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Bilingualism as a Purported Risk Factor for Stuttering: A Close Look at a Seminal Study (Travis et al., 1937)

2020; American Speech–Language–Hearing Association; Volume: 63; Issue: 11 Linguagem: Inglês

10.1044/2020_jslhr-20-00364

1558-9102

Susanne Gahl,

Neurobiology of Language and Bilingualism

Open AccessJournal of Speech, Language, and Hearing ResearchCommentary13 Nov 2020Bilingualism as a Purported Risk Factor for Stuttering: A Close Look at a Seminal Study (Travis et al., 1937) Susanne Gahl Susanne Gahl https://orcid.org/0000-0003-1293-7899 Department of Linguistics, University of California at Berkeley Google Scholar https://doi.org/10.1044/2020_JSLHR-20-00364 SectionsAboutAbstractPDF ToolsAdd to favoritesDownload CitationTrack Citations ShareFacebookTwitterLinked In Does bilingualism elevate the risk of stuttering? Whenever this question is discussed in the literature, one particular study (Travis et al., 1937) is almost invariably cited. Is this citation pattern warranted? Quite a few studies, discussed below, have pointed out shortcomings in Travis et al.'s methods. Yet, the citation pattern has persisted. Travis et al. reported a stuttering prevalence of 1.8% for monolingual school children and 2.8% for bilingual ones, a difference they found to be statistically significant. Many sources citing Travis et al. quote these figures. Some (e.g., Szmalec, 2013, among many others) cite them as evidence for a causal link between bilingualism and stuttering. Others note, neutrally, that these figures have been considered by other authors to constitute evidence for such a link (e.g., Choo & Smith, 2020; Proctor et al., 2008; Schneider, 2015; Yairi & Ambrose, 2013) and/or point out methodological flaws in the study (e.g., Bloodstein & Bernstein Ratner, 2008; Van Borsel, 2011; Van Borsel et al., 2001). No matter what position one takes in this matter, the reported clear difference in stuttering prevalence among monolingual versus bilingual children is striking and noteworthy, particularly given its practical implications for bilingual families. However, a difference should only be noteworthy if it is supported by the data. Here, we ask whether it was in fact the case that 1.8% of the monolingual group, versus 2.8% of the bilingual group, in Travis et al. (1937) stuttered.1 We then ask to what extent small discrepancies in the data affect the statistical significance of the results. To preview our results: We find that the raw counts and prevalence rates reported in Travis et al. are internally inconsistent. Among other problems, it appears that the 1.8% versus 2.8% difference is due to several stuttering children being excluded from the prevalence estimate for the monolingual group. In addition, we find that the statistical significance of the results rests on the classification of very small numbers of participants—far smaller than the uncertainties in the reported numbers. Travis et al. (1937): Methods and Criticisms Travis et al. (1937) surveyed nine schools in East Chicago, Indiana, primarily focusing on stuttering, but also including "foreign accent," "letter substitution," "oral inactivity," and "aphasia." The children ranged in age from 4 to 17 years. The reported average age was 8.54 years, and the reported sample size was 4,827. Each child was given a questionnaire asking what languages were spoken in the child's home and what proportion of the child's "home speech" and "school speech" was in English. The questionnaire did not include questions about the length of time children had been in a multilingual environment. Travis et al. do not report the distribution of ages across grades but note that the grades spanned kindergarten through sixth grade. They further state that the sample included a group (the "Opportunity group") they describe as a "group for mentally retarded children." Age 17 is unusually old for 6th grade. The practice of placing English Language Learners in lower grades is one possible reason for this. Another possibility is that the oldest children surveyed were in the "Opportunity group." All children were asked to read "[g]raded readable selections containing the most frequently used sounds" (Travis et al., 1937, p. 187) and were interviewed by the third author of the study, Jayne Shover. Children who did not speak English were asked to read passages translated into their native languages and were interviewed by interpreters. Travis et al. themselves pointed out that low language proficiency would result in disfluent speech in just about anyone and that differences in socioeconomic status could be responsible for differences between the groups. A number of authors have pointed out flaws in Travis et al. (1937)'s methods. For example, the criteria for stuttering and bilingualism were unstated (Byrd et al., 2016); the diagnosis was based on a single assessment (Shenker, 2004; Van Borsel, 2011; Van Borsel et al., 2001); and, for languages other than English, the diagnosis was not made by a trained clinician (Byrd et al., 2016; Van Borsel, 2011). It has also been pointed out that some of the prevalence estimates would seem to undermine the claimed causal connection between bilingualism and stuttering: Bloodstein and Bernstein Ratner (2008) credit Kathryn Kohnert for pointing out that the prevalence for trilinguals was lower (2.4%) than for bilinguals (2.8%) and higher (7.4%) for children who were monolingual in a language other than English. Along similar lines, Schneider (2015) points out that the prevalence for the African American children (given as 3.76%) exceeds that of the bilingual group; one might take this as an additional indication that the diagnoses were inaccurate, in light of the fact that there is no evidence to suggest that the prevalence of stuttering is higher in African American children (Proctor et al., 2008). One might add that Shover interviewed around 145 children a day (assuming a five-day school week over six and a half weeks, the stated duration of the study), a pace that precludes careful procedures. In sum, the accuracy of the stuttering diagnosis is questionable at best. Travis et al. (1937)'s Results Figure 1 depicts Travis et al. (1937)'s table showing the proportion of children who stuttered in each subgroup, along with annotations by the present author. The oft-cited prevalence rates of 1.8% for monolingual English-speakers ("English Speaking Only") and 2.8% for children who spoke English and one other language ("Bilingual") appear in the two leftmost cells in the final row of the table. The annotations in Figure 1 illustrate the method used here for reconstructing the absolute counts of children in each subgroup, by combining information from the main text with the percentages in the table. For a complete guide to the calculations, the reader is referred to Items 1–7 in Section 3 of Supplemental Material S12. Figure 1. Travis et al. (1937)'s results, annotated by the present author. The table as originally published is depicted in the broken line rectangle. Travis et al. (1937) table is Copyright © 1937 American Speech-Language-Hearing Association. Download figure Download PowerPoint Some of the counts can be reconstructed easily. For example, Travis et al. (1937) state that there were 10 boys who did not speak any English and that the stuttering prevalence in that group was 10% (cf. Items a and b in Figure 1). It follows that one boy in the group stuttered. One may find percentages for such small samples misleading, but the calculation is unassailably correct. The prevalence of 2.80% among the bilingual children (cf. Items c and d in Figure 1 and Item 1 in Supplemental Material S1) is also consistent with other information in the text: Travis et al. mention that there were 2,322 bilingual children. Indeed, 2.80% of 2,322 is 65.016, and 65 out of 2,322 is 2.799, which rounds to 2.80%, matching the reported results. Upon closer inspection, inconsistencies emerge. Here, we primarily focus on the monolingual English-speaking and bilingual groups. Notes on additional contradictions can be found in Supplemental Material S1. First, there is a discrepancy between the total reported sample size (4,827) and the sum of the subgroups, which is 4,837 (cf. Item 4 in Supplemental Material S1). A clerical error might be a reasonable explanation, as 4,827 and 4,837 differ in a single numerical digit. A second discrepancy reveals a major problem, however. It concerns the children classified as stuttering: The reported counts of English-Only (43), Bilingual (65), Trilingual (2), and Foreign-Only (2) sum to 112 (cf. Item 5 in Supplemental Material S1). But Travis et al. (1937) state that a total of 126 children stuttered. The figure 126 has additional support from the table, in that it matches the reported overall prevalence of 2.61% (assuming a sample size of 4,827). Short of assuming a complex set of typos in the table and in the text, the only way to reconcile the information is to conclude that 14 of the 126 children who stuttered were not included in any of the reported subgroups. Were these 14 children monolingual or bilingual? For a complete step-by-step guide to answering this question, the reader is referred to Items 6 and 7 in Supplemental Material S1. Here, we summarize the argument briefly: The key to the discrepancy can be found in the numbers of boys versus girls who participated in the study. From Travis et al.'s (1937) text, it is possible to reconstruct the number of boys (1,213) and girls (1,205), yielding a total of 2,418 monolingual English-speaking children—19 more than the reported total of 2,399 for that group (cf. Item 7 in Supplemental Material S1). This suggests that 19 children were excluded from the count of the monolingual English group: 14 who stuttered (as per Item 5 in Supplemental Material S1) and five who did not. If this is correct, then these 19 children were included in the sex-specific prevalence rates and in the count of children who stuttered, but excluded from the calculation of the stuttering prevalence among the English-only group. There is a third discrepancy, described in Item 3 of Supplemental Material S1. Briefly, there is reason to believe that the stuttering prevalence for the trilingual children was determined after excluding three fluent children, increasing the proportion of children who stuttered in that group. Travis et al. (1937) do not mention excluding any participants. It is conceivable that the 19 excluded cases were in the above-mentioned "Opportunity group." We cannot be sure of this, as the number of children in that group, their language backgrounds, and fluency status are unstated. In any case, it appears that the prevalence for the monolingual group was determined after excluding 14 stuttering and 5 fluent children from the monolingual English-speaking group, lowering the proportion of children who stuttered in that group. There is also reason to think that the proportion of children who stuttered in the trilingual group was increased by excluding several fluent cases before calculating the prevalence. Excluding monolingual stuttering children and trilingual fluent ones shifts the prevalence estimates so as to increase the impression of a causal link between multilingualism and stuttering. The Robustness of Travis et al. (1937)'s Statistical Tests Excluding 19 (or 24, if we consider the trilingual group) out of almost 5,000 children may have seemed innocuous to Travis et al. (1937). Would the findings have been statistically significant if the 19 missing cases had been included in the monolingual English group? The answer is no. When the 19 excluded cases are included, the difference (which is now between 2.36%, i.e., 57 out of 2,418; vs. 2.80%, i.e., 65 out of 2,322) does not reach significance by a Chi-square test without Yates' correction, the test likely used by Travis and colleagues, χ2(1) = 0.649, p = .42. We next ask whether the statistical significance of the results was robust to small changes in stuttering diagnosis or language background. To answer this question, we simulated the process of re-assigning one child at a time from one fluency group to the other, tracking the associated p values. The full results are shown in Table S1 in Supplemental Material S1. It will be observed that moving a single child in the total group of 2,399 monolingual children from "fluent" to "stuttering" shifts the p value from .021 to .027. Reassigning two children within the monolingual group and two within the bilingual group suffices to push the p value past the .05 level of significance. Thus, changes in group sizes far smaller than the discrepancies we noted in the previous section affect the statistical significance of the results. Travis et al. (1937)'s Influence Given the age of Travis et al. (1937)'s study and its many acknowledged flaws, one might expect its influence to be limited at this point. That is not the case. Literature reviews have repeatedly pointed out the scarcity of studies comparing stuttering prevalence among monolingual versus bilingual children (or adults) and the inconclusiveness of the extant literature. Pooling all combinations of languages together, reviews by Van Borsel (2011), Choo and Smith (2020), and Werle et al. (2019) mention a total of four group studies since 1937 reporting higher stuttering prevalence in bilingual or bidialectal versus monolingual children (Firozjaei, 2013; Howell et al., 2009; Ralston, 1981; Stern, 1948), along with five others reporting no significant effect of bilingualism per se (Aron, 1962; Au-Yeung et al., 2000; McLeod et al., 2014; Mohamadi et al., 2008; Ralston, 1976). Some of these studies have elicited disagreement (see, e.g., Packman et al., 2009's response to Howell et al., 2009). The low number of relevant reports and the seemingly compelling results in Travis et al. (1937) may partly explain why the study has been cited so frequently and why it continues to be cited. Another reason for the position of the study in the literature may be that it meshes well with some proposals about stuttering etiology. A full discussion of the links between Travis et al. (1937) and subsequent theories falls outside the scope of this commentary. However, as pointed out in Shenker (2011), the clinical recommendation (no longer made by ASHA but still very much alive, if anecdotal reports are any indication) to avoid or delay exposure to a second language in children considered at risk of stuttering is rooted in the idea that multilingualism might cause excessive demands on the developing system. As Shenker (2011) also points out, excessive demands on the linguistic system have in turn been held to cause disfluencies under the Demands and Capacities Model (see, e.g., Adams, 1990), a model that has been influential in clinical practice (see, e.g., Bernstein Ratner, 2000; Packman et al., 2004; and Shenker, 2004, for discussion). Concluding Remarks The Travis et al. (1937) study has had an enormous influence on the literature about the intersection of bilingualism and stuttering. Gauging its impact on clinical practice is difficult. What is clear is that the study plays into a still-prevalent notion that has informed clinical and educational practice and policy that bilingualism might hinder children's development in some way. Travis et al. (p. 189) comment that the difference between 1.8% and 2.8% "is really quite small" and that "[i]t is not to be overlooked that 97.20 per cent of the bilinguals do not stutter." But parents and clinicians may not actually consider the difference to be small: 1.8% represents a substantial decrease (of 36%!) over 2.8%. Parents may be eager to eliminate any avoidable risk factor, despite the negative consequences of heritage language loss and the positive consequences of strong heritage language proficiency (see, e.g., Lee & Suarez, 2009; Oh & Fuligni, 2010; Wong Fillmore, 2000). It is therefore important to realize that the purported effect of bilingualism on stuttering in the Travis et al. study was not just small, but apparently unsupported by the data in the first place. Supplemental Material on Figshare Acknowledgments I thank Yusuf Ali for drawing my attention to Travis et al. (1937) in the course of working on his UC Berkeley Honors Thesis, which caused me to sit down and read the study, Lily Wong Fillmore for her encouraging comments on an earlier version of this work. References Adams, M. R. (1990). The demands and capacities model I: Theoretical elaborations.Journal of Fluency Disorders, 15(3), 135–141. https://doi.org/10.1016/0094-730X(90)90014-J CrossrefGoogle Scholar Aron, M. L. (1962). The nature and incidence of stuttering among a Bantu group of school-going children.Journal of Speech and Hearing Disorders, 27(2), 116–128. https://doi.org/10.1044/jshd.2702.116 LinkGoogle Scholar Au-Yeung, J., Howell, P., Davis, S., Charles, N., & Sackin, S. (2000). UCL survey of bilingualism and stuttering.Journal of Fluency Disorders, 25(3), 246. https://doi.org/10.1016/S0094-730X(00)80321-6 CrossrefGoogle Scholar Bernstein Ratner, N. (2000). Performance or capacity, the model still requires definitions and boundaries it doesn't have.Journal of Fluency Disorders, 25(4), 337–346. https://doi.org/10.1016/S0094-730X(00)00083-8 CrossrefGoogle Scholar Bloodstein, O., & Bernstein Ratner, N. (2008). A handbook of stuttering. Thomson Delmar Learning. Google Scholar Byrd, C. T., Haque, A. N., & Johnson, K. (2016). Speech-language pathologists' perception of bilingualism as a risk factor for stuttering.Journal of Communication Disorders, Deaf Studies & Hearing Aids, 4(2), Article 158. https://doi.org/10.4172/2375-4427.1000158 CrossrefGoogle Scholar Choo, A. L., & Smith, S. A. (2020). Bilingual children who stutter: Convergence, gaps and directions for research.Journal of Fluency Disorders, 63, Article 105741. https://doi.org/10.1016/j.jfludis.2019.105741 CrossrefMedlineGoogle Scholar Firozjaei, A. K. (2013). Prevalence of stuttering in bilingual and monolingual primary schools.International Research Journal of Applied and Basic Sciences, 4(6), 1328–1331. Google Scholar Howell, P., Davis, S., & Williams, R. (2009). The effects of bilingualism on stuttering during late childhood.Archives of Disease in Childhood, 94(1), 42–46. https://doi.org/10.1136/adc.2007.134114 CrossrefMedlineGoogle Scholar Lee, J. S., & Suarez, D. (2009). A synthesis of the roles of heritage languages in the lives of children of immigrants: What educators need to know.In T. G. Wiley, J. S. Lee, & R. W. Rumberger (Eds.), The education of language minority immigrants in the United States (pp. 136–171). Multilingual Matters. Google Scholar McLeod, S., Verdon, S., & Kneebone, L. B. (2014). Celebrating young Indigenous Australian children's speech and language competence.Early Childhood Research Quarterly, 29(2), 118–131. https://doi.org/10.1016/j.ecresq.2013.11.003 CrossrefGoogle Scholar Mohamadi, H., Nilipour, R., & Yadegari, F. (2008). Stuttering prevalence among Kurdish-Farsi students: Effects of the two languages similarities.Iranian Rehabilitation Journal, 6(1), 83–88. http://irj.uswr.ac.ir/article-1-80-en.html Google Scholar Oh, J. S., & Fuligni, A. J. (2010). The role of heritage language development in the ethnic identity and family relationships of adolescents from immigrant backgrounds.Social Development, 19(1), 202–220. https://doi.org/10.1111/j.1467-9507.2008.00530.x CrossrefGoogle Scholar Packman, A., Onslow, M., & Attanasio, J. (2004). The demands and capacities model: Implications for evidence-based practice in the treatment of early stuttering.In A. Bothe (Ed.), Evidence-based treatment of stuttering (pp. 65–79). Erlbaum. Google Scholar Packman, A., Onslow, M., Reilly, S., Attanasio, J., & Shenker, R. (2009). Stuttering and bilingualism.Archives of Disease in Childhood, 94(3), 248. MedlineGoogle Scholar Proctor, A., Yairi, E., Duff, M. C., & Zhang, J. (2008). Prevalence of stuttering in African American preschoolers.Journal of Speech, Language, and Hearing Research, 51(6), 1465–1479. https://doi.org/10.1044/1092-4388(2008/07-0057) LinkGoogle Scholar Ralston, L. D. (1976). Stammering: A possible result of language interference in a bi-dialectal community, Nevis, West Indies. Paper presented to the Society for Caribbean Linguistics. Google Scholar Ralston, L. D. (1981). Stammering: A stress index in Caribbean classrooms.Journal of Fluency Disorders, 6(2), 119–133. https://doi.org/10.1016/0094-730X(81)90010-3 CrossrefGoogle Scholar Schneider, S. (2015). Bilingualer Erstspracherwerb: Zweisprachig von Anfang an. UTB. CrossrefGoogle Scholar Shenker, R. C. (2004). Bilingualism in early stuttering: Empirical issues and clinical implications.In A. Bothe (Ed.), Evidence-based treatment of stuttering (pp. 81–96). Erlbaum. Google Scholar Shenker, R. C. (2011). Multilingual children who stutter: Clinical issues.Journal of Fluency Disorders, 36(3), 186–193. https://doi.org/10.1016/j.jfludis.2011.04.001 CrossrefMedlineGoogle Scholar Stern, E. (1948). A preliminary study of bilingualism and stuttering in four Johannesburg schools.South African Journal of Communication Disorders, 1(1), 15–24. Google Scholar Szmalec, A. (2013). Bilinguisme et bégaiement chez l'enfant.Enfance, 3, 287–298. CrossrefGoogle Scholar Travis, L. E., Johnson, W., & Shover, J. (1937). The relation of bilingualism to stuttering: A survey of the East Chicago, Indiana, schools.Journal of Speech Disorders, 2(3), 185–189. https://doi.org/10.1044/jshd.0203.185 LinkGoogle Scholar Van Borsel, J. (2011). Review of research on the relationship between bilingualism and stuttering.In P. Howell & J. Van Borsel (Eds.), Multilingual aspects of fluency disorders (pp. 247–270). Multilingual Matters. CrossrefGoogle Scholar Van Borsel, J., Maes, E., & Foulon, S. (2001). Stuttering and bilingualism: A review.Journal of Fluency Disorders, 26(3), 179–205. https://doi.org/10.1016/S0094-730X(01)00098-5 CrossrefGoogle Scholar Werle, D. R., Byrd, C., & Coalson, G. (2019). Description of multilingual participants who stutter: An update 2011–2018.Communication Disorders Quarterly. Advance online publication. https://doi.org/10.1177/1525740119870772 CrossrefGoogle Scholar Wong Fillmore, L. (2000). Loss of family languages: Should educators be concerned?.Theory Into Practice, 39(4), 203–210. https://www.jstor.org/stable/1477339 CrossrefGoogle Scholar Yairi, E., & Ambrose, N. (2013). Epidemiology of stuttering: 21st century advances.Journal of Fluency Disorders, 38(2), 66–87. https://doi.org/10.1016/j.jfludis.2012.11.002 CrossrefMedlineGoogle Scholar Footnote 1As noted by others (e.g., Byrd et al., 2016), whether these children actually stuttered is not clear, particularly as Travis et al. (1937) did not specify the diagnostic criteria they used. Several facts about the reported numbers suggest that the stuttering diagnosis was likely unwarranted in many cases. Nevertheless, given that Travis et al. considered these children to be diagnosed with stuttering, they will be referred to as such in this article. 2Supplemental Material: https://doi.org/10.23641/asha.12986066 Author Notes Disclosure: The author has declared that no competing interests existed at the time of publication. Correspondence to Susanne Gahl: [email protected] Editor-in-Chief: Bharath Chandrasekaran Editor: Julie D. Anderson Additional Resources FiguresReferencesRelatedDetails Volume 63Issue 11November 2020Pages: 3680-3684 HistoryReceived: Jun 26, 2020Revised: Aug 3, 2020Accepted: Aug 11, 2020 Published online: Sep 25, 2020 Published in issue: Nov 13, 2020PubMed ID: 32976049 Get Permissions Add to your Mendeley library Metrics Downloaded 3,217 times Topicsasha-topicsasha-article-typesCopyright & PermissionsCopyright © 2020 The AuthorLicensesThis work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.PDF DownloadLoading ...