Predictability Effects of S panish- E nglish Code-Switching: A Directionality and Part of Speech Analysis (2025)

Abstract: Research on code-switching (CS), the spontaneous alternation between two or more languages within a discourse, remains relatively new and often limited by the use of elicited production tasks, with some exceptions leveraging naturalistic corpora. This study analyses the effects of language directionality and part-of-speech (POS) tags on Spanish-English CS production between corpus modalities and speech communities. We use data from two spoken corpora: Miami Bangor Corpus (MBC; N = 261,711) and Spanish in Texas Corpus (STC; N = 416,784), as well as the written LinCE Corpus (N=278,093). Bootstrap analyses indicate that Spanish serves as the matrix language (i.e., the most used) for MBC and LinCE, while English is for STC. Logistic regression analyses show that the particle-coordinating conjunction combination was the strongest POS predictor of a CS. The results suggest that corpus modality and the speech community affect matrix language proportions and that both previously attested and unseen POS combinations modulate the production of Spanish-English CS.

## introduction code-switching (cs), or the fluid switching between languages in bilingual speech or text @xcite , is ubiquitous in bilingual communities. this language alternation is known to be structured yet spontaneous @xcite , as it is believed that two (or more) languages are active in the speaker's brain @xcite . cs is categorized as inter-sentential (e.g., "no saldré hoy [i am not going out today]. i'm too tired.") or intra-sentential (e.g., "she bought una casa en florida [a house in florida]"). since languages are not used with the same frequency, the most dominant is considered the matrix language, strongly influencing the morphosyntactic structure of the discourse @xcite . previous research has identified several characteristics of cs. for example, the presence of cognates seems to trigger a language switch @xcite , and the pos combination of determiner-noun has been noted as a frequent point of switch @xcite . specifically in the case of spanish-english cs, there is evidence suggesting that spanish often serves as the matrix language in cs @xcite , and, regardless of this matrix, there is a consistent pattern where a spanish determiner is followed by an english noun (e.g. la house) @xcite . however, these studies mainly rely on (small) sets of controlled stimuli from psycholinguistic experimentation (cf. @xcite ; @xcite ), lacking analysis of naturalistic data (e.g., corpora), meaning that it is unclear whether the mentioned patterns are present in naturalistic cs speech. our work addresses these limitations. leveraging three spanish-english cs corpora covering both spoken and written modalities, we ask: (1) to what degree is cs production constrained by the language directionality (i.e., spanish-english vs. english-spanish) of the cs? ( 2 ) to what degree can the pos combination of a pair of words predict whether a cs occurs between those words? (3) if directionality and pos effects are found, are these findings modulated by corpus modality (oral vs. written) and speech community? given that spanish tends to occur as the matrix language in spanish-english cs @xcite , we predict that spanish-english cs occurs at higher proportions than in the opposite direction. we also predict that particular poss will be able to predict the occurrence of cs, specifically with determiners (dets, among other tags) occurring as the first word in a bigram containing a cs @xcite and conjunctions (conj) occurring as the second word in a bigram containing a cs @xcite . it is difficult to hypothesize the answers to the third question, since there is a lack of literature on spanish-english cs in the written domain, and also that the effect of speech community on cs has been generally neglected @xcite . regarding the effect of corpus modality on cs production, it might not be surprising to see differences in matrix language selection between oral and written corpora, taking into account various differences (including register variations) between modalities @xcite . in one of the few studies examining the effects of speech community on spanish-english cs, @xcite compared determiner-noun (det-n) cs production in the miami bangor corpus (mbc) to a corpus of interviews conducted in nicaragua. the authors found significantly higher rates of spanish-english det-n css in the mbc, while english-spanish det-n rates were higher in the nicaragua corpus @xcite . as such, we conjecture that differences in regional norms may manifest in directionality effects. for example, spanish-english cs may occur at higher rates in the mbc than the spanish-english proportions of the spanish texas corpus (stc), since spanish has been documented as the matrix language in spanish-english cs in the mbc @xcite , but not in stc. ## related work recent experiments have used computational analyses of linguistic corpora to uncover spanish-english cs trends @xcite , but they face limitations in two respects. first, most experiments focus on modeling distributional trends in cs (e.g., the preference for the estar + english gerund switch @xcite ) or improving a model's ability to diagnose the presence of a cs @xcite through semi-supervised language identification methods that leverage monolingual data and models like viterbi decoding. second, much of the corpus-based research on spanish-english cs is limited to one corpus, such as the mbc @xcite or the stc @xcite , raising the question of whether the trends discovered would be representative of those across speech modalities and communities. furthermore, given that non-computational analyses have found regional differences in det-n cs patterns, it stands to reason that these differences would appear in cs behavior @xcite . however, this analysis did not account for regional differences in other structural properties of spanish-english cs (e.g., other pos pairings or trends in matrix language usage). closer to this research, through a cross-linguistic analysis of spanish-english and mandarin-english corpora, @xcite highlight pos tags as strong predictors of cs and expand this idea by concluding that this predictive strength decreases the farther a word is from the cs point. while their study underscores the value of pos based approaches, their spanish-english analysis was also limited to the mbc. we extend overall previous research by comparing cs patterns in three corpora of different modalities, identifying a range of pos tag combinations that predict the presence or absence of cs, and testing prior assumptions about spanish as the default matrix language. we highlight the role of modality and speech community as key factors shaping cs behavior. ## discussion and limitation after analyzing three spanish-english spoken and written corpora, we expanded previously known patterns of directionality and pos in cs. bootstrapping showed a tendency in spanish-english switches throughout the mbc and lince corpora, while the opposite was found in the stc. the logistic regression analysis concluded a robust number of pos combinations that predicted cs: tags like intj and propn were commonly present during switches, while pron and sconj were not. this paper contributes to the field by highlighting the complex role that pos plays in spanish-english cs. similarly to @xcite , we found that a variety of tags predicts the event that precedes (intj, propn, noun and part, among others) or follows (intj, propn, part, cconj and sconj, among others) a given cs. phrases like example 1 in the fact that @xcite did not find predictive validity of the sconj and cconj tags following a cs but our experiment did, can be explained by a difference in the corpora analyzed. soto et al. (2018) examined solely a portion of the mbc, while our work covered two additional corpora, besides the entirety of mbc; the cs behavior in @xcite 's analyses may be qualitatively and quantitatively different from the data used in this study. moreover, a switch occurring before a cconj and sconj could be expected since these pos tags often introduce new clauses or sentencelike units, creating opportunities for a language switch (as seen in example 4, to our knowledge, this is the first research to empirically establish a higher proportion of english-spanish cs relative to spanish-english cs with the written stc corpus. this finding may be motivated by pragmatic differences in cs across written and oral corpora. however, it could also be the case that speech community and corpus modality combine to affect distributional trends of spanish-english and english-spanish cs. further investigation of this would require more written spanish corpora, which is lacking at the moment; however, we hope that future work can mitigate this gap. despite the implications of this study, it is not without limitations. first, only three corpora were analyzed due to the lack of more publicly available data. we look forward to expanding our experiments to additional speech communities in the future. second, we only examined spanish-english cs, two languages considered relatively high-resource; we hope that our analyses can be extended to different language pairings, particularly those that involve understudied languages, to probe the generalizability of our findings. one final limitation of our analyses is that we used pos tags and not dependency relations to investigate spanish-english cs. our decision, which is line with with previous cs research (i.e. @xcite , @xcite , inter alia), was motivated by the fact that pos tags are (albeit a somewhat simplistic) way to gain information about structural characteristics of spanish-english cs. for example, our analyses provided novel insight into the predictability of intj, noun, and part occurring before a cs and intj, part, cconj, and sconj occurring after a cs. however, we recognize the value of including dependency relations in our analyzes, given that in german-english cs, two adjacent words have been reported to be more likely to be in the same language if they are more directly related in terms of dependency relations @xcite . we expect that future analyses consider both pos tags and dependency relations to further enrich the field's understanding of spanish-english cs.