Evidence for a bimodal bilingual disadvantage in letter fluency

Enhancement of phonemic verbal fluency in multilingual young adults by transcranial random noise stimulation

Several studies have analyzed the effects of transcranial direct current stimulation on verbal fluency tasks in non-clinical populations. Nevertheless, the reported effects on verbal fluency are inconsistent. In addition, the effect of other techniques such as transcranial random noise stimulation (tRNS) on verbal fluency enhancement has yet to be studied in healthy multilingual populations. This study aims to explore the effects of tRNS on verbal fluency in healthy multilingual individuals. Fifty healthy multilingual (Spanish, English and Basque) adults were randomly assigned to a tRNS or sham group. Electrodes were placed on the left dorsolateral prefrontal cortex and left inferior frontal gyrus. All participants performed phonemic and semantic verbal fluency tasks before, during (online assessment) and immediately after (offline assessment) stimulation in three different languages. The results showed significantly better performance by participants who received tRNS in the phonemic verbal fluency tasks in Spanish (in the online and offline assessment) and English (in the offline assessment). No differences between conditions were found in Basque nor semantic verbal fluency. These findings suggests that tRNS on the left prefrontal cortex could help improve phonemic, yet not semantic, fluency in healthy multilingual adults.

A Systematic Review of Normative Data for Verbal Fluency Test in Different Languages

Verbal fluency tests are easy and quick to use in neuropsychological assessments, so they have been counted among the most classical tools in this context. To date, several normative data for verbal fluency tests have been provided in different languages and countries. A systematic review was carried out with studies that provide normative data for verbal fluency tests. Studies were collected from Scopus, PubMed and Web of Science. 183 studies were retrieved from the database search, of which 73 finally met the inclusion criteria. An analysis of the risk of bias regarding samples selection/characterization and procedure/results reports is conducted for each article. Finally, a full description of the normative data characteristics, considering country and language, verbal fluency task characteristics (type of task) and sample characteristics (number of subjects, gender, age, education) is included. The current systematic review provides an overview and analysis of internationally published normative data that might help clinicians in their search for valid and useful norms on verbal fluency tasks, as well as updated information about qualitative aspects of the different options currently available.

Does bilingualism come with linguistic costs? A meta-analytic review of the bilingual lexical deficit

A series of recent studies have shown that the once-assumed cognitive advantage of bilingualism finds little support in the evidence available to date. Surprisingly, however, the view that bilingualism incurs linguistic costs (the so-called lexical deficit) has not yet been subjected to the same degree of scrutiny, despite its centrality for our understanding of the human capacity for language. The current study implemented a comprehensive meta-analysis to address this gap. By analyzing 478 effect sizes from 130 studies on expressive vocabulary, we found that observed lexical deficits could not be attributed to bilingualism: Simultaneous bilinguals (who acquired both languages from birth) did not exhibit any lexical deficit, nor did sequential bilinguals (who acquired one language from birth and a second language after that) when tested in their mother tongue. Instead, systematic evidence for a lexical deficit was found among sequential bilinguals when tested in their second language, and more so for late than for early second language learners. This result suggests that a lexical deficit may be a phenomenon of second language acquisition rather than bilingualism per se.

Does bilingualism influence neuropsychological test performance in older adults? A systematic review

OBJECTIVE

Using standardized tests which have been normed on monolinguals for the assessment of bilinguals presents challenges to the accurate characterization of cognitive profile as the literature provides compelling evidence for the influence of bilingualism on cognitive abilities. However, little is known about the generalizability of these findings to clinical neuropsychology. The aim of this review was to address this gap by summarizing current evidence on the performance of bilingual older adults on standardized tests routinely used in clinical practice.

METHOD

A systematic search of Web of Science, PsycINFO and PubMed was conducted. 27 cross-sectional and longitudinal studies which use at least one standardized neuropsychological test for cognitive impairment were included in the review. Potential demographic (cultural/linguistic background of the participants, immigrant status), clinical (diagnostic status), and methodological confounders (language of test administration, components of bilingualism) were also examined. The review protocol was registered at the PROSPERO International Prospective Register of Systematic Review with registration number CRD42018114658.

RESULTS

The results of this review revealed some bilingual advantage on measures of inhibitory control and bilingual disadvantage on measures of verbal fluency in cross-sectional studies. Bilingualism status was not associated with test performance in longitudinal studies. However, findings lack consistency due to demographic variables and methodological differences across studies.

CONCLUSION

Neuropsychological tests assessing language domains and, to some extent executive function act as clinically relevant features of bilingualism for neuropsychological evaluation. However, immigration status, acculturation level and language of test administration needs to be taken into account when assessing bilingual older adults.

Using the DRM paradigm to assess language processing in monolinguals and bilinguals

Both languages are jointly activated in the bilingual brain, requiring bilinguals to select the target language while avoiding interference from the unwanted language. This cross-language interference is similar to the within-language interference created by the Deese-Roediger-McDermott false memory paradigm (DRM; Roediger & McDermott, 1995, Journal of Experimental Psychology: Learning, Memory, and Cognition, 21[4], 803-814). Although the mechanisms mediating false memory in the DRM paradigm remain an area of investigation, two of the more prominent theories-implicit associative response (IAR) and fuzzy trace-provide frameworks for using the DRM paradigm to advance our understanding of bilingual language processing. Three studies are reported comparing accuracy of monolingual and bilingual participants on different versions of the DRM. Study 1 presented lists of phonological associates and found that bilinguals showed higher rates of false recognition than did monolinguals. Study 2 used the standard semantic variant of the task and found that bilinguals showed lower false recognition rates than did monolinguals. Study 3 replicated and extended the findings in Experiment 2 in another semantic version of the task presented to younger and older adult monolingual and bilingual participants. These results are discussed within the frameworks of IAR and fuzzy-trace theories as further explicating differences between monolingual and bilingual processing.

The bilingual effects of linguistic distances on episodic memory and verbal fluency

The impact of linguistic distance or the relatedness between two languages, on bilinguals' episodic memory performance and verbal fluency is an understudied area. Thus, the purpose of this study was to determine if differences in linguistic distances have differential effects on these abilities. Measures of episodic recognition, categorical fluency, and global cognitive functioning were also considered in the analyses. Two matched samples with participants living and educated in Sweden were drawn from the Betula Prospective Cohort Study. Results showed that bilinguals who speak linguistically similar languages (Swedish and English), performed significantly better than monolinguals on both episodic memory recall and letter fluency, while bilinguals who speak two languages that are more distant (Swedish and Finnish), showed no advantages compared to their monolingual counterparts. For both tasks, however, a linear trend was observed indicative of better performance for the Swedish-English group compared to the Finnish-Swedish group, and for the Swedish-Finnish group compared to the monolinguals group. As expected, no differences between groups were found in any of the other cognitive tasks. Overall, results suggest that the impact of linguistic distances should be explored in more detail in the future.

Comparing Semantic Fluency in American Sign Language and English

This study investigated the impact of language modality and age of acquisition on semantic fluency in American Sign Language (ASL) and English. Experiment 1 compared semantic fluency performance (e.g., name as many animals as possible in 1 min) for deaf native and early ASL signers and hearing monolingual English speakers. The results showed similar fluency scores in both modalities when fingerspelled responses were included for ASL. Experiment 2 compared ASL and English fluency scores in hearing native and late ASL-English bilinguals. Semantic fluency scores were higher in English (the dominant language) than ASL (the non-dominant language), regardless of age of ASL acquisition. Fingerspelling was relatively common in all groups of signers and was used primarily for low-frequency items. We conclude that semantic fluency is sensitive to language dominance and that performance can be compared across the spoken and signed modality, but fingerspelled responses should be included in ASL fluency scores.