Why not both? Rethinking categorical and continuous approaches to bilingualism

Abstract

Bilingualism is a complex construct, and it can be difficult to define and model. This paper proposes that the field of bilingualism can draw from other fields of psychology, by integrating advanced psychometric models that incorporate both categorical and continuous properties. These models can unify the widespread use of bilingual and monolingual groups that exist in the literature with recent proposals that bilingualism should be viewed as a continuous variable. In the paper, we highlight two models of potential interest: the factor mixture model and the grade-of-membership model. These models simultaneously allow for the formation of different categories of speakers and for variation to exist within these categories. Researchers can then conduct their analyses on either the categorical or continuous information, or a combination of the two, depending on which is most appropriate to address their research question. Conceptualizing bilingualism within the context of these more flexible models will help to advance theory and lead to a fuller and deeper understanding of bilingualism.

Different measurements of bilingualism and their effect on performance on a Simon task

“…Third, although there is a movement toward treating bilingualism as a continuous variable that is endorsed by many (e.g., Champoux-Larsson & Dylman, 2019;DeLuca et al, 2019;Edwards, 2012;Gullifer et al, 2018;Gullifer & Titone, 2020;Incera & McLennan, 2018;Jylkkä et al, 2017;Kaushanskaya & Prior, 2015;Luk & Bialystok, 2013;Sulpizio et al, 2020;Surrain & Luk, 2019), as Kremin and Byers-Heinlein (2020) point out, there are situations where this may not be possible or preferable (e.g., with small samples). Therefore, giving up a dichotomous classification of bilingualism altogether may not be the answer when it comes to operationalizing bilingualism (Kremin & Byers-Heinlein, 2020). Using a factor mixture model or a grade-of-membership model, which allow for categorization but considers the variation within the categories, would allow analysing results based on categories, on a continuous scale, or even on both (Kremin & Byers-Heinlein, 2020).…”

“…Therefore, giving up a dichotomous classification of bilingualism altogether may not be the answer when it comes to operationalizing bilingualism (Kremin & Byers-Heinlein, 2020). Using a factor mixture model or a grade-of-membership model, which allow for categorization but considers the variation within the categories, would allow analysing results based on categories, on a continuous scale, or even on both (Kremin & Byers-Heinlein, 2020). The flexibility that such models provide would allow choosing an approach that would be driven by the research question, by the latent concept that is analyzed, and by the sample.…”

“…However, few people are either monolingual or bilingual, but rather, most fall somewhere on a range in between the two extremes. Thus, it is increasingly argued that bilingualism should be operationalized as a continuous variable in order to better reflect its true nature and thus increase the precision and sensitivity of the operationalization (e.g., Champoux-Larsson & Dylman, 2019;DeLuca, Rothman, Bialystok, & Pliatsikas, 2019;Edwards, 2012;Gullifer et al, 2018;Gullifer & Titone, 2020;Incera & McLennan, 2018;Jylkkä et al, 2017;Kaushanskaya & Prior, 2015;Luk & Bialystok, 2013;Sulpizio, Del Maschio, Del Mauro, Fedeli, & Abutalebi, 2020;Surrain & Luk, 2019, but see Kremin & Byers-Heinlein, 2020, for a suggestion on how to use both categorical and continuous approaches simultaneously based on a factor mixture model and on a gradeof-membership model). Yet, there are no systematic investigations to determine whether this can directly affect the outcomes of studies.…”

A Review of questionnaires quantifying bilingual experience in children: Do we document the same constructs?

“…Our aim is not to argue for or against the use of composite measures -such as language entropy (Gullifer & Titone, 2020) or the continuous factor score method advocated by Anderson et al (2018). Furthermore, while acknowledging the multi-dimensional nature of bilingualism, our purpose is not to discuss the relative importance of each dimensionsuch as language proficiency (Hulstijn, 2012) or child-level and context-level variables (Byers-Heinlein, Esposito, et al, 2019), nor to argue about the relative merits or the comparability of categorical vs. continuous approaches to bilingualism (Kremin & Byers-Heinlein, 2020). Rather, we will focus on the raw measures used to operationalise bilingualism in order to:…”

“…Some recent opinion papers have tried to provide reasons for the conflicting results and suggested that diverging approaches to the multidimensional nature of bilingualism might be partly responsible for the lack of replicability in findings (Valian, 2015;Bak, 2016). Marian and Hayakawa (2020) and Kremin and Byers-Heinlein (2020) have convincingly argued that bilingualism research would benefit from greater transparency regarding the measures used to operationalise the variables of interest.…”