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Abstract

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.

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According to some estimates, more than half of the world’s population is multilingual to some extent. Because of the centrality of language use to human experience and the deep connections between linguistic and nonlinguistic processing, it would not be surprising to find that there are interactions between bilingualism and cognitive and brain processes. The present review uses the framework of experience-dependent plasticity to evaluate the evidence for systematic modifications of brain and cognitive systems that can be attributed to bilingualism. The review describes studies investigating the relation between bilingualism and cognition in infants and children, younger and older adults, and patients, using both behavioral and neuroimaging methods. Excluded are studies whose outcomes focus primarily on linguistic abilities because of their more peripheral contribution to the central question regarding experience-dependent changes to cognition. Although most of the research discussed in the review reports some relation between bilingualism and cognitive or brain outcomes, several areas of research, notably behavioral studies with young adults, largely fail to show these effects. These discrepancies are discussed and considered in terms of methodological and conceptual issues. The final section proposes an account based on “executive attention” to explain the range of research findings and to set out an agenda for the next steps in this field.
Article
Many bimodal bilinguals are immersed in a spoken language-dominant environment from an early age and, unlike unimodal bilinguals, do not necessarily divide their language use between languages. Nonetheless, early ASL–English bilinguals retrieved fewer words in a letter fluency task in their dominant language compared to monolingual English speakers with equal vocabulary level. This finding demonstrates that reduced vocabulary size and/or frequency of use cannot completely account for bilingual disadvantages in verbal fluency. Instead, retrieval difficulties likely reflect between-language interference. Furthermore, it suggests that the two languages of bilinguals compete for selection even when they are expressed with distinct articulators.
Article
Within the current debates on cognitive reserve, cognitive aging and dementia, showing increasingly a positive effect of mental, social and physical activities on health in older age, bilingualism remains one of the most controversial issues. Some reasons for it might be social or even ideological. However, one of the most important genuine problems facing bilingualism research is the high number of potential confounding variables. Bilingual communities often differ from monolingual ones in a range of genetic and environmental variables. In addition, within the same population, bilingual individuals could be different from the outset from those who remain monolingual. We discuss the most common confounding variables in the study of bilingualism, aging and dementia, such as group heterogeneity, migration, social factors, differences in general intelligence and the related issue of reverse causality. We describe different ways in which they can be minimized by the choice of the studied populations and the collected data. In this way, the emerging picture of the interaction between bilingualism and cognitive aging becomes more complex, but also more convincing.
Article
In three immediate serial recall (ISR) experiments we tested the hypothesis that interactive processing between semantics and phonology supports phonological coherence in verbal short-term memory (STM). Participants categorised spoken words in six-item lists as they were presented, according to their semantic or phonological properties, then repeated the items in presentation order (Experiment 1). Despite matched categorisation performance between conditions, semantically-categorised words were correctly recalled more often than phonologically-categorised words. This accuracy advantage in the semantic condition was accompanied by fewer phoneme recombination errors. Comparisons with a nocategorisation ISR baseline (Experiment 2) indicated that, although categorisations were disruptive overall, recombination errors were specifically rarer following semantic categorisation. Experiment 3 replicated the key findings from Experiment 1 and also revealed fewer phonologically-related errors following semantic categorisation compared to a perceptual categorisation of high or low pitch. Therefore, augmented activation of semantic representations stabilises the phonological traces of words within verbal short-term memory, in line with the ‘‘semantic binding” hypothesis.
Article
This article describes the Betula Study with respect to objectives, design, participants, and assessment instruments for health and cognition. Three waves of data collection have been completed in 5-year intervals since 1988–1990. A fourth wave started in 2003 and will be completed in 2005. An overview of Betula research is presented under the headings of memory and cognition and cognitive neuroscience. Health-related issues and sex differences as well as comparisons between cross-sectional and longitudinal studies are discussed in the first section. The influence of different genes and of some brain abnormalities for memory functioning in adulthood and old age constitute main topics in the second section. New data are presented on the association between blood pressure and dementia. We demonstrated that a demented group of participants had higher levels of systolic blood pressure and pulse pressure than non-dementia controls 10 years before diagnosis. The new fourth wave of data collection will, in addition to enriching the Betula database, permit revisiting and reanalyzing the existing data from new perspectives.
Book
This book considers how languages have traditionally been divided into families, and asks how they should classified in the future. It describes and applies computer programs from biology and evolutionary genetics to data about languages and shows how the power of the computer can be harnessed to throw light on long-standing problems in historical linguistics. It tests current theories and hypotheses, shows how new ideas can be formulated, and offers a series of demonstrations that the new techniques applied to old data can produce convincing results that are sometimes startlingly at odds with accepted wisdom. April and Robert McMahon combine the expertise and perspectives of an historical linguist and a geneticist. They analyse the links between linguistic and population genetics, and consider how far language can be used to discover and understand the histories and interrelations of human populations. They explore the origins and formation of the Indo-European languages and examine less well studied languages in South America. Their book will be of great practical importance to students and researchers in historical and comparative linguistics and will interest all those concerned with the classification and diffusion of languages in fields such as archaeology, genetics, and anthropology. Its approachable style will appeal to general readers seeking to know more about the relationship between linguistic and human history.
Article
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.
Article
The objective of this article is to present an overview of a prospective cohort study involving a total of 3,000 subjects whose ages were 35, 40, 45, 50, 55, 60, 65, 70, 75, and 80 years when first tested. the design of the study includes three waves of data collection. the first of these waves was conducted in 1988-1990, the second in 1993-1995, and the third will be conducted in 1998-2000. One sample of 1,000 subjects in these age cohorts underwent testing in 1988-1990 (100 subjects per cohort). This sample and two additional samples were tested in 1993-1995 and will be tested again in 1998-2000. Subjects take part in extensive health and memory examinations, and interviews about social factors. the memory testing covers a wide range of memory functions. the chief objectives of the study are to (a) examine the development of health and memory in adulthood and old age; (b) determine early preclinical signs of dementia; (c) determine risk factors for dementia; and (d) assess premorbid memory function in subjects who are in accidents or acquire diseases during the course of the study. Cross-sectional data from the first sample show a continuous age-related deterioration in tasks assessing episodic memory, no age-related deficit in semantic memory tasks when educational level is partialed out, and no age effects in priming. Finally, the relationships between subjective (i.e., self-rating) and objective (blood and urine parameters, blood pressure and pulse, medication, recent contacts with a physician, and sensory function) indexes of health, on the one hand, and memory performance, on the other, were in general relatively weak in all age groups. the health-memory relationship was completely mediated by age, whereas the age-memory relationship was only partially mediated by health.
Article
The importance of the medial temporal lobe to episodic memory has been recognized for decades. Recent human fMRI findings have begun to delineate the functional roles of different MTL regions, most notably the hippocampus, for the retrieval of episodic memories. Importantly, these studies have also identified a network of cortical regions-each interconnected with the MTL-that are also consistently engaged during successful episodic retrieval. Along with the MTL these regions appear to constitute a content-independent network that acts in concert with cortical regions representing the contents of retrieval to support consciously accessible representations of prior experiences.
Article
The ability to remember events - referred to as episodic memory - is typically subject to decline in older adulthood. Episodic memory decline has been attributed in part to less successful executive functioning, which may hinder an older adult's ability to implement controlled encoding and retrieval processes. Since bilingual older adults often show more successful executive functioning than monolinguals, they may be better able to maintain episodic memory. To examine this hypothesis, we compared bilingual and monolingual older adults on a picture scene recall task (assessing episodic memory) and a Simon task (assessing executive functioning). Bilinguals exhibited better episodic memory than their monolingual peers, recalling significantly more items overall. Within the bilingual group, earlier second language acquisition and more years speaking two languages were associated with better recall. Bilinguals also demonstrated higher executive functioning, and there was evidence that level of executive functioning was related to memory performance. Results indicate that extensive practice controlling two languages may benefit episodic memory in older adults.
Article
The influence of adult foreign-language acquisition on human brain organization is poorly understood. We studied cortical thickness and hippocampal volumes of conscript interpreters before and after three months of intense language studies. Results revealed increases in hippocampus volume and in cortical thickness of the left middle frontal gyrus, inferior frontal gyrus, and superior temporal gyrus for interpreters relative to controls. The right hippocampus and the left superior temporal gyrus were structurally more malleable in interpreters acquiring higher proficiency in the foreign language. Interpreters struggling relatively more to master the language displayed larger gray matter increases in the middle frontal gyrus. These findings confirm structural changes in brain regions known to serve language functions during foreign-language acquisition.
Article
Building on earlier evidence showing a beneficial effect of bilingualism on children's cognitive development, we review recent studies using both behavioral and neuroimaging methods to examine the effects of bilingualism on cognition in adulthood and explore possible mechanisms for these effects. This research shows that bilingualism has a somewhat muted effect in adulthood but a larger role in older age, protecting against cognitive decline, a concept known as 'cognitive reserve'. We discuss recent evidence that bilingualism is associated with a delay in the onset of symptoms of dementia. Cognitive reserve is a crucial research area in the context of an aging population; the possibility that bilingualism contributes to cognitive reserve is therefore of growing importance as populations become increasingly diverse.
Article
Semantic dementia patients make numerous phoneme migration errors in their immediate serial recall of poorly comprehended words. In this study, similar errors were induced in the word recall of healthy participants by presenting unpredictable mixed lists of words and nonwords. This technique revealed that lexicality, word frequency, imageability, and the ratio of words to nonwords all influence the stability of the phonological trace. These factors affected phoneme migrations and phoneme identity errors for both the words themselves and the nonwords they were presented with. Therefore, lexical/semantic knowledge encourages the phonological segments of familiar words to emerge together in immediate serial recall. In the absence of such knowledge, the elements of a particular item are more likely to recombine with the phonemes of other list items. These findings demonstrate the importance of lexical and semantic binding in verbal short-term memory.
Article
Levenshtein distance has become a popular tool for measuring linguistic dialect distances, and has been applied to Irish Gaelic, Dutch, German and other dialect groups. The method, in the current state of the art, depends upon phonetic transcriptions, even when acoustic differences are used the number of segments in the transcriptions is used for speech rate normalization.The goal of this paper is to find a fully acoustic measure which approximates the quality of semi-acoustic measures that rely on tagged speech. We use a set of 15 Norwegian dialect recordings and test the hypothesis that the use of the acoustic signal only, without transcriptions, is sufficient for obtaining results which largely agree with both traditional Norwegian dialectology and the perception of the speakers themselves.We use formant trajectories and consider both the Hertz and the Bark scale. We experiment with an approach in which z-scores per frame are used instead of the original frequency values. Besides formant tracks, we also consider zero crossing rates: the number of times per interval that the amplitude waveform crosses the zero line. The zero crossing rate is sensitive to the difference between voiced and unvoiced speech sections.When using the fully acoustic measure on the basis of the combined representation with normalized frequency values, we obtained results comparable with the results obtained with the semi-acoustic measure. We applied cluster analysis and multidimensional scaling to distances obtained with this method and found results which largely agree with both the results of traditional Norwegian dialectology and with the perception of the speakers. When scaling to three dimensions, we found the first dimension responsible for gender differences. However, when leaving out this dimension, dialect specific information is lost as well.
Article
While functional changes linked to second language learning have been subject to extensive investigation, the issue of learning-dependent structural plasticity in the fields of bilingualism and language comprehension has so far received less notice. In the present study we used voxel-based morphometry to monitor structural changes occurring within five months of second language learning. Native English-speaking exchange students learning German in Switzerland were examined once at the beginning of their stay and once about five months later, when their German language skills had significantly increased. We show that structural changes in the left inferior frontal gyrus are correlated with the increase in second language proficiency as measured by a paper-and-pencil language test. Contrary to the increase in proficiency and grey matter, the absolute values of grey matter density and second language proficiency did not correlate (neither on first nor on second measurement). This indicates that the individual amount of learning is reflected in brain structure changes, regardless of absolute proficiency.
Article
When estimating causal effects using observational data, it is desirable to replicate a randomized experiment as closely as possible by obtaining treated and control groups with similar covariate distributions. This goal can often be achieved by choosing well-matched samples of the original treated and control groups, thereby reducing bias due to the covariates. Since the 1970's, work on matching methods has examined how to best choose treated and control subjects for comparison. Matching methods are gaining popularity in fields such as economics, epidemiology, medicine, and political science. However, until now the literature and related advice has been scattered across disciplines. Researchers who are interested in using matching methods-or developing methods related to matching-do not have a single place to turn to learn about past and current research. This paper provides a structure for thinking about matching methods and guidance on their use, coalescing the existing research (both old and new) and providing a summary of where the literature on matching methods is now and where it should be headed.
Article
We use a time-course analysis to examine the roles of vocabulary size and executive control in bilinguals' verbal fluency performance. Two groups of bilinguals and a group of monolingual adults were tested in English with verbal fluency subtests from the Delis-Kaplan Executive Function System. The two bilingual groups were equivalent in their self-rated English proficiency but differed in levels of receptive and expressive vocabulary. We hypothesized that the difference between the two bilingual groups in vocabulary and between the monolingual and bilingual groups in executive control would lead to differences in performance on the category and letter fluency tests and dissociate the roles of vocabulary knowledge and executive control in verbal production. Bilinguals and monolinguals performed equivalently in category fluency, but the high-vocabulary bilingual group outperformed both monolinguals and low-vocabulary bilinguals in letter fluency. An analysis of the retrieval time-course functions in letter fluency showed dissociable effects of resources available at the initiation of the trial, considered to reflect vocabulary size, and ability to monitor and retrieve new items using a novel phonemic-based word searching strategy, considered to reflect executive control. The difference in slope of the best-fitting curves reflected enhanced executive control for both bilingual groups compared to monolinguals, whereas the difference in the starting point of the logarithmic functions reflected higher levels of vocabulary for high-vocabulary bilinguals and monolinguals compared to low-vocabulary bilinguals. The results are discussed in terms of the contributions of linguistic resources and executive control to verbal performance.
Article
The "weaker links" hypothesis proposes that bilinguals are disadvantaged relative to monolinguals on speaking tasks because they divide frequency-of-use between two languages. To test this proposal we contrasted the effects of increased word use associated with monolingualism, language dominance, and increased age on picture naming times. In two experiments, younger and older bilinguals and monolinguals named pictures with high- or low-frequency names in English and (if bilingual) also in Spanish. In Experiment 1, slowing related to bilingualism and language dominance was greater for producing low- than high-frequency names. In Experiment 2, slowing related to aging was greater for producing low-frequency names in the dominant language, but when speaking the nondominant language, increased age attenuated frequency effects and age-related slowing was limited exclusively to high-frequency names. These results challenge competition based accounts of bilingual disadvantages in language production, and illustrate how between-group processing differences may emerge from cognitive mechanisms general to all speakers.
Article
We investigated whether 59 allele frequencies and 10 cranial variables differed among speakers of the 12 modern language families in Europe. Although this is a classical analysis of variance design, special techniques had to be developed for the analysis because of spatial autocorrelation of both biological and language data. The method examines pooled sums of squares within language families. These are compared with the same quantities obtained by randomly partitioning the available data points in Europe into internally cohesive subsets representing the same sample sizes for each language family as in the originally observed data. Our results suggest that for numerous genetic systems, population samples differ more among language families than they do within families. These findings are considered in relation to two contrasting models: a model of random spatial differentiation of gene frequencies unrelated to language and a model of aboriginal genetic differences among speakers of different language groups. Our observed findings suggest partial validity of both models.