The relationship between cognitive flexibility, bilingualism and language production: evidence from narrative abilities in senior preschoolers from the Republic of Sakha (Yakutia)

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The relationship between cognitive flexibility, bilingualism and language production: evidence from narrative abilities in senior preschoolers from the Republic of Sakha (Yakutia)

E.S. Oshchepkova, A.N. Shatskaya,

M.I. Dedyukina, V.A. Yakupova, M.S. Kovyazina

Abstract

Bilingualism remains one of the key agents of influence on cognitive and language development of a child. Recently, this phenomenon became the focus of research attention. On the one hand, it can be explained by the active migration processes occurring on a global level. On the other hand, the influence of bilingualism over children's cognitive and language development is still quite a divisive issue. This study is aimed to explore, which phenomenon is more associ-ated with the language development, -- the fact of a child's bilingualism or his/her level of execu-tive functions development. 380 children from a bilingual Russian region participated in this re-search. The final sample consisted of 279 6--7-year-old subjects without deviations in their cogni-tive and language development. There were 181 monolingual children and 98 bilinguals. Age, gender and non-verbal intelligence were controlled. Average age equaled to 6.65 years (SD = 0.37). The study demonstrated that the differences revealed in the language development of monoand bilingual children were related mostly to lexical and grammatical aspects and didn't intervene with the macrostructure of the narrative. In regard to the influence of executive functions, the role of cognitive flexibility turned out to be an essential element from the perspective of the difference in monoand bilingual children's language development. As a whole, the study results allow drawing a conclusion that the development of cognitive flexibility contributes to a more efficient simultaneous mastering of two languages.

Keywords: narratives, bilingualism, language development, narrative's microstructure, narrative's macrostructure, executive functions, preschool age

Аннотация

Взаимосвязь между когнитивной гибкостью, билингвизмом и порождением речи на материале нарративов старших дошкольников из Республики Cаха (Якутия)

Е.С. Ощепкова И, А.Н. Шатская, М.И. Дедюкина, В.А. Якупова, М.С. Ковязина

Билингвизм остается одним из ключевых факторов, влияющих на когнитивное и языковое развитие ребенка. В последнее время это явление стало объектом пристального внимания исследователей. С одной стороны, это можно объяснить активными миграционными процессами, происходящими на глобальном уровне. С другой стороны, влияние двуязычия на когнитивное и языковое развитие детей по-прежнему вызывает разногласия: насколько оно сильно и можно ли нивелировать отрицательное влияние билингвизма. Данное исследование направлено на изучение того, какой фактор больше связан с языковым развитием -- факт двуязычия ребенка или уровень развития его регуляторных функций. В исследовании приняли участие 380 детей из двуязычного региона России. В окончательную выборку вошли 279 испытуемых в возрасте 6--7 лет без отклонений в когнитивном и языковом развитии. Респондентами стали 181 ребенок русскоязычный монолиингв и 98 русско-якутских билингвов. Факторы возраста, пола и невербального интеллекта также учитывались. Средний возраст детей составил 6,65 года (SD = 0,37). Исследование показало, что выявленные различия в языковом развитии однои двуязычных детей были связаны в основном с лексико-грамматическими аспектами и не влияли на макроструктуру нарратива. Что касается влияния регуляторных функций, роль когнитивной гибкости оказалась более важным элементом с точки зрения разницы в языковом развитии однои двуязычных детей. В целом результаты исследования позволяют сделать вывод о том, что развитие когнитивной гибкости способствует более эффективному одновременному овладению двумя языками.

Ключевые слова: нарративы, билингвизм, развитие речи, микроструктура нарратива, макроструктура нарратива, регуляторные функции, дошкольный возраст

Introduction

bilingual children cognitive language

Both the topic of the mutual influence of executive functions (EF) and language development, and the effect of bilingualism on children's speech and cognitive development, are of the utmost interest for contemporary psychology of education [1; 2]. The strongest results were obtained for the association of children's working memory (especially the verbal one) and language development [3; 4]. Some less obvious out-come was delivered on the effect of other components of executive functions, such as inhibition control and cognitive flexibility [5; 6].

Researchers focus on looking for specific factors that have a positive impact on the development of executive functions and speech development. Many phenomena may serve as such factors, for example, the features of the development of the emotional sphere affect the development of speech [7], and certain features and types of children's games are positively associated with the development of components of regulatory functions [8; 9].

At the same time, the question remains open as to whether there are any factors showing a negative impact on the development of self-regulation and speech in children. Even though bilingualism becomes a more and more influential factor for the entire system of preschool and junior school education [10], its effect on the language development within each mastered language remains a complex and yet, unsolved is-sue [11; 12]. For example, there is multiple data confirming the negative effect of bilingualism on vocabulary volume [11], but its relationship with other characteristics is still debatable [12]. Besides, it is important to keep in mind the diversity of bilingual-ism, in particular, when a child masters two languages belonging to different types and language families, for example, Russian and Yakut. Russian is a synthetic language where nouns, adjectives and verbs have three genders in the past tense [13]. Meanwhile, Yakut is an agglutinative language, and its grammar contains no category of gender whatsoever [14]. Therefore, due to these specifics, Russian-Yakut bilinguals often make mistakes in the agreement in gender when speaking Russian.

The Republic of Sakha (Yakutia) is a region of the Russian Federation where two languages, Russian and Yakut, coexist on the official level. Both communication and education is executed in two languages in a more or less equal proportion. Thus, in 32 kindergartens of the Republic there are both Russian-speaking and Yakutspeaking groups [15]. Capital residents have a slight preference for Russian, when in peripheral settlements (uluses) there are more monolinguals, speaking Yakut only. There are also kindergarten groups where children and adults prefer this or that language, along with totally bilingual groups, where everyone uses both languages.

The influence of bilingualism on executive functions

The influence of bilingualism on different EF was repeatedly studied by multiple researchers [16--18]. However, even our systematic review [18] demonstrated that this evidence is quite controversial, and more research is necessary in this area in order to clarify the conditions under which those effects show themselves. In general, there are both studies where bilinguals demonstrated better performance in cognitive flexibility and attention shifting [16], and where there was no difference at all [17]. We considered it important to include this aspect in our study, in order to ascertain the nature of this relationship.

Relationship of bilingualism and language development

The influence of bilingualism on language development was studied both in children with normal development, and the ones with different deviations [11; 12].

The outcome was also ambiguous. Generally speaking, one can claim that in children with developmental deviations, bilingualism often caused a negative effect on language development. We assume that the source of these ambiguous results lies in the extent of the difference of the languages mastered by the child, and with the aspect of language under study.

It has been proven that children narratives' analysis is a very precise language assessment tool for bilinguals [19]. It is common to distinguish macroand microstructure in narratives [20, 21]. The macrostructure includes general narrative parameters, narrative structure when the microstructure covers lexical, grammatical, and syntactic specifics of speech [21]. According to previous research of narratives in bilingual children [21--24], switching between languages will affect in the first hand the volume of a child's vocabulary, as well as his/her grammar and syntax (in case those two vary a lot from language to language). At the same time, general ability to build narratives with a certain structure doesn't depend on the presence of bilingualism, as it undergoes the same process independently from the language.

Relationship of language development and executive functions

The relationship of executive functions (EF) and language development often became of research interest, both in children with typical and atypical development and showed the strong relationships between these indicators [25--27]. Yet, it is important to point out that in the majority of such works mainly vocabulary and syntactical assessments were taken into consideration in order to estimate the language development [25; 27; 28]. Working memory as one of EF components showed the best connection with language development [26]. Furthermore, some evidence was obtained as well, regarding the association of the language development with cognitive flexibility and inhibitory control [5; 6] or with several components of EF [25; 27]. Besides, it was shown that verbal abilities had a significant effect on the development of regulatory functions in preschool children [29].

Previously, we studied the intercorrelation of EF and narratives using the narratives by monolingual children from other region of Russia [30, 31]. The analysis demonstrated, that in general, the level of proficiency of working memory was highly and stably correlated with the narrative macrostructure parameters; when verbal working memory was in particular connected with lexical and grammatical specifics of children's language. In regard to cognitive flexibility, the results revealed that there was a strong correlation between it and macrostructure indicators of narrative production whereas there were much fewer microstructure indicators that have correlations with cognitive flexibility. The children who were able to complete the most difficult task of DCCS method (with borders), showed better results in narrative production [32]. It is also of importance, that above mentioned research did not include the effect of bilingualism, and this is why we consider it as a crucial variable in the current study.

Aims and Hypotheses

The goal of this study was to reveal the influence of both bilingualism and executive functions on the language development of 6--7-year-old children. The results of literature review and our previous research works allowed us making the following hypotheses:

1) Monoand bilinguals demonstrate significant difference in the level of development of language and executive functions.

2) Advanced level of development of executive functions can counter-balance possible negative influence of bilingualism on the language development of preschool children. We expect cognitive flexibility to cause the highest compensating effect, comparing to the well-developed working memory (visual and audio-verbal) and inhibitory control.

Materials and Methods

Participants

Total sample for this study consisted of 380 participants. The data of 101 children was excluded from the analysis (see Data analysis for more details). The final sample size equaled to 279 6--7-year-old children with no cognitive or language development deviations (M = 6.65; SD = 0.37). There were 145 female and 134 male participants, all from the kindergartens of the Republic of Sakha (Yakutia). All subjects were divided in two groups. The first was monolingual (n = 181), i.e. consisted of children who, ac-cording to the educators' reports, spoke Russian only, and the educator spoke Russian to them as well. The second group was bilingual (n = 98); the children spoke Russian and Yakut, and the educator also addressed them in both languages.

Measures

Executive functions Assessment

Four subtests were used to assess different aspects of executive functions.

The subtest “Sentences Repetition” [33] aimed to assess verbal working memory. The child can receive from 0 to 34 points on it. The subtest “Memory for Designs” [33] aimed to assess visual working memory. There were four measurements available for children's visual working memory: a content score, a spatial score, a bonus score, and a total score (sum of previous three scores), in accordance with the NEPSY-II battery description.

The subtest “Inhibition” [33] aimed to assess inhibitory control as a component of executive functions which is the children's ability to inhibit automatized cognitive reactions. If there are no errors, the child receives two points for each five-second time interval; if there is one error, the child receives one point and 0 if there are two or more errors. The maximum number of points is 30.

The Dimensional Change Card Sort [34] is assessment of shifting or cognitive flexibility. DCCS implies children's sorting cards by different rules. One point is awarded for each correct sorting (the maximum of points is 24). Later each subtest was processed in accordance with the technique instruction [30].

Afterwards, a total score was calculated for each subtest, and it reflected the general level of development of a particular component of self-regulation system. For example, for the working memory subtest there was a “Total” score and the “Content”, “Spatial”, and “Bonus” scores. For audio-verbal memory subtest there was just the “Total score”. Inhibitory control subtest had a total “Naming” score for all the tasks series with different stimuli, and a total “Inhibition” score, also for all the series. Physical inhibitory control subtest (“hot self-regulation”) had a “Total” score and different measures for the mistakes of all types: “Movements”, “Eye opening”, and “Sounds”. For the last subtest, the one for cognitive flexibility, there was also a “Total” score and the measures for each sorting stage “Shape”, “Form”, and “With shifting”.

Language development assessment

We used elicited narratives for the assessment of language development. This technique is considered the most ecological [20; 21], because it allows taking into account not only the lexical and grammatical indicators of the child's language, but also his/her ability to compose structured coherent speech. However, despite all the advantages of this technique, the approaches to the collection, assessment, and the processing of narratives may still vary. In particular, the methods of the assessment of narratives, mostly applied in Russian psychology, include the following parameters: semantic completeness, semantic adequacy A and B [35], narrative type [36], and narrative structure [37]. In their aggregate, they represent the narrative macrostructure and lexico-grammatical parameters (lexical, grammatical and syntactical accuracy) that form the microstructure [31].

In the framework of the current study, we also distinguished complex parameters: 1) Narrative macrostructure that included semantic adequacy A and B, semantic completeness, narrative type, and narrative structure; and 2) Narrative microstructure (lexical, grammatical and syntactical accuracy).

In order to obtain more precise results, we used all types of elicited narratives: re-telling (“The jackdaw and the pigeons”), storytelling based on a single picture (“A broken cup”), and storytelling based on a series of pictures (“The cat and the dog”). All types of narratives were analyzed by the above listed parameters. All children were consequently presented with a picture, a series of pictures, and a story to be retold. All the narratives were recorded, and later these materials were written out by specially trained staff.

Strategy of Data Analysis

On the first stage, the initial sample of 380 6--7-year-old participants was reduced. We had to exclude the data of monolingual Yakut-speaking children (n = 101), as there was a possibility of misunderstanding the instructions, given that all the techniques were presented in Russian.

To confirm the first hypothesis, we used the method of comparison of averages for biand monolingual children by means of t-Student test and Mann-Whitney U test. The first test was used for cognitive flexibility “Total” score and “Shifting” score; for audio-verbal “Total” score, and some linguistic variables: semantic completeness, number of words, and macroand microstructure (general). The second test was applied to the number of cognitive flexibility mistakes in “Color” and “Shape” category; inhibition (naming and inhibition), physical inhibitory control, visual working memory, and the rest of linguistic variables: semantic adequacy A and B, narrative type, narrative structure, and lexical, grammatical and syntactical accuracy.

We used HCA in order to verify the second hypothesis. It allowed finding the optimal number of clusters in the EF development. Then we applied k-means clustering to define the groups with different levels of development of 1) cognitive flexibility; 2) working memory (visual and audio-verbal), and 3) inhibition.

Results

Differences in the Development of EF and Oral Language in Bilingual and Monolingual Preschoolers

Our first assumption, that there was a significant difference in language development and executive functions of monoand bilingual children, was verified through the comparison of averages (T-Student test and Mann--Whitney U test for independent samples). The following results were obtained for the relationship of self-regulation parameters. There were significant differences in audio-verbal memory of biand monolingual children, to the advantage of the latter (t = 5.046; p = 0.000). It meant that audio-verbal memory of bilingual respondents was less developed. In case of inhibitory control, the opposite significant differences were discovered, i.e., bilingual children had it on more advanced level (for the “Total” score, U = 6744.500; p = 0.024). The number of mistakes in that subtest also differed significantly: monolinguals made some sounds more often, even though the instruction to the task clearly prohibited it (U = 5576.500, p = 0.001). It can be explained with the fact that bilinguals have better skills of “hot” self-regulation. However, this conclusion is way too far-fetched, and clearly needs to be doublechecked on a larger sample.

The next step was to analyze the differences between monoand bilingual children in the level of their language development. Bilinguals demonstrated significantly lower score in all aspects of general narrative microstructure: lexical (U = 2354.0, p = 0.001), grammatical (U = 1738.5, p = 0.0001), and syntactical (U = 2190.5, p = 0.0001) accuracy. No significant difference was registered for narrative macrostructure. Thus, there were significant differences in biand monolingual children only with respect to lexical and grammatical accuracy of speech.

Language development in Bilinguals with High Level of Executive Functions

In our second hypothesis we assumed that bilinguals with advanced executive functions have the same level of language development as monolinguals.

Language development in Bilinguals with High Level of Cognitive Flexibility

We verified the second hypothesis regarding cognitive flexibility. For this, we de-fined the optimal number of clusters describing the values of cognitive flexibility, through hierarchic clustering. Two came out to be the best number. Next, we divided the whole sample in two groups by means of k-means clustering (medium and high level of development of cognitive flexibility, correspondingly). Significant difference between these two groups existed only for the following two parameters (T-Student test): “Total” score for cognitive flexibility (Total score Sorting: t = -14.781; p = 0.000) and shifting from one sorting rule to another (Sorting with Shifting: t = -13.603; p = 0.000). The difference between the high and medium CF for color and shape sorting were not significant (the Mann-Whitney test: U = 1914.0; p = 0.595 and U = 1780.0; p =.166).

Only monolingual (n = 84) and bilingual (n = 29) children with high level of cognitive flexibility development participated in the next stage of analysis. We performed the comparison of averages for linguistic variables with T-Student test and Mann--Whitney U test for independent samples. Obtained results can be found in Table 1.

Table 1 / Таблица 1

Comparison of Averages across monolinguals and bilinguals with High CF Level by linguistic variables / Сравнение средних показателей монолингвов и билингвов с высоким уровнем CF по лингвистическим переменным