Shared Lexical Items as Triggers of Code Switching (2023)

Abstract: Why do bilingual speakers code-switch (mix their two languages)? Among the several theories that attempt to explain this natural and ubiquitous phenomenon, the triggering hypothesis relates code-switching to the presence of lexical triggers, specifically cognates and proper names, adjacent to the switch point. We provide a fuller, more nuanced and refined exploration of the triggering hypothesis, based on five large datasets in three language pairs, reflecting both spoken and written bilingual interactions. Our results show that words that are assumed to reside in a mental lexicon shared by both languages indeed trigger code-switching, that the tendency to switch depends on the distance of the trigger from the switch point and on whether the trigger precedes or succeeds the switch, but not on the etymology of the trigger words. We thus provide strong, robust, evidence-based confirmation to several hypotheses on the relationships between lexical triggers and code-switching.

## introduction more than half the world's population today is multilingual, yet our understanding of the underlying linguistic and cognitive principles that govern multilingual language is imperfect. it is largely based on controlled laboratory studies, and only recently have psycholinguists begun exploring the extent to which insights from laboratory experiments can be applied in a real-world, communicative setting @xcite . lacking firm theoretical underpinnings, contemporary language technology often does not reflect the ubiquity of multilingual communication. we focus in this paper on code-switching (cs), the natural tendency of bilingual speakers conversing with each other to switch between two languages, sometimes within a single utterance or even a single word. our main goal is to explore a specific hypothesis related to cs, namely, that certain words tend to trigger cs more than others. the main contribution of this work is theoretical, but we trust that its results will be instrumental for improving future multilingual nlp applications. several competing theories try to explain cs, and in particular to identify the factors that contribute to the (typically unconscious) decision of a speaker to code-switch. speakers are conjectured to code-switch when the concept they are about to utter is more accessible in the other language @xcite ; or more specific, lacking precise enough words in the current language @xcite ; or carrying a major information load, so that the switch signals to the listener that an important concept is introduced @xcite . the tendency to code-switch is influenced by linguistic factors (e.g., cognates are assumed to trigger cs), socio-linguistic factors (e.g., the fluency of the interlocutors in each of the two languages), demographic ones (e.g., the age, gender, or provenance of dialogue participants), and more @xcite @xcite . we focus on the triggering hypothesis, whereby ''lexical items that can be identified as being part of more than one language for the speaker [...] may facilitate a transversion from one language to another'' @xcite . this hypothesis was explored extensively in the past, but earlier studies were limited in scope, were based on limited data, and addressed only spoken language. this work makes several contributions. first, we investigate a specific type of lexical trigger: we define a category of lexical items (mainly proper names and culturally specific terms) that we expect to reside in more than one (or alternatively, in a shared) mental lexicon (section 3). we also pay attention to whether such items originate in one of the two languages or in a third language. second, unlike previous work, which dealt exclusively with spoken data, we investigate both spoken and written data, in five large datasets that include cs in three language pairs: english-spanish, english-german, and english-arabic foot_0 (section 4). third, while we employ the same statistical test that has been used by previous works to assess the association between such shared items and cs, we augment the analysis by also quantifying the magnitude of this association as an indication of the strength of the phenomena we observe (section 5), thereby adding statistical rigor to our analysis. our results (section 6) show strong associations between the presence of shared items (the type of trigger we focus on) and the tendency to code-switch, in all language pairs and datasets. we also provide a thorough and nuanced analysis (section 7) of the location of the shared item with respect to the switch point, showing that the tendency to switch is lower when the trigger is adjacent to the switch rather than precedes it, and that the association between triggers and cs diminishes as the shared items are more distant from the switch point. overall, we provide a much fuller, more nuanced picture of the relationships between lexical triggers and cs than was available so far. foot_1 2 related work multilinguality is becoming more and more ubiquitous, to the extent that psycholinguists increasingly acknowledge that bilingualism is the rule and not the exception @xcite . grosjean (2010, page 16) stated that ''bilingualism is a worldwide phenomenon, found on all continents and in the majority of the countries of the world @xcite assessed that more than half the world's population today is multilingual. monolingual and multilingual speakers alike seamlessly adjust their communication style to their interlocutors @xcite @xcite @xcite . specifically, when interlocutors share more than one language, they almost inevitably engage in cs @xcite @xcite . most linguistic research on cs has focused on spoken language @xcite @xcite . however, with the rise of social media, written cs @xcite has become a pervasive communication style @xcite . the spoken language domain is not directly comparable to the written one, and findings on cs in written conversations differ somewhat from those in speech @xcite @xcite . the work we present here addresses both modalities. various competing theories attempt to explain cs, or at least to propose factors that contribute to the tendency of bilingual speakers to codeswitch. notable among them is the triggering hypothesis, which states that specific lexical items that may be included in more than one mental lexicon for the speaker trigger switching @xcite . such lexical items include, according to clyne, lexical transfers (i.e., borrowed words and expressions), bilingual homophones (including loans from a third language), and proper nouns. in this work we focus on a specific type of potential triggers, consisting mainly of proper names but including also culturally specific lexical items that originate in one language and do not have a readily available translation in the other language (e.g., 'taco', originally from spanish, in english-spanish dialogues, or 'muezzin', originally from arabic, in english-arabic conversations). the triggering hypothesis was explored extensively by @xcite @xcite , but these early investigations did not include any statistical analysis. this was first introduced by @xcite , who worked with ''a series of transcribed conversations between three dutch-moroccan arabic bilinguals''. this dataset was extremely small by modern standards (it included a few dozen switch points and a few dozen potential triggers). similarly, @xcite based her entire analysis on a single 24-minute interview with a single (dutch-english speaking) informant. still, both were able to find statistically significant associations between triggering and cs. more recently, @xcite extended this investigation to a larger corpus (the bangor-miami corpus of spanish-english @xcite ), but focused only on a predefined list of cognates that they collected. in contrast, we work with much larger datasets that include thousands of switch points and potential triggers, in three different language pairs, and with both spoken dialogues and written socialmedia interactions. @xcite (and, subsequently, also @xcite and @xcite ) used the χ 2 test to measure the correspondence between triggering and cs. we use the same measure (more precisely, fisher's exact test, whose significance does not rely on an approximation that is only exact in the limit); but we extend the analysis by considering not only the statistical significance of the test, as determined by its p-value, but also the magnitude of the association between categories as an indication of the strength of the phenomena we observe, as determined by relative risk (also known as risk ratio). this facilitates a much more nuanced analysis of the results. ## goals our main goal in this work is to explore the triggering hypothesis more closely, focusing on a class of lexical items that we expect to be shared across the multiple mental lexicons of the multilingual speaker. extending previous research, we aim at addressing the association between such shared items and cs in multiple datasets reflecting three different language pairs (en-ar, en-de, and en-es) foot_2 and two different modalities (spoken and written). ## analysis association between shared items and cs. our first hypothesis was that shared items are indeed associated with cs. to assess the association, we expect the fisher test to yield a statistically significant result in each of the statistical tests (i.e., no black diamonds in the plots). not surprisingly, we do find such association. recall that each plot (such as the one in figure 1 ) depicts the results of 36 tests, and that we have 20 such plots. of the 720 statistical tests, only 10 (1.4%) yield p-values greater than 0.05. we thus overwhelmingly establish the hypothesis that in all our datasets there is significant association between shared items of all kinds and cs, even when the shared item is as far as 6 tokens away from the cs point, and even when the shared item is adjacent to (i.e., may succeed) the cs point. it is interesting to note that of the 10 exceptions, 8 are in the denglisch corpus. we return to this below. the impact of the distance between shared items and the cs point. our second hypothesis was that the magnitude of the association diminishes as the shared item and the cs point are more distant. to confirm this hypothesis we need to show that the lines in the plots are decreasing, or at least non-increasing. this is indeed the case for 98 (82%) out of the 120 lines (6 per plot). furthermore, most of the lines that are not decreasing include only a single point that violates the hypothesized trend. the main issue is, again, with the de-en dataset, which is responsible for 13 out of the 22 exceptions. ## conclusion we investigated the triggering hypothesis using five datasets that reflect bilingual interactions in three language pairs. employing standard yet powerful statistical methodology, we strongly confirmed three hypotheses: (1) that there is a strong association between code-switching and shared lexical items (proper names, but also culturally specific items that may lack translation equivalents in the other language); (2) that this association is stronger when the shared item precedes the switch point, rather than neighbors it; and (3) that the association diminishes as the shared item is farther away from the cs point. we were unable to confirm a fourth hypothesis, namely, that shared items originating in language l 1 are more likely to trigger a switch from l 2 to l 1 than the other way round. we do not know whether this is due to noise in our datasets or a bona fide property of bilingual language, rooted in cognitive-theoretical explanations; we leave this for future investigation. while the data used to establish the above results are unprecedented in terms of their size and diversity, at least in the psycholinguistic literature, we believe that they do not tell a full story. we would very much like to extend our datasets to more language pairs, to have sufficiently large datasets that would facilitate a comparative analysis of spoken vs. written data, and also enough data to compare cs between etymologically close languages vs. unrelated language pairs. we leave such investigations for future research.