults (of which we are aware). This was done in Milman, Faroqi-Shah, Corcoran, & Damele's (2018) study on the MMSE, where the findings suggested that community dwelling highly proficient bilingual speakers may perform differently than monolingual speakers on raw and demographically adjusted MMSE. In fact, their bilingual groups had significantly lower scores than their matched monolingual groups and were more likely to be classified in the borderline/impaired range. Their results are also consistent with a growing body of research indicating that the MMSE scores and other cognitive screening tests scores, adjusted solely based on age and education are not enough. Notably, they do not fully correct for performance differences across diverse linguistic and ethnic groups. This further highlights
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the clinical importance of identifying and characterizing linguistic and cultural diversity, even when assessing highly educated and proficient healthy bilingual speakers.
The Importance of Normative Data for Both Monolingual and Bilinguals
Another benefit to preliminary psychometric testing of a new instrument in bilinguals lies within the possible cognitive differences that might exist between monolingual and bilingual populations. In fact, past studies have suggested that bilingual individuals could have several cognitive advantages over their monolingual counterparts. More precisely, bilinguals could have a larger "cognitive reserve", which is when the brain actively or eventually attempts to cope with damage (trauma, pathologies, aging, etc.) by using pre-existing cognitive processing approaches or by enlisting compensatory approaches (Stern, 2002, 2009, 2012). The concept of "cognitive reserve" could explain why the same amount of brain damage or pathology will have different effects on different individuals, even when brain size is similar. A combination of lifetime factors, experiences and exposures are the most commonly used proxies to measure cognitive reserve and have been summarized in various articles like that of Duncan and Phillips' (2016). These factors include higher IQ, late life recreational activity (Brewster et al., 2014), higher levels of education (Bennett, Schneider, Wilson, Bienias, & Arnold, 2005), cognitively stimulating activities (Wilson et al., 2013), and social engagement (Engelhardt, Buber, Skirbekk, & Prskawetz, 2010). Naturally, second language knowledge is also thought to be great for building cognitive reserve and to enhance cognitive functions among healthy older individuals (Klimova, 2018). Speaking more than one language may be similar to other mentally stimulating activities (Duncan & Phillips, 2016) and could not only be a contributor to cognitive reserve in bilinguals, but it could also protect against age-related decline.
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Furthermore, past studies have shown that language learning engages an individual in extensive brain networking, which has also been found to overlap with brain regions negatively affected by the aging process (Antoniou & Wright, 2017). As a result, bilingualism could act as a protective factor in preserving healthy brain function, as well as play a crucial role in delaying the incidence of dementia by four years (Bialystok, Craik, & Freedman, 2007). These substantial cognitive differences between monolingual and bilingual individuals can pose a challenge to neuropsychologists assessing cognitive functioning in bilingual populations compared to monolingual ones. As we will discuss, past literature has demonstrated that there might exist significant differences between these two populations regarding their performance on tests measuring memory, executive functioning as well as language, which are all cognitive abilities tested by the DCQ. As a result, monolingual or bilingual older adults may perform differently when assessed on cognitive screening tests like the DCQ, making it even more important to conduct preliminary psychometric testing in both groups. Awareness of the literature surrounding linguistic and cognitive differences between monolingual and bilingual healthy older adults will aid in interpreting their neuropsychological test performance, especially given the lack of normative data for these two different populations on current screening tests.
A Bilingual Advantage on Cognitive Tests in Healthy Older Adults
Firstly, several past studies have shown a bilingual advantage on episodic memory tasks in comparison to their monolingual counterparts. A longitudinal study by Ljungberg, Hansson, Andrés, Josefsson, and Nilsson (2013) investigated bilingual advantages on episodic memory recall during the trajectory of life and showed that bilinguals outperformed monolingual participants at baseline and across time on three different recall tasks. Similar
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results were also found by Schroeder and Marian (2012), where bilingual and monolingual older adults were compared on a picture scene recall task that also assessed episodic memory.
They found that bilinguals recalled significantly more items overall, thus exhibiting a better episodic memory than their monolingual peers.
This episodic memory, which can be referred to as a neurocognitive system that enables human beings to remember past experiences, is subject to decline with healthy aging (Tulving, 2002). The decline in episodic memory has also been attributed to less successful executive functioning by hindering older adults’ ability to implement controlled encoding and retrieval processes. Executive functioning is another cognitive domain that has been found to differ between bilingual and monolingual individuals. For example, Schroeder and Marian (2012) administered a very well-known test measuring executive functioning called the Simon task to their bilingual and monolingual older participants. They found that bilinguals demonstrated higher executive functioning on this task compared to monolingual participants. Similar results on the Simon task were also found in studies like Cox et al., (2016) as well as Bialystok, Craik, and Luk (2008).
Furthermore, in a study by Bialystok, Klein, Craik, and Viswanathan (2004), the authors aimed to determine whether the bilingual advantage for executive functioning persisted in older adults and whether bilingualism attenuated the negative effects of aging on cognitive control in this population. To do this, they conducted two different studies with older adults during which monolinguals and bilinguals were compared on background experiences and on their performance on the simple and complex Simon task. In all studies, bilingualism was associated with smaller Simon task effect costs for both age groups, and to faster response times in conditions that placed greater demands on working memory. These findings were partly replicated in Salvatierra and Rosselli's (2011) study where it was
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observed that older bilinguals were more efficient at inhibiting irrelevant information than older monolinguals but only under the simple Simon task condition. Nevertheless, in all cases, a bilingual advantage was found to be greater in older participants, demonstrating that controlled processing can be carried out more effectively by bilinguals and suggesting that a second language knowledge helps to offset age-related losses in specific executive processes.
Apart from the widely known and used Simon task, other studies like Bialystok et al., (2008) as well as Incera and McLennan (2018) have used the Stroop task to demonstrate that older bilinguals outperformed their monolingual counterparts in tests measuring executive function. The Stroop assesses the ability to inhibit cognitive interference that occurs when the processing of a specific stimulus feature impedes the simultaneous processing of a second stimulus (Scarpina & Tagini, 2017). This process is also known as the Stroop effect and is a demonstration of cognitive interference where a delay in the reaction time of a task occurs due to a mismatch in stimuli. From this, Incera and McLennan (2018) found that the Stroop effect was reduced with higher levels of bilingualism and equivalent across all ages. Lastly, the Eriksen Flanker test, measuring executive control, has also been used to investigate the performance of aging bilinguals and monolinguals. The task is composed of a set of response inhibition tests used to assess the ability to suppress responses that are inappropriate in a particular context (Eriksen & Eriksen, 1974). The target is flanked by non-target stimuli which correspond either to the same directional response as the target (congruent flankers) or to the opposite response (incongruent flankers). Again, for both congruent and incongruent trials, bilinguals were found to outperform monolinguals (Abutalebi et al., 2015).
As tests assessing verbal fluency used during neuropsychological testing with retrieval efficiency place great demands on memory and executive control functions, bilinguals have also been shown to have an advantage over their monolingual counterparts
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for letter and category fluency tasks. In letter fluency tasks, participants are given a phonemic category (usually F, A or S) and are asked to enumerate as many words that start with a specific letter for one minute. Friesen, Luo, Luk, and Bialystok's (2016) examined potential bilingual advantages on letter fluency with four age groups: 7-year-olds, 10-year-olds, young adults, and older adults. They found that verbal fluency performance improved with age but more importantly, that beginning at 10 years of age, the executive control required for letter fluency was less effortful for bilingual than monolingual individuals, with a robust bilingual advantage emerging in adulthood. This bilingual advantage on letter fluency tasks was also found in Ljungberg et al., study (2013) and in Salvatierra and Rosselli (2011). As for the category fluency task, participants are asked to enumerate as many words that fit into a specific category for one minute. The categories used are often that of animals and/or fruits. In an paper by Obler, Martin, & Lozowick (1986), they found that their bilingual participants named significantly more animals than their monolingual counterparts on this type of language task.
Together, the studies discussed above seem to clearly suggest a bilingual advantage for specific memory, executive function, and language tasks. Nevertheless, it is important to mention that previous research has not always been systematic in assessing the effects of monolingualism and bilingualism in older adults. In fact, some authors like Mukadama, Andrew, and Livingston (2017), argue against a bilingual advantage that would protect from cognitive decline or dementia. In their recent meta-analysis examining the strength of the protective effect of bilingualism on dementia in both retrospective and prospective studies, they found that bilingualism did not protect from cognitive decline, as only retrospective studies showed positive effects of bilingualism. Unfortunately, these types of studies are more prone to confounding variables such as education, or cultural differences in presentation
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of dementia and are consequently not suited to establishing causative links between risk factors and outcomes. In comparison, prospective studies are less susceptible to extraneous variables but did not show that bilingualism protects from dementia. Moreover, some studies have not been able to replicate the previous findings mentioned and have found no group advantage on memory tasks, executive functioning and language fluency.
No Cognitive Advantage between Monolingual and Bilingual Older Adults
In Bialystok, Craik, and Luk's study (2008), no differences were found between older monolingual and bilingual participants on the forward and backward Corsi blocks tasks and the Self-ordered pointing task, both measuring working memory. In the first task, the subject is asked to observe the sequence of blocks "tapped,” and then repeat the sequence back in order or in reverse (Kessels, van Zandvoort, Postma, Kappelle, & de Haan, 2000). The task starts with a small number of blocks and gradually increases in length up to nine blocks. The test measures both the number of correct sequences and the longest sequence remembered. In the second task, participants are presented with an examination booklet. On each page the same set of items is shown; however, the location of each item varies randomly from page to page. Participants are instructed to point to a different item (e.g., abstract design) on each page without pointing to one they have touched previously (Ross, Hanouskova, Giarla, Calhoun, & Tucker, 2007). Similarly, in another study using the latter task to measure working memory, 90 male participants (26 bilingual and 64 monolingual), underwent an intelligence test at age 11 years and were assessed on a wide range of executive and social cognition tasks at age 74. Effects of bilingualism on the Self-ordered pointing task measuring working memory was once again nonsignificant in older adults (Cox et al., 2016).
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For tasks measuring executive functioning, some researchers have also found no group advantage. For example, Kousaie and Phillips (2012) who administered the Stroop task to older monolingual and bilingual participants found no effect or advantage of bilingualism. This was also the case in Kousaie, Sheppard, Lemieux, Monetta, and Taler (2014) where they administered the Stroop and the Simon task. In another study by Clare et al., (2016), they examined the performance of older Welsh/English bilinguals and English monolingual speakers on a range of tasks assessing aspects of executive control. These included the Stroop and the Simon task, which were used to determine whether there was evidence for a bilingual advantage in executive processing. They found no overall advantage for either group. The absence of a group advantage was also found in Obler et al., (1986), where they administered the letter fluency task, as well as a backward month naming task. With this lack of evidence of a bilingual advantage on executive functioning, one can doubt the robustness and the specificity of the previous findings mentioned.
As tasks measuring letter fluency have been strongly linked to executive function, authors like Rosselli et al., (2000) have also found no group advantage when comparing the performance of three groups (anglophone monolingual, Spanish monolingual, and Spanish-English bilinguals) on the letter fluency task. When administering specific language-related tasks measuring lexical access, like that of the Cookie Theft Task (oral picture description), the Boston Naming Task (word naming task), a Sentence Repetition from the Multilingual Aphasia Examination (MAE) and a category fluency task, they also found no significant performance differences between the groups. This absence of a group advantage on the Boston Naming Task, as well as on a sentence comprehension task can also be found in Obler et al., (1986). Overall, this suggested that perhaps bilingualism does not actually influence performance on free spontaneous fluency tasks, nor on word naming, repetition tasks, and
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during the generation of words by phonemic categories. This absence of a bilingual or a monolingual advantage on categorical fluency tasks has also been replicated in Ljungberg et al.'s (2013) longitudinal study, as well as in Friesen, Luo, Luk, and Bialystok's (2016) article.
A recent meta-analysis by Lehtonen et al. (2018), also examined the differences found between bilingual and monolingual adults on six executive domains, using 891 effect sizes from 152 different studies. The domains studied were those of working memory, inhibitory control, attention shifting, as well as verbal and category fluency. No systematic evidence of a bilingual advantage in adults was found in any of these domains after correcting for observed publication bias, apart from the verbal fluency tasks. In fact, they found a small bilingual disadvantage for language-related tasks and thus concluded that the available evidence did not provide systematic support for the widely held notion that bilingualism is associated with benefits in cognitive abilities in older adults.
A Monolingual Advantage on Cognitive Tests in Older Adults
This monolingual advantage found in Lehtonen's (2018) meta-analysis, has also been observed in other scientific work which studied memory, executive functions and language in bilinguals vs. monolinguals. More precisely, authors like Fernandes, Craik, Bialystok, and Kreuger (2007) found a monolingual advantage for semantic memory tasks. They examined free recall performance in younger as well as older monolingual and bilingual adults and found that older age and bilingualism were associated with lower recall scores. Other researchers like Clare et al., (2016) found that when assessing working memory in older monolingual and bilinguals on a spatial span forward test (resembling the Corsi Block test), a significant advantage for monolinguals was present. Similar results were found in Obler et al., (1986) where they used the Rey–Osterrieth complex figure. In this task, participants were
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asked to reproduce a complicated line drawing, first by copying it freehand (recognition), and then by drawing it from memory (recall). Additionally, a monolingual advantage has also been found in tasks specifically measuring executive functions. In fact, Clare et al., (2016) found that monolinguals performed significantly better on the Delis-Kaplan Executive Function System (D-KEFS) Design Fluency switching tests, measuring set-shifting and switching, as well as on the D-KEFS’s letter fluency Task.
These inconsistencies found in the current literature also apply to lexical retrieval tests, as Clare et al., (2016) found that monolinguals were superior to bilinguals on English language tasks. Monolinguals achieved significantly higher scores on a lexical decision task such as the D-KEFS’s category fluency task, the Boston Naming Task, a Spot-the-Word test and the British Picture Vocabulary Scale (a receptive assessment of vocabulary). These significant differences between groups on vocabulary and picture naming yielded medium to large effect sizes. Similarly, these findings were also found in a study by Bialystok et al., (2008) where they concluded that monolinguals were better on tasks measuring lexical retrieval compared to bilinguals. Precisely, a monolingual advantage was found for fluency tests in which monolinguals generated more items than bilinguals, for both letter, and category conditions. Furthermore, in the Boston Naming Task, their monolinguals outperformed their bilinguals in both the picture, and the definition version of the test.
Inconsistencies
Researchers do not seem to agree on the existence of a bilingual or a monolingual advantage on specific cognitive tests in older adults. Recent research is contradictory as a large proportion of studies has found a significant advantage of bilingualism on cognitive abilities in aging, while a comparable proportion has not found any existing significant
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differences between groups. A third, and a slightly less abundant group of authors has even found a positive effect for monolinguals (see Table 1 for a complete summary of the studies discussed). It is thus important to take note of these discrepancies and to conduct preliminary psychometric testing of both monolingual and bilingual participants when using new cognitive screening tests like the DCQ. It is even more crucial to conduct a preliminary testing of this new tool in different linguistic populations as the DCQ uses similar cognitive tests to those employed in the current literature. In fact, the memory index of the DCQ includes a recall and a recognition task; the executive index has a backward/forward digit span, a naming the months backwards, a modified version of the Stroop, as well as a letter fluency task; and lastly, the Language Index contains fluency, naming, writing, word finding and repetition tasks.
When it comes to the inconsistencies found in the literature, it is reasonable to say that sufficiently large group sizes, methodological rigour, well designed and thoroughly analyzed studies can be found on all sides of the debate (Bak & Robertson, 2017). This makes it even more difficult to attribute more credibility to one school of thought than to another. Nonetheless, there are numerous potential reasons for these inconsistent findings but, since most studies which have reported definite advantages for one group or the other have not always been replicated, this leads to concerns of publication bias, statistical flaws, and failure to match groups on potentially confounding variables (Lehtonen et al., 2018).
A further explanation as to why past studies have not been able to come to a consensus lies within the definition of “bilingualism.” In fact, as bilingual language skills vary widely according to the age of acquisition, exposure and immersion, there is no current standard operational definition of bilingualism and how it should be measured. When comparing monolinguals to bilinguals, many researchers do not properly explain how they classify their
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participants into one group or the other. Various articles have included very low proficient bilingual individuals into their monolingual groups, while others have chosen to only include individualswithout any previous knowledge of a second language.
Additionally, for the bilingual group, some authors have only included individuals who have balanced bilingualism (equally proficient in each language they speak) into their bilingual group, while others are more permissive and also include unbalanced bilinguals (individuals who speak two languages but are more skilled in one language than in the other; Léon, 2017). In terms of measuring bilingualism, some studies have classified participants as highly bilingual based solely on self-reported measures of proficiency, while other have preferred to measure bilingual proficiency more thoroughly, asking participants to complete a self-rating of proficiency, an oral language test as well as a naming and a definition test.
Lastly, many studies, contrary to the recommendations made by Mindt and colleagues (2019), compare monolingual and bilingual groups that have different first languages. As a result, many studies do not test their bilingual groups in their strongest/primary language which may create a bias. In fact, individuals should typically be tested in their most proficient (e.g., strongest or primary) language whenever possible and appropriate, as bilingual older adults with mild cognitive impairment generally experience loss of their second language before the loss of their first language (Mindt et al., 2019). Consequently, it is important to assess the patient in the appropriate and strongest language in order to ensure the most accurate results.
Considering the inconsistencies existing in the current literature is necessary to better compare cognitive functions between healthy older monolingual and bilingual adults when validating new cognitive screening tests like the DCQ. To this end, comparisons between demographically balanced groups, divided using a clear and consistent method to assess
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bilingualism, is necessary for future studies. Unfortunately, as no concrete measuring tools exist to determine an individual’s bilingual status, especially with self-reporting measures, it is important that researchers regard bilingual status as a continuous variable (Burkert, 2016). As have stated Luk and Bialystok (2013), bilingualism should not be measured as a categorical variable because the criteria that determine an individual’s designation as monolingual or bilingual are fuzzy at best. In fact, if one were to count individuals as only being bilingual when they are completely and perfectly fluent in each of their languages, they would be left with no label for most people who use two or more languages regularly, but who do not have native-like fluency in each (Grosjean, 1994).
Not only should bilingualism be regarded as a continuous variable, but recent studies have shown that it should also be studied through all its forms to better represent most bilingual populations. In fact, increased diversity in bilingualism and how it is used across social contexts, may be related to better behavioural cognitive performance (Pot, Keijzer, and de Bot, 2018). Interestingly, effects of bilingualism do not depend on age of acquisition. More generally, purely knowing different languages does not relate to enhanced performance, but it is rather the use of these different languages that may show small positive effects on cognition.
Objectives of the Current Study
Considering the limitations outlined above in studies exploring cognitive differences between heathy older adults with differences in language knowledge, and also considering the discrepancies between results in the literature, the current study aimed to compare older monolingual and bilingual anglophones on the English version the DCQ, in a sample of healthy English-speaking Canadians aged 50 years and over. This sample was representative
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of the DCQ’s targeted population in a clinical setting. The main objective was to compare the groups on their total DCQ scores and their five-index scores (Memory, Visuo-spatial, Executive, Language and Behaviour) to study the possible differences that lie between groups. We further aimed to suggest adaptations or considerations for the future clinical use of the English DCQ.
As no consensus can be found regarding potential differences between monolinguals and bilinguals on cognitive tasks involving memory, executive functions and language, the present research is an exploratory study and has a nondirectional alternative hypothesis. In addition, since the differences that might exist between monolinguals and bilinguals on other types of cognitive tasks involving visuospatial functioning and behaviour have yet to be studied, this adds an observational dimension to the research design. In fact, visuospatial function and behaviour are two important cognitive domains that might have substantial effect on neuropsychological assessment results, diagnoses, and treatment recommendations, making them important abilities to be studied when comparing monolingual and bilingual groups.
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Chapter 1: Article
Cognitive Differences Between Healthy Monolingual and Bilingual Anglophones on the English Version of the Dépistage Cognitif de Québec (DCQ): A New Screening Tool for
Atypical Dementia
Marianne Lévesquea,b,c, Marie-Christine Ouelleta,b. Synthia Meilleur-Durandc, Brandy Callahan e, David Bergeronc, Ging-Yuek Hsiung f, Louis Verretc, Marie-Pierre Fortinc, Mario Masellisg, Pamela Jarrett h, Serge Gauthier i, Stéphane Poulinc, Stephen Cunnane j, Sylvia Villeneuve k, Joël Macoird, Rémi W. Bouchardc & Robert Jr. Laforcea,c.
a School of Psychology, Laval University, Quebec, Canada, b Center for Interdisciplinary Research in Rehabilitation and Social Integration, Quebec, Canada, c Clinique
Interdisciplinaire de Mémoire (CIME), CHU de Québec, Canada, d Département de Réadaptation, CERVO Brain Research Centre, Faculté de médecine, Université Laval, Québec, QC, Canada, e University of Calgary and University of Calgary & Hotchkiss Brain Institute, Calgary, AB, Canada, f Vancouver Coastal Health Research Institute, Vancouver, BC, Canada, g Sunnybrook Research Institute, Toronto, ON, Canada, h Horizon Health Network, Saint John, NB, Canada, i McGill University Research Centre for Studies in Aging, Montreal, QC, Canada,j Research Center on Aging, Sherbrooke, QC, Canada, k
Douglas Mental Health Institute, Montreal, QC, Canada
Corresponding author:
Robert Jr. Laforce M.D., Ph.D.
Neurologue et Neuropsychologue Professeur Agrégé de Neurologie Faculté de Médecine, Université Laval Clinique Interdisciplinaire de Mémoire
Département des Sciences Neurologiques CHU de Québec
1401, 18ième rue, Québec, Canada G1J 1Z4 Tel.: 418-649-5980
Fax: 418-649-5981
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1.1 Résumé
Alors que les capacités cognitives peuvent différer entre individus monolingues et bilingues, il est primordial de prendre en compte ces différences lors de l’administration de dépistages cognitifs. Dans le cas contraire, les évaluations pourraient faire l’objet d’une mauvaise interprétation, pouvant entraîner des diagnostics erronés. L’objectif de cette étude était de comparer des personnes âgées en bonne santé anglophones monolingues et bilingues sur la version anglaise d’un nouveau test de dépistage cognitif conçu pour une meilleure reconnaissance des démences atypiques : le Dépistage Cognitif de Québec (DCQ,
www.dcqtest.org). Le DCQ a été administré à 85 participants anglophones de 50 ans et plus à différents endroits au Canada. Le Montreal Cognitive Assessment (MoCA) a permis de déterminer l’éligibilité des participants et leurs compétences linguistiques ont été déterminé par le Language Experience and Proficiency Questionnaire (LEAP-Q). Parmi les participants, 30 monolingues et 29 bilingues remplissaient les critères d’inclusion. Les groupes étaient équivalents en âge, en années de scolarité et sur leurs scores au MoCA. Les groupes ont été comparés sur leurs scores totaux au DCQ et sur les cinq index de l’outil : mémoire, visuospatial, exécutif, langage et comportement. Les analyses ont montré un avantage statistiquement significatif pour les bilingues sur l’index du langage. Cet effet a également contribué à l’avantage bilingue sur les scores totaux du DCQ. Suite à une correction Bonferroni, les différences entre les groupes n’ont pas été maintenues. Aucune différence significative n’a été constatée sur les autres index. Cette étude est la première à explorer les propriétés psychométriques du DCQ chez les monolingues et bilingues plus âgés et testés dans leur langue maternelle. Les résultats soulignent l’importance d’identifier et caractériser la diversité linguistique avant d’utiliser des outils de dépistage en milieu clinique.
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Les avantages cognitifs du bilinguisme devraient être considérés lors de l’interprétation des résultats et discutés dans les rapports neuropsychologiques.
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1.2 Abstract
Cognitive abilities between monolingual and bilingual individuals may differ, making it important to factor in this issue during the administration of cognitive screening tools. Otherwise assessments could be subject to misinterpretation, leading to inaccurate diagnoses. The current project aimed to compare healthy older monolingual and bilingual anglophones on the English version of a new cognitive screening test designed for better recognition of atypical dementia: the Dépistage Cognitif de Québec (DCQ, www.dcqtest.org). The DCQ was administered by qualified psychometricians to 85 native English-speaking participants aged 50 years and over, in various sites across Canada. The Montreal Cognitive Assessment (MoCA) was used to determine participants’ eligibility. Language proficiency was established using the Language Experience and Proficiency Questionnaire (LEAP-Q). Amidst the anglophone participants recruited, 30 monolingual anglophones and 29 bilingual anglophones met inclusion criteria. Groups had similar age, education and MoCA scores. Monolinguals and bilinguals were compared on their total DCQ scores and each of the five DCQ indexes: Memory, Visuospatial, Executive, Language and Behavioural. Statistical analyses showed a significant advantage for the bilingual participants on the Language Index, which also contributed to the significant bilingual advantage for the overall DCQ scores. When applying a Bonferroni correction, the differences between groups were however not maintained. No significant differences were found on any of the other indexes. This study is the first to explore psychometric properties of the DCQ in older monolingual and bilingual participants tested in their native language. Results highlight the importance of identifying and characterizing linguistic diversity before using new screening tools in clinical settings. The potential cognitive advantages of bilingualism should be considered when interpreting test data and explicitly discussed in neuropsychological reports.
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Introduction
With an increasingly aging population, the World Health Organization (2019) has estimated that worldwide, 50 million people currently live with a Major neurocognitive disorder, which is more commonly known as “dementia”. These include typical dementias (e.g., Alzheimer's disease in its amnesic variant or vascular cognitive disorder), as well as the atypical variants (e.g., language, visual or frontal/dysexecutive variants of Alzheimer's disease, progressive primary aphasia, and the spectrum of frontotemporal dementia). As the number of new cases is expected to increase by nearly 10 million every year, it is expected that by the year 2030, the number of individuals living with dementia will reach 82 million (World Health Organization, 2019). One of the great challenges facing our society today is preserving healthy brain function in our aging population. To this end, the timely detection of cognitive issues which may lead to dementia is crucial so that patients may be given access to earlier interventions and management of their cognitive impairments.
To detect early signs of typical dementia, multiple cognitive screening tools are currently and widely used in clinical settings. These tools include the Mini-Mental State Examination (MMSE; Folstein, Folstein & McHugh, 1975), the Montreal Cognitive Assessment (MoCA; Nasreddine, Charbonneau, & Cummings, 2005) and the Addenbrooke Cognitive Assessment (ACE; Mathuranath, Nestor, Berrios, Rakowicz, & Hodges, 2000). Unfortunately, these tools have been shown to lack in the proper specificity to screen for atypical dementias. As a result, the Dépistage Cognitif de Québec (DCQ; www.dcqtest.org), was recently developed in French by Laforce et al., (2018) at the Clinique Interdisciplinaire de Mémoire (CIME) of the Centre Hospitalier Universitaire de Québec and was designed precisely for atypical dementias. It tests patients on five relevant domains: memory, visuospatial abilities, executive functions, language and behaviour (Laforce et al., 2018). Due
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to its superiority over the MoCA in detecting atypical dementias (Sellami et al., 2018), its adequate internal consistency, test-retest reliability, as well as its excellent interrater reliability (Laforce et al., 2018), the DCQ has recently been translated into English. Its validation in this second language is currently underway among an older population-based sample (Meilleur-Durand et al., in preparation) so that it may be used by neuropsychologists all over North America.
As older individuals are becoming both more culturally and linguistically diverse with increases in immigration, it is essential for the validation of this new tool in English to include the various linguistic backgrounds of its future anglophone sample. In fact, authors like Mindt et al., (2019) have emphasized the need for neuropsychologists to engage in empirically supported, culturally responsive neuropsychological evaluation of linguistically diverse and underrepresented older populations. Considering that in Canada only, the English–French bilingualism rate in 2016 reached its highest proportion ever at 17.9% (Statistics Canada, 2017), authors like Sousa and Rojjanasrirat (2011) have also recommended that when a bilingual population is accessible, new instruments should be pre-field-tested among monolingual but also bilingual individuals.
The pre-field testing of new cognitive screening tests among linguistically diverse older individuals is also crucial as factors such as bilingualism may play a role in patient self-report, informant self-report, and expression of neuropsychiatric symptoms (Mindt et al., 2019) during psychometric evaluations. Without the proper specifications to guide the evaluations of bilingual populations, test results can be prone to misinterpretations that may lead to inaccurate diagnoses once instruments are validated and used in clinical settings (Léon, 2017). Additionally, preliminary psychometric testing of instruments like the DCQ in both monolingual and bilingual populations is essential as the current literature indicates that
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cognitive differences may exist between these groups. In fact, some researchers have found significant differences between these two populations regarding their performance on tests measuring working and episodic memory, attention/executive functioning, particularly cognitive control, as well as on verbal measures such as expressive vocabulary, receptive vocabulary and verbal fluency. As these cognitive functions are all evaluated by the DCQ, with a forward and backward digit span, an immediate and delayed recall task, a recognition task, a letter fluency task, a modified version of the Stroop, a category fluency task, and a naming as well as a repetition task, it is even more important to consider possible cognitive differences between monolinguals and bilinguals on this tool. The importance is further emphasized by the fact that not all researchers have found the same results when comparing both groups on these various cognitive domains. In fact, a large proportion of authors claim that there exists a bilingual advantage in older adults on tasks measuring memory, executive functions, and language, while a comparable proportion asserts that no significant differences exist between groups. A third, but less abundant body of research, has also supported the presence of a monolingual advantage. A summary of recent literature on the subject can be found in Table 1.
Numerous potential reasons can explain the inconsistencies found in the current literature, which include concerns of publication bias, statistical flaws, and failure to match groups on potentially confounding variables (Lehtonen et al., 2018). Past studies have also not always agreed on how to define “bilingualism”, as bilingual language skills vary widely according to age of acquisition, exposure, and immersion. Apart from the absence of a standard operational definition of bilingualism, many researchers have not properly explained how they classified their participants into a monolingual or a bilingual group.
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Others, contrary to recommendation (Mindt et al., 2019), have often compared monolingual and bilingual groups that have different first languages.
Resolving the inconsistencies in the current literature by using demographically balanced groups, divided using a clear and consistent method to assess bilingualism, and tested in their primary language, is necessary to better compare cognitive functions between older monolingual and bilingual adults when validating new cognitive screening tests. Unfortunately, preliminary psychometric testing of new instruments in both these populations has rarely been conducted. To date, we are aware of only one cognitive screening test has been specifically standardized and validated for the use of linguistically diverse older adults. This was done with the MMSE, by Milman et al., (2018) in which their findings suggested that even neurologically healthy, highly proficient bilingual speakers performed differently than monolingual speakers and were more likely to be classified in the borderline/impaired range than matched monolingual individuals. These results further suggest that substantial differences may influence the psychometric evaluations of bilingual populations compared to monolingual ones, which poses a challenge to neuropsychologists. Having highlighted the need to conduct preliminary testing of new tools in diverse linguistic groups, the current study aimed to compare older monolingual and bilingual anglophones on the English version the DCQ, in a sample of healthy Canadians aged 50 years and over. This sample was representative of the DCQ’s targeted population in a clinical setting. The main objective of this exploratory study was to compare the groups on their total DCQ scores and on the DCQ’s five index scores (Memory, Visuo-spatial, Executive, Language and Behaviour). If significant differences were to be found between these two groups, adaptations and considerations for the future clinical use of the English DCQ were to be suggested.
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Methods
Participants
A total of 85 healthy native English-speaking Canadians aged between 53 and 80 years were recruited. This was done via public announcements, advertisements and through partnerships with other institutions (e.g.: the Clinique Interdisciplinaire de la Mémoire in Quebec City, the McGill Centre for Studies in Aging and the Douglas Hospital Research Center in Montreal, the Sunnybrooke Research Institute in Toronto, the Hotchkiss Brain Institute in Calgary, the St-Joseph Hospital in St. John and the University of British Columbia Hospital in Vancouver).
Participants were recruited if English was their first language and if they did not report a history of traumatic brain injury, delirium, brain surgery, neurological disease, encephalitis or meningitis, untreated metabolic condition, psychiatric illness, brain oncological therapy, alcohol/drug abuse, disabling visual/hearing disorders, experimental therapy, and illiteracy.
Materials
Montreal Cognitive Assessment (MoCA)
Global cognition was assessed using the MoCA(Nasreddine et al., 2005), a 12-minute cognitive screening tool to detect mild cognitive impairment. The MoCA is scored out of 30 points and assesses visuospatial and executive function, naming ability, memory, attention, language, abstraction, and orientation.
Language Experience and Proficiency Questionnaire (LEAP-Q)
To determine their linguistic profiles and to place them in either the monolingual or bilingual group for the current study, all participants completed the LEAP-Q (Marian,
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Blumenfeld, & Kaushanskaya, 2007). This questionnaire (see Appendix A) measures an individual’s level of bilingualism based on their self-reported second language proficiency for reading, writing and oral comprehension. The participants are asked to rate themselves with the help of a Likert scale from 0 (i.e., extremely low) to 10 (i.e., perfect, native level). Age of second language acquisition, current language dominance as well as current second language exposure are also information gathered by the questionnaire.
The internal and criterion-based validity of the LEAP-Q have been established (Marian et al., 2007), and have proven to be reliable indicators of language ability. The questionnaire has been translated into 16 other languages and is valid among a healthy adult population with high school levels of literacy. As bilingualism is a concept difficult to measure, the LEAP-Q aims to capture factors that have previously been identified as important contributors to bilingual status such as language competence (including proficiency, dominance and preference ratings across speaking, understanding, reading, and writing), age of language acquisition, modes of language acquisition, prior language exposure, and current language use.
Anglophones who reported no second language knowledge on the LEAP-Q were placed in the monolingual group. Those who self-reported a level of proficiency of 7 or more (good to perfect) on their speaking, understanding, and reading skills in their second language, and who also reported using two languages regularly, were placed in the bilingual group. All participants reporting scores lower than 7 were excluded for the purpose of the current study.
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The DCQ (Laforce et al., 2018; Sellami et al., 2018) is a cognitive screening test administered in an average time of 25 minutes. It is scored on 100 points and targets five relevant domains: Memory, Visuospatial, Executive, Language, and Behaviour (see Appendix B). The Memory Index (out of 24) assesses basic attention using the forward digit span, a short-term recall task of eight words with delayed recall after 15 minutes and a recognition task. The Visuospatial Index (out of 14) tests visual recognition of overlapping figures and spatial rotation (the subject is asked to recognize an image from a scene, representing his viewing angle, which is changed throughout the task). This index also includes a geometric figure drawing test. The Executive Functions Index (out of 10) includes a backward digit span, naming the months of the year backwards, an alternating graphic sequence test, a two-item verbal abstraction task, a phonemic fluency (of the letter A) and a modified Stroop test. The Language Index (out of 28) comprises a scene description task to assess spontaneous speech, a naming and single-word writing task, a multi-sentence writing test, assessment of comprehension through a sentence-picture matching test, a semantic verbal fluency task, and a task requiring the participant to repeat short as well as long and complex sentences. Finally, the Behavioural Index (out of 24) explores 10 domains (depression, anxiety, delusions, hallucinations, irritability and aggression, apathy, disinhibition and impaired judgment, perseverations and compulsions, loss of empathy/sympathy and self-criticism) as reported by a significant other.
Procedure
Participants were first contacted by phone. To make sure they were healthy, an initial screening was conducted to gather information on current and past medical history. Participants were then either assessed at one of our testing sites or visited in their homes by
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a trained research assistant. They were informed about the nature of the study and the types of tasks that would be administered. Informed written consent was obtained from all participants. Testing occurred in a single session lasting approximately one hour. Participants first completed the LEAP-Q to assess their linguistic profiles. The MoCA and the DCQ were then administered in a randomized order to account for any carryover effect between the tests. Lastly, to complete the DCQ’s caregiver questionnaire for the behavioural index, participants were asked to provide the phone number of a family member, friend, spouse or caregiver. These individuals were then contacted within the following 2 months of the testing session to complete a 5-minute interview over the phone. This study was approved by the Ethics Committee of Laval University, Québec City.
Statistical Analysis
Basic descriptive analyses included means and standard deviations. As Levene's test was significant (p < .05), suggesting a violation of the assumption of equal variances, groups were compared using Welch's unequal variances T-test. Monolinguals and bilinguals were compared on their education levels, age, MoCA total score, DCQ total score and for each DCQ index: Memory, Visuospatial, Executive Function, Language, and Behavioural. This was followed by a Bonferroni correction. Box plots charted for the findings did not suggest that the data was normally distributed and as a result, the groups were once again compared on their MoCA total scores, DCQ total scores and for all the DCQ’s indexes using a Mann-Whitney U test. This was followed by a second Bonferroni correction. Statistical analysis was performed using SPSS software (version 24.0) with the alpha level set at .05
