Lexical Access and Working Memory in Bilinguals: A ...

Lexical Access and Working Memory in Bilinguals: A Partial Replication Sandra Marín Sancho1 The University of Illinois at Chicago

1

The experiments and data present in this research have been accomplished and gathered together with the MA student Paula Motrico San Emeterio.

Abstract

The present study presents a partial replication of Bialystok et al. (2008) examining lexical retrieval and working memory differences between bilinguals and monolinguals. Two specific tasks were selected among those administered by Bialystok et al. (2008) measuring lexical access differences and working memory capacity for both language groups. Additionally, the study also examines possible correlations between the performance on lexical access task and WM capacity of participants in order to elucidate potential differences between language groups. Results showed that monolinguals outperformed bilinguals in lexical retrieval in one language while the employed WM task did not report any significant difference between groups. Also, results did not show any correlation between lexical access and WM capacities. These findings replicate Bialystok et al. (2008) and are attributable to the cross-linguistic interaction theory and to how the need to manage two language systems can lead to different outcomes in linguistic and cognitive functions between groups.

Keywords: Bilingual, Monolingual, Lexical Access, Working Memory.

1 Introduction The extent to which the brain of a bilingual processes language differently from that of a monolingual has been a debated topic in bilingualism and cognition research. In fact, research with adult bilinguals reported that the verbal skills of bilinguals in one of the languages are generally weaker than are those for monolingual speakers of such language. Considering simply receptive vocabulary size, bilinguals control a smaller vocabulary in the language of the community than do their monolingual counterparts (Bialystok et al. 2008). In line with this suggestion, research found that bilingual children made more errors in picture naming activities (Gollan et al. 2005) and that bilingual children also obtained reduced scores in letter and category fluency tasks (Roberts et al. 2002). Notwithstanding, these debates on disadvantage on lexical retrieval for bilinguals agree that both languages are active and influence each other in bilingual speech (Costa et al. 2006). Therefore, lexical retrieval is more demanding for bilinguals since both languages are active and interacting while producing either language, demanding some selection or attention on the targeted language. Additionally, another essential cognitive ability involved in executive processing is Working Memory (WM). In contrast to the lexical retrieval disadvantage, bilinguals at all ages demonstrate better executive control than monolinguals matched in age and other background factors (Bialystok et al. 2012). Executive control is the set of cognitive skills based on limited cognitive resources for such functions as inhibition, switching attention, and working (WM). The suggestion that bilinguals are particularly adept at maintaining the appropriate one of two (or more) relevant task goals or attentional sets in working memory has much in common with the notion of selection of wanted stimuli as opposed to inhibition of unwanted ones (Bialystok et al. 2012). Since bilinguals undergo more difficulties in lexical access, it could be assumed that bilinguals possess superior working memory abilities (Bialystok et al. 2004). However, results on different studies suggest that

2 there are no clear advantages or disadvantages for bilinguals on working memory (Christoffels & de Groot, 2005; Bajo et al. 2000). In summary, evidence indicates that bilinguals face a conflict in lexical retrieval since both languages remain active, requesting some type of attention on the targeted language. This need for a specific attention, is the result of analyzing only one of the language of bilinguals, since for these individuals every word has half the frequency as for a monolingual. However, the extent to which the demands on working memory are greater for bilinguals remains to be seen. Therefore, the present study was designed to replicate the study carried out by Bialystok et al. (2008) expecting to, in line with their results, demonstrate that bilinguals are subject to a more demanding lexical access in comparison to monolinguals and that both groups do not differ in excess when it comes to working memory abilities. This replication aims to substantiate their results with bilinguals of a different population, adding more validity and reliability to their findings and providing a clearer description of the effects of bilingualism on cognitive processing. Review of the literature Lexical Access in Bilinguals To fully motivate the current study, we first examine research on lexical access in bilinguals. Field (2003) defined lexical access as the way which individuals access words in the mental lexicon, this is, how individuals look for specific vocabulary that is stored in the mind in the form of individual lexical entries. Although every person can access their lexicon to communicate, there is some debate about the difference between how bilinguals and monolinguals retrieve lexicon. In fact, there is evidence that bilinguals are subject to decrements and more difficulties in lexical access since they activate both languages in parallel when they are using only one of them. In other words, referring to one lexicon results

3 more demanding for bilinguals, since both languages are active and influence each other constantly in their speech, having to inhibit the “not targeted” language (Costa et al. 2008). This disadvantage in contrast with monolinguals can be observed when bilinguals are involved in tasks that require fast access to one of the languages. For instance, several studies investigating linguistic performance has reported vocabulary deficits for fluent bilinguals in picture naming activities (Gollan et al. 2005). This is, bilingual in these studies recalled fewer vocabulary items in such tasks. These results seem to be consistent with previous studies that had shown monolingual advantage over bilingual lexical access appealing to reaction time measures. Reaction time (RT) measurement is known to provide valuable insight into the different patterns of syntactic processing that second monolinguals and bilinguals manifest. Following this measure, bilinguals show longer gaze-durations to target items when reading sentences compared to monolinguals (Gollan et al. 2011), slower RTs than monolinguals in lexical decision tasks (Duyck et al. 2008; Gollan et al. 2011), and slower N2 and N400 responses when judging target word length (Martin et al. 2011). Moreover, slower lexical processing has also been observed during language production for bilinguals (Gollan et al. 2011; Ivanova and Costa 2008; Kohnert et al. 1998). The study aimed to be replicated, Bialystok et al. (2008), found congruency with previous findings: monolinguals outperformed bilinguals in verbal tasks involving fast lexical retrieval in one language. In order to assess the experiments, they implemented three different tasks involving lexical retrieval: Peabody Picture Vocabulary Test (PPVT) III Form B, Boston naming task and Category (animal) and letter (FAS) task. The results obtained from all three verbal tasks indicated a superiority of lexical retrieval for monolinguals. In summary, previous research provides evidence that indicates that bilingualism is associated with disadvantages in verbal fluency since both language systems remain active

4 for the latter group. Therefore, bilinguals are constantly exposed to an effort that monolinguals are not subject to: lexical choice in rapid lexical retrieval. To present further data supporting these claims, the present conceptual replication includes the Category (animal) and letter (FAS) verbal fluency task previously assessed in Bialystok et al. (2008). Working Memory in Bilinguals Another important mediating factor considered in Bialystok et al. (2008) is Working Memory (WM), however, the extent to which this mechanism differs from bilinguals to monolinguals remains uncertain. WM, generally viewed as the ability to maintain information in an active and readily accessible state, while concurrently and selectively processing new information (Conway et al. 2007, p.3), has been considered a crucial cognitive construct in human cognition and has been extensively researched in cognitive psychology. Working memory is completely integrated into descriptions of linguistic processing as the base for tasks as comprehension of written and spoken texts and fluency in language (Gernsbacher et al. 1991). Previous studies examining the relationship between bilingualism and working memory (WM) have reported differing results. For instance, some studies (Bialystok et al. 2004) found some evidence for superior working memory abilities in bilinguals. These findings indicate that WM is not totally unaffected by the different production demands of bilingualism but that a bilingual advantage may exist in specific aspects of WM. However, strong evidence claiming that bilinguals poses WM advantages, is less frequently found in the literature in contrast to studies yielding no overall benefits in specific tasks or conditions for both groups. This is also true of comparisons between different bilingual groups who daily complete different levels of demand on their WM systems (for instance, simultaneous interpreters vs. non-interpreting bilinguals perform differently in terms of lexical access and cognitive demands as indicated by Bajo et al. (2000). For

5 example, Engel de Abreu (2011) concluded that “bilingual experience does not seem to convey any advantage in working memory abilities,” which aligns with recent criticism on the very notion of bilingual benefits (Duñabeitia and Carreiras, 2015). In line with these findings, the study aimed to be replicated, Bialystok et al. (2008), reports a small difference in the WM between bilinguals and monolinguals, slightly favoring bilinguals. However, this tiny difference is reported as statistically insignificant, suggesting that this domain is impervious to bilingualism. In fact, Bialystok et al. (2008) reported language group differences only for the oldest participants, this is, the primary difference in performance on the WM task was that older participants recalled fewer items than their young counterparts. However, the more general question of whether bilingualism affects working memory performance in any task or situation remains somewhat open (Bialystok et al. 2008) In summary, the hypothesis underlying the field is that cognitive skills developed to cope with the demands of controlling two languages can generalize to more efficient processing in executive domains like WM. To further explore the relation between WM and bilingualism, the current replication study includes a working memory test: the same used in Bialystok et al. (2008), Corsis Span task. The present study aims to follow Bialystok et al. (2008)’s steps by conducting a conceptual replication focusing on lexical access and working memory differences between bilinguals and monolinguals. To assess this matter, two language groups are tested both in lexical retrieval capacities and in working memory. Unlike the original study, the present analysis does not compare age groups, it focuses on young bilinguals and monolinguals and the differences performed on the two different tasks. Therefore, the research questions motivating the study are: RQ1: Does bilingualism affect lexical access?

6 RQ2: Does working memory (WM) differ from monolinguals to bilinguals? If so, is it correlated with the lexical retrieval process for both groups? Based on these research questions and guided by the results found on previous literature and in Bialystok et al. (2008), we expect to find greater fluency (shorter latencies in lexical access) within the monolingual group than in the bilingual group. On the other hand, following findings on previous literature, one could expect no statistically significant differences on WM between the compared two language groups. Method Participants There were a total number of 15 participants (4 were males) divided among 6 monolinguals in English (M = 27.5 SD = 6.18) and 9 bilinguals (M = 21.4 SD = 3.35) in English and a variety of L2s as illustrated in Table 1 in the appendices. The non-English language of the bilinguals included Polish (2), Spanish (4), Arabic (2) and Korean (1). In order to be taken into account for the study, bilinguals had to report a daily use and exposure to both languages from birth. The group of bilinguals were all Heritage Speakers and started speaking English before the age of 3 years. With this profile, it is difficult to assign the classification of first language (L1) and second language (L2) to the bilinguals, especially since they learned English before the age of 3 and used English for schooling and social life, which is likely to make them more dominant in English (Bialystok et al. 2008). On the other hand, the monolingual group was formed upon participants who reported not using any other language but English and having taken no more than two semesters of any L2 in addition to no experience in any Study Abroad program.

7 Both language groups completed a linguistic questionnaire1 created by the Language Learning center at the University of Texas at Austin by the end of the session in which they reported their language use, language history, attitudes and proficiency. A demographic questionnaire regarding ethnicity, place of birth, current place of residence and level of education was also provided to participants at the end of the session. Table 2 in the appendix shows means and standard deviations for some of the questions regarding language use among bilinguals. Materials The partial replication of Bialystok et al. (2008) that the present study depicts focused on two specific tasks assessing working memory and lexical access from those assessed in the cited study. As previously mentioned, Bialystok et al. (2008) conducted an analysis of three different lexical retrieval tasks (Peabody Picture Vocabulary Test (PPVT) III, Form B; Boston naming task and Category (animal) and letter (FAS) fluency), two executive control tasks (Simon arrows task and Stroop color-naming task) and two working memory tasks (Forward and backward Corsi blocks and Self-ordered pointing). The current study aims to replicate two of these studies: the Category (animal) and letter (FAS) task to measure lexical access in bilinguals and monolinguals; and the forward Corsi blocks task in order to measure the working memory of the participants. Lexical Retrieval Assessment: Category (Animal) and letter (FAS) task In order to measure the differences between both language groups when accessing their lexicon systems, we implemented the Category and letter task. Following Bialystok et al. (2008) steps, participants in both groups were requested (orally and in written) to produce as many words as they were able to within one minute starting with the letter F, A and S.

1

Both questionnaires (the one implemented for the bilingual group and the one for the monolingual group) are

included in the appendices.

8 Unlike Bialystok et al. (2008) the current study randomized the order in which the letters (F, A, S) were presented to each participant to add validity to the task. Afterwards, participants were also asked to produce as many words as they were capable of within a specific category: animals. For transcription and coding purposes, participants were audiotaped while producing words. Participants were previously informed that family words (getgot, keep-kept) and plural forms of each item would not be considered for the study. This traditional methodology was followed to keep as close as possible to the materials administered by Bialystok et al. (2008). Additionally, participants were timed for one precise minute with a stop watch during the elicitation task. Exactly as the cited authors, we analyzed the letter and category task separately and reported the Lexical Access score as the total number of words produced by group. Therefore, the current study focused on the Category and letter task to examine the previously reported bilingual deficit in lexical retrieval in more detail among participants. Working Memory Assessment: Forward Corsi blocks task Bialystok et al. (2008) argued that the need of bilingual speakers to manage two languages at the same time may carry greater demands for WM. However, their results concluded that there was no significant difference between language groups for this variable. In accordance with the study aimed to be replicated, the present study aimed to analyze any possible WM differences between the groups. In order to measure such differences, we centered in one specific task assessing WM: Forward Corsi blocks task. This task was designed online in order to measure the WM capacity required by each participant to memorize the sequence in which some cubes lighted up. This is, participants would be presented with several dark cubes lighting up one by one and right after, they would need to click on them following the exact same order in which they lighted up. These set of cubes were presented in several sequences, and each sequence would increase its complexity

9 by one cube every second trial. WM scores were represented by the total number of blocks the participant got to memorize in the last sequence correctly reproduced. Procedures and Analysis Data were collected in one single session in which participants would (a) fill the appropriate IRB consent forms, (b) run both tasks and (c) complete a linguistic and a demographic background questionnaire. For the completion of both tasks in question, participants were first asked to carry out the lexical access task Category (Animal) and letter (FAS) task, and right after, they would execute the WM Forward Corsi blocks task. All participants followed the same procedure and by the end of the processes, each would have (i) a number of produced items with each letter, (ii) a number of items produced within the animal category in the same lexical task, and (iii) a number corresponding to their score on the WM blocks task. Finally, in order to proceed to analyze the gathered data, scores on the lexical access task and scores on the WM block task were separated and individually analyzed for each language group. Descriptive analysis as well as statistical analysis were conducted for each variable and containing all scores for each language group. In order to compare the bilingual group’s scores with the monolingual group’s scores on the lexical access task, we run a t-test comparing them. Moreover, since the collected data for the WM task was not normally distributed, we implemented a t-test which did not report valid results. Therefore, a Mann Whitney U test was executed to compare both language groups in terms of WM scores. This tool is a nonparametric test of the null hypothesis and that unlike the t-test, it does not require the assumption of normal distributions. It is considered to be nearly as efficient as the t-test on normal distributions (Fay et al. 2010).

10 Furthermore, unlike Bialystok et al. (2008), we also looked for any possible correlation between WM scores and lexical access results between language groups. To assess this, we applied a Spearman’s rho bivariate correlation test. Results Verbal Task Results were divided in two sections to analyze lexical access scores, WM scores and a potential correlation between both at the end. Table 3 in the appendix shows the mean and standard deviation values for the FAS-Category task to address lexical access in both groups. A significant difference in the mean score of words produced by monolinguals compared to bilinguals is noticeable in FAS task but not so much in the Category task. A Shapiro-Wilk (SW) test was executed reporting (SW = .909, df = 6, p = .428) skewness (-.634) and kurtosis ratios (-.640) for a normally distributed data for the total lexical access scores for both tasks together: Letter and Category. Therefore, we run a t- test reported that monolinguals generated overall more items than bilinguals for both letter, p < . 003, but there were not significant differences in the Category Task between groups. The confidence intervals for the Letter task showed no overlap between 95% CIs [47.5, 62.4] for monolinguals and 95% CIs [32.2, 43.5] for bilinguals, which indicates that there was a difference between groups. On the other hand, the 95% CIs [18.5, 25.8] for monolinguals and 95% CIs [18.6, 26.4] for bilinguals in the Category task overlap almost completely which suggest that there is no difference between groups. This results replicate previous research showing a general monolingual advantage for verbal tasks (Bialystok et al. 2008). Such research reported that regarding the letter task, monolinguals (M= 49.8, SD = 7.4) outperformed bilinguals (M= 42.4, SD = 11.1) but a not so clear advantage for the Category task, where monolinguals (M=23.3, SD =5.4) retrieved not as many items than the bilingual group (M= 21.3, SD = 3.8). Table 4 illustrates the inferential statistic results obtained from the t-test in order to compare bilinguals’ scores with the monolinguals’ scores on the lexical

11 access task. A significant advantage for the monolingual group in the overall score for this task was reported. Working Memory Task When comparing the 95% CIs [4.3, 6.5] for the monolingual group and 95% CIs [5.7, 7.2] for the bilingual group in terms of WM, there existed an overlap indicating that there were no significant differences for WM between language groups within the Corsi block task. Notwithstanding, the mean was slight difference for one of the language groups. Bilinguals got higher scores in this task, however, the overlapping digits of the Confidence Intervals indicate that this difference is not significant. Table 5 reflects these differences within WM capacities across groups. In order to statistically compare both groups within WM capacities according to the Corsi block task, a t-test was applied to the results. However, even if results were approaching significance (p = .079), the statistical analysis did not show any statistically significant difference between groups. The Shapiro-Wilk (SW) test suggested that these data were not normally distributed: (SW = .830, df = 9, p = .045) and skewness (.655) and kurtosis ratios (-.425) for bilingual group and (SW = .771, df = 5, p = .046) and skewness (-1.258) and kurtosis ratios (-.313) for the monolingual group. Thus, we administered a non-parametric test: Mann Withney U test. In line with Bialystok et al. (2008), this independent sample test did not report any significant difference between language groups (p = 1.47). Figure 1 illustrates the slight differences between bilinguals and monolinguals in the current study and Figure 2 shows does so for Bialystok et al. (2008). In regards of the possible correlation between WM scores and number of items produced in the Lexical Access task by language group, we implemented a Spearsman rho correlation test. Results did not report any statistical correlation between these variables neither for bilinguals p = .888 nor for monolinguals p = .450. As it can be observed in Figure 3 and 4, there was no clear pattern guiding any possible correlation.

12 In line with the replicated study, these irregular patterns could be suggesting that those participants who show greatest access difficulties are not necessarily the ones who show greatest advantages in WM. In fact, in accordance with previous literature on the matter, this correlation does not reveal the extent to which bilinguals and monolinguals WM capacities differ and neither if they are somehow related to vocabulary retrieval difficulties. Discussion The present study was designed to partially replicate some of the findings reported by Bialystok et al. (2008) regarding lexical access and working memory differences between bilinguals and monolinguals. For this, participants completed a couple of tasks measuring these variables. The findings suggest that, in accordance with Bialystok et al. (2008), bilingualism indicates processing differences on individual tasks. This is, monolinguals and bilinguals performed largely equivalently on the working memory task while monolinguals performed better on the task measuring lexical retrieval. As for our firstly posed RQ, does bilingualism affect lexical access?, results showed a significant monolingual advantage in one language, confirming the pattern reported by Bialystok et al. (2008). According to the authors, there are two possible explanations for bilinguals to produce less vocabulary items than monolinguals. The first follows from the salient difference between monolinguals and bilinguals in the experience on the employed language (English). In fact, for bilinguals every word has half the frequency as for a monolingual, since the other half is likely to be processed in the L2. This explanation is plausible and consistent with research indicating how salient the role of frequency effects on performance in SLA providing explanation for bilinguals’ lower production of lexical items (Hernandez & Li, 2007). The second appealing explanation is that such effort to produce as many lexical items as the monolingual group resides in the cross- linguistic theory. This theory states that in the case of bilinguals, the two languages are known to interact and mutually influence each other throughout the processing stream, with bilinguals frequently borrowing (Myers-Scotton,

13 1992), transfering (Gass, 1996; Jarvis & Odlin, 2000; Jones, 2005; Treffers-Daller & Mougeon, 2005), and code switching1 (Poplack, 1980) from one language into the other. Although most studies of transfer have focused on the interaction influence of first language (L1) on second language (L2), recent research suggests that language interaction is bidirectional, and that the L2 can also influence the L1 (Bernardini & Schlyter, 2004; Heredia & Altarriba, 2001). More specifically, bilinguals might have competing responses when accesing their lexicon between their two languages. This is, lexical representations may be intact in bilinguals, but response production may be affected by the need to inhibit interference from the untargeted language (Bialystok et al. 2008). This account explains the lower production of words within the lexical task. On

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analysis also replicated the results previously reported by Bialystok et al. (2008). In fact, although WM scores were similar between both tested language groups, there appeared to be a small advantage for bilinguals (M = 6.4, SD = 0.3) when compared to monolinguals (M= 5.4, SD = 0.8). These results replicate Bialystok et al. (2008) who reported a slightly higher WM score for bilinguals (M = 3.8, SD = 1.2) compared to monolinguals (M = 3.3, SD = 0.9). However, as expected, these small differences were not statistically significant. Therefore, it would be interesting to see whether this advantage in WM is an extension of the bilingual advantage generated for the executive control in order to clarify whether both components and only one of them are affected by bilingualism. Although, this task was designed, according to the literature (Bialystok et al. 2008), to involve executive control functions where bilingual advantages might be expected, this was not the case. Therefore, the general question of whether bilingualism affects WM performance remains somewhat open. There are some indications suggesting that WM is a family of constructs rather than a unitary entity (Daneman & Tardif, 1987), indicating that there may be

14 a need to implement different WM aspects to cover every WM feature possibly affected by the effects of bilingualism. In accordance with Bialystok et al. (2008), we await further evidence and research on this matter before drawing any possible conclusion as well as for our 3rd RQ regarding the possibility of a correlation between lexical retrieval process and WM capacities for both groups.

Limitations Besides providing consistent data partially replicating Bialystok et al. (2008)’s results, the current study is subject to multiple limitations and improvements. One of the most crucial improvements for further research is the small sample of participants involved. The study counted with a reduced cipher of 9 bilingual participants and 6 monolinguals. Further research would benefit from a larger pool of participants in order to provide statistical significance and validity to the study. Moreover, both language groups should contain an equal division in terms of gender, age and level of studies to better control for these factors. Another limitation that possibly influenced the lower amount of words produced by bilinguals in the verbal task is the use of English as the only language for such task. Staying close to the methods implemented by the replicated study, both language groups were asked to produce vocabulary items within the common language. This fact possibly resulted in the lower production of items for bilinguals in contrast to monolinguals since we did not test bilinguals in their L2, obtaining results for only one of their language systems. It could be expected to encounter the same or more quantity of vocabulary items in bilinguals if they had been tested in both languages.

15 Moreover, due to the fact that the current replication only attested two tasks, it may be too broad to state that this study is a ‘replication’ of Bialystok et al. (2008). Future research should elaborate and test with the same tools as the authors in order to reliably substantiate their findings. Additionally, further research should implement different and more varied (if possible) WM test in order to tap every WM component affected by bilingualism and provide a more accurate description of this question.

Conclusions In sum, the current study presents a partial replication of the detailed description of the cognitive effects of bilingualism realized by Bialystok et al. (2008). Consistent with their results, monolinguals outperformed bilinguals in lexical retrieval when tested in the common language for both groups: English. This difference was predicted, since our bilingual group was not tested in all their linguistic abilities, but only in half of them (one language only). Moreover, results regarding WM differences were in accordance with previous research indicating no clear differences for this variable between language groups (Bialystok et al. 2008; Bialystok et al. 2004; Engel de Abreu; 2011), leaving the question of whether WM is somehow affected by bilingualism open. Finally, in regards of our posed last RQ, whether there was a correlation between the two variables in question (WM & Lexical Access), results in the present study could not report such correlation. Even if the present results endorse a functional conception of mind in which language and cognitive processes are integrated, the extent to which there exists a possible correlation between these two variables is subject for further study.

16

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