M Carmen

Parafita Couto¹

Miriam Greidanus

Kate Bellamy²

Code-switching at the interface between language, culture, and cognition

Keywords: culture, and cognition, Lapurdum: Basque Studies Review

Bilinguals commonly draw on their two languages within a single speech event, a practice known as code-switching. On the basis of different methods and bilingual populations, various theoretical accounts of code-switching have been developed. Yet, while theories proliferate, cross-fertilization between them remains limited. Hence, the question that guides this paper is: how can we better understand the nature of mixed interactions, with a view to creating more accurate models of (multilingual) language competence? We show how a multimethod, comparative approach that integrates linguistic, psycholinguistic and social factors will help us draw a distinction between which codeswitching patterns are uniform across communities and language pairs, and which patterns are variable. Addressing both the nominal and verbal domains, we present findings from a series of comparative studies that investigate how bilinguals from different communities produce, judge, or process bilingual structures. We discuss to what extent bilinguals (i) produce strings that can be seen as having the same syntactic structure within and across communities, (ii) make the same linguistic judgments, and (iii) converge in their processing of these strings. We highlight the importance of surveying the patterns that emerge across communities, rather than on an example and counterexample basis, in order to bring our understanding of code-switching, and of language as a whole, forward.

Introduction: Challenges in evaluating code-switching theories

In this paper, we will reflect on the competing theoretical and methodological tensions in the structural study of code-switching (CS), that is, the multilingual practice where speakers "go back and forth" between their languages within the same a conversation, either between clauses (inter-clausal) or within the same clause (intra-clausal; [START_REF] Deuchar | Code-switching[END_REF]. An example of intra-clausal CS can be observed in the utterance produced by a Dutch-Portuguese bilingual in Brazil in (1). A Portuguese noun (italics) is inserted into an otherwise Dutch clause without signs of effort or hesitation.

(1) je moet echt een beejte criatividade hebben you must really INDEF little creativity have.INF 'You must really have a bit of creativity.' (Greidanus Romaneli, in prep.) The intra-clausal CS of a New York Puerto Rican Spanish-English bilingual was identified by Labov (1971: 457) as "the irregular mixture of two distinct systems". Nevertheless, by the end of the 1970s, structural constraints on CS were being proposed [START_REF] Pfaff | Constraints on language mixing: Intrasentential code-switching and borrowing in Spanish/English[END_REF], and today CS is widely accepted as rule-governed behavior, in other words there are boundaries in speech where it is allowed or disallowed. As such, CS data should be incorporated into any theory of possible mental grammars [START_REF] López | Toward an Integrated Model of Bilingual Grammar[END_REF]. Mixed language data is also valuable because it permits combinations of formal properties that are hidden in the examination of a single language (e.g., contrasting word order), helping us to refine and deepen our understanding of grammatical theory.

While numerous theories have been developed to explain CS structure, efforts to integrate empirical findings have met various theoretical and methodological challenges. Here, we briefly illustrate the spectrum of these theoretical approaches, highlighting two challenges hampering theoretical convergence in the field: the absence of community norms in theoretical models, and the difficulty of adjudicating between findings from different methodologies.

Theoretical approaches

Explanations of CS structure can be roughly divided into two groups: those that posit additional mechanisms to handle mixed language data, and those that do not (see Table 1 below for a non-exhaustive overview).

Table 1. Non-exhaustive overview of structural approaches to CS since the 1980s.

Approach

Government Constraint, 1986), and for functional heads and their components to come from the same language (Belazi, Rubin, & Toribio's Functional Head Constraint, 1994). However, evidence from different language pairs contradicting many of these constraints soon emerged [START_REF] Bentahila | The syntax of Arabic-French codeswitching[END_REF][START_REF] Berk-Seligson | Linguistic constraints on intrasentential code-switching: A study of Spanish/Hebrew bilingualism[END_REF][START_REF] Nartey | Code-switching, interference, or faddism? Language use among educated Ghanians[END_REF], leading to the later reformulation of these constraints [START_REF] Deuchar | Congruence and Welsh-English code-switching[END_REF][START_REF] Sebba | On the notions of congruence and convergence in code-switching[END_REF].

The constraint-based approach was also challenged by the "null" view that no structural restrictions should operate specifically on CS. Instead, proponents of this approach argue that CS should be explained -and explainable -using the same mechanisms applied to monolingual grammars (e.g., generativist proposals such as [START_REF] Mahootian | A Null Theory of Codeswitching[END_REF][START_REF] Macswan | A Minimalist Approach to Intrasentential Code-Switching[END_REF][START_REF] Macswan | The architecture of the bilingual language faculty: Evidence from intrasentential code switching[END_REF][START_REF] Chan | Aspects of the syntax, production, and pragmatics of codeswitching: with special reference to Cantonese-English[END_REF][START_REF] Alexiadou | Language mixing: A distributed morphology approach[END_REF][START_REF] López | Toward an Integrated Model of Bilingual Grammar[END_REF] cf. also [START_REF] Eppler | Word Grammar and syntactic code-mixing research[END_REF] using word grammar). Critics of these approaches have noted that they may not be suited to explain the creation of new code-switched structures not available in either of the individual languages, nor can they explain variation between speakers of the same language pair in different communities [START_REF] Toribio | Structural approaches to code-switching[END_REF].

The observation that many code-switched utterances feature an asymmetrical involvement of the participating languages led to the generation of the Matrix Language Framework (MLF;[START_REF] Myers-Scotton | Common and uncommon ground: Social and structural factors in codeswitching[END_REF][START_REF] Myers-Scotton | Contact linguistics: Bilingual encounters and grammatical outcomes[END_REF]; see also [START_REF] Joshi | Processing of sentences with intra-sentential code-switching[END_REF]. This account generalizes that in code-switched utterances one of the languages -the matrix languageprovides the morphosyntactic frame, while the other language -the embedded languagecontributes embedded elements. Moreover, the MLF predicts that only certain 'open class' items can be drawn from the embedded language (with the exception of embedded language "chunks"), whereas no such restriction applies to the matrix language. The requirement for one language to act as the matrix language also applies to unilingual speech, therefore the MLF is claimed not to require CS-specific constraints [START_REF] Jake | Making a minimalist approach to code-switching work: Adding the matrix language[END_REF]cf. MacSwan, 2005).

Others have attempted to reconcile structural explanations with the socio-pragmatic functions of CS (e.g. [START_REF] Chan | Code-switching between typologically distinct languages[END_REF] who highlights the role of processing and sociolinguistic factors). Most notable in this respect is [START_REF] Muysken | Bilingual Speech: A typology of code-mixing[END_REF][START_REF] Muysken | Language contact outcomes as the result of bilingual optimization strategies[END_REF] typology of codeswitching, which identifies four types of code-switching that reveal different levels of contribution from the two languages: insertion (of individual items), alternation (the juxtaposition of material from different languages), congruent lexicalization (denser types of code-switching with shared structures), and backflagging (the use of other-language clause-peripheral markers). In this account, a variety of factors that influence the particular outcome of each multilingual situation are elaborated, such as typological distance, political distance or community norms. In a similar vein, [START_REF] Bhatt | Code-switching and the optimal grammar of bilingual language use[END_REF] employed a framework of bilingual grammars based on Optimality Theory. They identified a repertoire of socio-pragmatic functions, such as display social affiliation or express a specific concept more economically, whose relative importance in a community could help predict preferred code-switched structures in bilingual communities. Finally, [START_REF] Backus | A usage-based approach to codeswitching: The need for reconciling structure and function[END_REF] proposed a usage-based analysis of code-switching structure, in which the pragmatic function of a specific linguistic form (e.g., words, schematic structures) and the frequency with which it is used in a community influences individual speakers' likelihood of producing this form. This way, CS is linked to other language contact phenomena, as a synchronic practice leading to language change over time.

More recently, Gradient Symbolic Computation, a formalism to account for the systematicity of CS patterns by integrating psycholinguistic notions of bilingual coactivation with generativist accounts of grammar, was proposed [START_REF] Goldrick | Coactivation in bilingual grammars: A computational account of code mixing[END_REF][START_REF] Putnam | The good, the bad, and the gradient: The role of losers in code-switching[END_REF].

A continued lack of convergence between these varying theoretical approaches has been characterized as demonstrating "little cross-fertilization" between CS theories [START_REF] Poplack | Code-switching (linguistic)[END_REF](Poplack, : 2063)), leading to a situation where a "culture of example and counterexample" predominates (Toribio, 2017: 228). Unifying the findings from these comparisons has proved challenging due to their differing methodologies and populations sampled (e.g., [START_REF] Fairchild | Determiner-noun code-switching in Spanish heritage speakers[END_REF][START_REF] Herring | I saw the madre': Evaluating predictions about codeswitched determiner-noun sequences using Spanish-English and Welsh-English data[END_REF]Pablos, Parafita Couto, Boutonnet, Jong, Perquin, Haan & Schiller, 2018;[START_REF] Couto | How do Welsh-English bilinguals deal with conflict? Adjective-noun order resolution[END_REF][START_REF] Couto | Testing alternative theoretical accounts of code-switching using event-related brain potentials: A pilot study on Welsh-English[END_REF][START_REF] Urbaneja | Tú tienes una little pumpkin?" Mixed noun phrases in Spanish-English bilingual children and adults[END_REF][START_REF] Evans | Switchmate! An electrophysiological attempt to adjudicate between competing accounts of adjective-noun code-switching[END_REF]. Furthermore, contrasts between constraint-free approaches and the MLF, in particular, have yielded findings either inconclusive or consistent with both accounts (e.g., [START_REF] Couto | How do Welsh-English bilinguals deal with conflict? Adjective-noun order resolution[END_REF][START_REF] Eppler | Evaluating the predictions of three syntactic frameworks for mixed determiner-noun constructions[END_REF][START_REF] Pablos | Adjective-noun order in Papiamento-Dutch code-switching[END_REF][START_REF] Couto | Code-switching within the noun phrase: Evidence from three corpora[END_REF]. We propose that there are two key challenges that need to be addressed in order to move away from this current situation; the integration of community norms into theoretical frameworks, and the need for more multi-method studies. Moreover, the field would greatly benefit from the same multiple methods being applied across communities in a systematic and coordinated fashion.

Challenge 1: Role of community norms

Despite the inclusion of community norms in some explanatory models of CS (e.g. [START_REF] Muysken | Bilingual Speech: A typology of code-mixing[END_REF]Backus, 2005), the role of local speech practices remains underrepresented in much CS research to date (cf. [START_REF] Chan | Code-switching between typologically distinct languages[END_REF]. If we understand that the acquisition of code-switching, similarly to the acquisition of one language, occurs through exposure to the production of other speakers within the community, it is plausible that the acquisition of CS patterns should reflect practices of the community, rather than varying based only on language-internal principles. If unaccounted for, community norms can confound results obtained from a single language pair and a single speaker community, hindering efforts to generalize these results into universal accounts of codeswitching structure.

However, most of the theoretical approaches focused on CS rely on single-community data for each language pair, ignoring factors related to local CS practices. This overall neglect displays what Haspelmath (2020) describes as a "cognitive bias" throughout the last few decades in linguistics, causing the cultural aspect of language to be sidestepped.

In order to overcome this bias, to account for the potential interacting role of community norms, and to develop better evaluations of the existing structural accounts of codeswitching, systematic cross-community comparisons within and between language pairs are necessary. By conducting such studies, CS researchers will be able to identify universal versus community-specific aspects of CS structure (see Sections 2-4).

Challenge 2: Comparing results across methodologies

Despite a wealth of observations of CS structures in different language pairs, their frequency distributions in naturalistic data have not yet made it possible to reliably differentiate between the predictions of different theoretical accounts. While CS research has expanded from well-established methods (e.g., acceptability judgements) to new ones (e.g., elicited production paradigms; electrophysiological measures), conflicting results from naturalistic and experimental studies raise concerns about the reliability of employing any single methodology in isolation, as well as regarding the interpretation of data from different sources. Indeed, researchers have highlighted the importance of systematizing corpus-building and access to naturalistic code-switching data [START_REF] Toribio | Structural approaches to code-switching[END_REF], developing rigorous experimental designs, and combining methodological approaches [START_REF] Gullberg | Research techniques for the study of code-switching[END_REF][START_REF] Munarriz-Ibarrola | Methodologies for intrasentential code-switching research[END_REF].

The objective of raising these two confounds, community norms and methodological comparisons, is not to discount the impact of single-community or single-methodology data, which remain relevant to the description of the specific communities to which they refer. Rather, only by providing converging data from different methodologies and comparing performances across communities can we investigate effects specific to the community and to dissociate those from potential universal tendencies in code-switching and structural effects of the languages involved.

In what follows we will focus on three code-switching phenomena: asymmetries in the language and gender of the determiner (Section 2), the relative order of adjective and nouns (i.e., conflict sites) (Section 3) and the creation of mixed language verbs (Section 4). We present data to illustrate these phenomena using a multimethod comparative approach, linking linguistic, psycholinguistic and social factors. This enables us to discuss the extent to which bilinguals (i) produce strings that can be seen as having the same syntactic structure, (ii), make the same linguistic judgements, and (iii) converge in their processing of these strings.

Asymmetries in the DP

Language of the determiner

Previous work on Spanish-English code-switching has revealed an asymmetry whereby mixed nominal constructions with a Spanish determiner, e.g. el book, are more commonly produced than those with an English determiner, e.g. the libro [START_REF] Liceras | Gender and gender agreement in bilingual native and non-native grammars: A view from child and adult functional-lexical mixings[END_REF][START_REF] Quintanilla | The semantic interpretation and syntactic distribution of determiner phrases in Spanish-English codeswitching[END_REF][START_REF] Kroff | Mixed NPs in Spanish-English bilingual speech: Using a corpus-based approach to inform models of sentence processing[END_REF]. [START_REF] Liceras | Gender and gender agreement in bilingual native and non-native grammars: A view from child and adult functional-lexical mixings[END_REF] explain this by suggesting that bilingual speakers favor the determiner with the largest number of uninterpretable features (here, Spanish), labeling this the grammatical features spell-out hypothesis (see also [START_REF] Quintanilla | The semantic interpretation and syntactic distribution of determiner phrases in Spanish/English codeswitching[END_REF][START_REF] Disciullo | On the asymmetric nature of the operations of grammar: Evidence from codeswitching[END_REF]. However, these studies do not control for the broader morpho-syntactic frame of the clause surrounding the DP. This interaction is particularly relevant, as the Bilingual NP Hypothesis within the Matrix Language Frame Model predicts that determiners in mixed nominal constructions should come from the matrix language of the clause [START_REF] Jake | Making a minimalist approach to code-switching work: Adding the matrix language[END_REF]. According to this account, Spanish determiners are predicted to surface in clauses with a Spanish matrix language, whereas English determiners are predicted to surface in clauses with an English matrix language.

Accounting for the matrix language of the clause, Herring, Deuchar, Parafita Couto and Moro Quintanilla (2010) investigated the use of determiners in mixed Spanish-English Determiner-Noun constructions in a sample of the Bangor Miami Corpus (http://bangortalk.org.uk). They observed, in accordance with the established asymmetry, that mixed DPs with Spanish determiners are more frequently observed than those with English determiners (see Table 2). More importantly the language of the determiner almost always matched the language of the verb and, therefore, the matrix language of the clause, supporting the Bilingual NP Hypothesis. Following up, [START_REF] Blokzijl | Determiner asymmetry in mixed nominal constructions: The role of grammatical factors in data from Miami and Nicaragua[END_REF] compared the entire Miami corpus with data from sociolinguistic interviews with Spanish-English creole speakers in Nicaragua, and found the opposite pattern of determiner use between the two corpora. In the Nicaraguan corpus, all of the mixed DPs featured an English determiner, yet none with a Spanish determiner were observed. But, similar to the pattern found in the Miami corpus, the language of the determiner always matched the matrix language of the utterance. A summary of the frequencies of these constructions in both corpora can be found in Figure 1. Note: Noun phrases (NPs) are divided between mixed and unmixed, between those with a match between the matrix language and the language of the determiner (match) or not (non-match), and between the language of the determiner matching with the matrix language (Spanish or English).

Moving beyond purely Spanish-English studies, Parafita Couto and Gullberg (2019) compared the language of the determiner in mixed DPs in corpora of Welsh-English, Spanish-English, and Papiamento-Dutch bilingual speech. In each of these pairs, one of the languages featured grammatical gender (Spanish, Welsh and Dutch) and the other did not (English and Papiamento). Their results for Welsh-English DPs show a preference for Welsh determiners, while Welsh was also the matrix language in all of the utterances. For Papiamento-Dutch, Papiamento was the preferred language for the determiner and the matrix language of all utterances. Finally, for Spanish-English, Spanish determiners were predominantly preferred, and Spanish was the matrix language in the majority (79%) of utterances. These results indicate an effect of the language of the morphosyntactic frame on the choice of determiner, in alignment with the Bilingual NP Hypothesis [START_REF] Jake | Making a minimalist approach to code-switching work: Adding the matrix language[END_REF]. The presence of grammatical gender coincided with the language of the determiner in Welsh-English and in Spanish-English, but not in Papiamento-Dutch, contrary to predictions following [START_REF] Liceras | Gender and gender agreement in bilingual native and non-native grammars: A view from child and adult functional-lexical mixings[END_REF] and Moro [START_REF] Quintanilla | The semantic interpretation and syntactic distribution of determiner phrases in Spanish-English codeswitching[END_REF]. Table 2 provides an overview of recent studies and datasets, all of which show a match between determiner and matrix language.

Dutch-Papiamento

MPI Corpus

• 25 adult speakers (15 female) Taken together, the corpora results highlight both a striking symmetry and asymmetry across language pairs. They all show a co-occurrence of finiteness (i.e. the matrix language) and the language of the determiner, contrary to the claims of lexicalist approaches [START_REF] Liceras | Gender and gender agreement in bilingual native and non-native grammars: A view from child and adult functional-lexical mixings[END_REF][START_REF] Quintanilla | The semantic interpretation and syntactic distribution of determiner phrases in Spanish-English codeswitching[END_REF]). Yet despite the consistency between the matrix language and the language of the determiner, different preferences for the matrix language emerged across language pairs and communities. But why is this? It has been suggested that differences could originate from social factors, such as the language of power or prestige in a community (e.g. [START_REF] Blokzijl | Determiner asymmetry in mixed nominal constructions: The role of grammatical factors in data from Miami and Nicaragua[END_REF][START_REF] Couto | Code-switching within the noun phrase: Evidence from three corpora[END_REF].

Complementing the production data reported above, acceptability judgements have also been collected. Since production frequency may not necessarily reflect ungrammaticality, acceptability judgments can supplement naturalistic data with negative evidence against dispreferred constructions. To this end, Parafita Couto and Stadthagen-González (2019) manipulated the language of the determiner and the matrix language of Spanish-English code-switched sentences, employing two types of acceptability judgement tasks: a traditional Likert-scale acceptability judgement and a two-alternative forced-choice acceptability judgement (2AFC) task. These tasks were compared in light of issues identified with the use of acceptability judgments in code-switching research, as traditional acceptability judgements might be sensitive to negative attitudes against codeswitching held by bilingual speakers. Both tasks yielded similar results, whereby constructions with Spanish and English determiners were accepted in similar rates, as long as the language of the determiner matched that of the matrix language of the clause.

The judgment results confirm those from the corpora, namely that the language of the determiner in mixed DPs generally matches the matrix language, but that the choice of matrix language may vary between communities and language pairs. This suggests that bilingual communities do not always follow the same pattern, and that social rather than grammatical factors may be at play in this asymmetry.

Gender of the determiner

If the determiner in a mixed DP comes from a gendered language (i.e. where gender is marked on the determiner), then it must be marked for gender. It is often the case that the noun comes from a genderless language, as in (2), an attested switch between gender-marked Spanish elements and an English noun (marked in bold in the examples). While masculine gender was used in (2), producing the same construction using feminine gender would not alter the semantic content of the utterance (3). This line of research therefore investigates whether bilingual speakers show a preference for one of the possible combinatorial forms.

( Speakers may adopt one of the gender values and assign it to all other-language nouns, a strategy referred to as the default. Naturalistic production data from Spanish-English bilinguals in the Miami corpus shows that, in mixed determiner-noun constructions with a Spanish determiner, the vast majority of the determiners carry masculine gender (97.4%) compared to just 2.5% with a feminine determiner [START_REF] Kroff | Mixed NPs in Spanish-English bilingual speech: Using a corpus-based approach to inform models of sentence processing[END_REF]. The same pattern was found in the use of gender by 62 Spanish-English bilinguals in northern Belize; almost every mixed construction (99.6%) contained a masculine determiner. Notably, even feminine nouns with female animate referents, such as el Virgen Mary 'the Virgin Mary' and los nuns 'the nuns', were accompanied by masculine determiners [START_REF] Balam | Mixed verbs in contact Spanish: Patterns of use among emergent and dynamic bi/multilinguals[END_REF].

In addition to the (masculine) default, two other main gender assignment strategies have been attested. First is assignment based on the gender of the translation equivalent of the other-language noun (also called the analogical criterion): for example, the English noun cookie may be assigned feminine gender (i.e. preceded by the feminine determiner la) because its equivalent in Spanish, galleta, is a feminine noun [START_REF] Delgado | The familiar and the strange: Gender assignment in Spanish/English mixed DPs[END_REF]. Second, we find assignment based on the (morpho-)phonological shape of the inserted noun. For example, the Basque noun liburua 'book' may be assigned feminine Spanish gender due the presence of the final -a, a cue that canonically indicates feminine gender on Spanish nouns (e.g., Parafita Couto et al., 2015).

The strategies employed by bilingual speakers in code-switching contexts vary, even within the same language pair, depending on the tasks employed, the modality of testing (written versus auditory), and the participant profiles. Table 4 illustrates this variation with results from a number of previous studies involving Spanish as the gendered language. We can observe that the analogical criterion is only favored by Spanish L1 bilinguals, that is, by speakers who acquired the language with grammatical gender first (cf. [START_REF] Liceras | Gender and gender agreement in bilingual native and non-native grammars: A view from child and adult functional-lexical mixings[END_REF]. This distribution of use of the analogical strategy seems to be consistent across the communities sampled to date, indicating an effect of order of acquisition. In contrast, the use of a default gender is widespread and its frequency appears to be related to the frequency of CS in a community; more habitual code-switchers switch more than non-habitual ones (Królikowska et al., 2019). Similar trends have also been noted for Spanish, Papiamento and Turkish heritage bilinguals in The Netherlands [START_REF] Boers | Gender in Unilingual and Mixed Speech of Spanish Heritage Speakers in The Netherlands[END_REF]. For a comprehensive overview of gender assignment preferences in bilingual communities and a discussion their possible conditioning factors, see Bellamy and Parafita Couto (accepted).

Acquisition of gender assignment strategies

Differences within the same language pair, as well as the observed asymmetries they produce, highlight the role of exposure to community norms during the acquisition of code-switching patterns. Asymmetries such as the use of a default gender assignment strategy are not obtained during the acquisition of the individual language systems (e.g., English and Spanish), but "must be learned amongst a community of codeswitchers" (Valdés Kroff, 2016: 297). This raises the key question as to when these asymmetries are acquired by bilingual children. To date, only a small number of studies have made a detailed comparison of the specific morphosyntactic patterns found in corpora of adult and child multilingual language usage (cf. Deuchar, forthcoming).

Recently, Balam, Lakshmanan and Parafita Couto (2021) investigated the production of grammatical gender by 40 Spanish-English bilingual children (aged 7-8 and 10-11 in both English immersion and two-way bilingual school programs) in Frog Story narratives in Miami Dade, Florida. For unilingual Spanish constructions, the authors found that all children used both feminine and masculine gender determiners, and produced gender assignment errors in less than 5% of the recorded examples. This strongly suggests that the children had successfully acquired the Spanish gender system. As for mixed DPs (n = 220), children used predominantly masculine determiners (in 97.8% of instances), a default pattern similar to that also reported for adult speakers in Miami (e.g., Valdés [START_REF] Kroff | Mixed NPs in Spanish-English bilingual speech: Using a corpus-based approach to inform models of sentence processing[END_REF]. Therefore, these bilingual children seem to have acquired both the gender system of the gendered language, Spanish, as well as the community patterns for the use of (masculine) gender in code-switching mode, as early as the age of seven (cf. [START_REF] Liceras | Gender and gender agreement in bilingual native and non-native grammars: A view from child and adult functional-lexical mixings[END_REF] who find both analogical and default strategies amongst 2L1 Spanish-English children in Spain).

We recommend that future research should use adult data to establish bilingual communicative norms across communities, and then, assuming it is representative of the community input to children, the children's bilingual communicative patterns should be studied in relation to the community norms. We expect that such an approach would provide very different adult and, perhaps also child, language distribution patterns which could be highly informative in cross-community comparisons.

Conflict sites: Adjective-noun order

In this section we will present conversational, judgment and EEG data to demonstrate how bilingual speakers deal with conflicting linear orders of nouns and adjectives in mixed NPs. Conflict sites in code-switching, as introduced by Poplack and Meechan (1998: 132), are "a form or class of forms which differs functionally, structurally, and/or quantitatively across comparison varieties". The target structure here is a complex NP comprising a determiner, an adjective and a noun. For instance, languages such as Dutch typically favor an Adjective-Noun word order (4), whereas a Noun-Adjective word order prevails in languages such as Papiamento ( 5).

(4) un refresco berde DET drink green 'a green drink' ( 5) een groen drank-je DET green drink-DIM 'a green drink' A switch between the noun and adjective (or vice versa in linear terms) would violate the Equivalence Constraint [START_REF] Poplack | The notion of the plural in Puerto Rican Spanish: Constraints on (s) deletion[END_REF][START_REF] Sankoff | A Formal Grammar for Code-switching[END_REF] and should therefore not occur. Yet naturalistic data shows that they clearly do; take the Papiamentu-Dutch un dushi verblijf 'a nice stay', for example, where the Papiamentu adjective precedes the Dutch noun, contrary to canonical unilingual constituent order (Parafita [START_REF] Couto | Code-switching within the noun phrase: Evidence from three corpora[END_REF].

Different theoretical frameworks make competing predictions regarding which adjectivenoun linear orders would be attested and accepted in mixed complex NPs. For example, within the Minimalist Program, [START_REF] Cantone | Adjectives and word order: A focus on Italian-German codeswitching[END_REF] arrive at the descriptive generalization that the language of the adjective determines whether it appears before or after the noun (cf. [START_REF] Cinque | The dual source of adjectives and phrasal movement in the Romance DP[END_REF]. In contrast, the morpheme-order principle within the MLF states that adjective-noun order will match the word order of the matrix language of the utterance, regardless of the language of the adjective [START_REF] Myers-Scotton | Contact linguistics: Bilingual encounters and grammatical outcomes[END_REF].

Let us begin with findings from naturalistic data. Mixed NPs containing a determiner, noun and adjective from Welsh-English, Spanish-English, and Papiamento-Dutch (where the first language of the pair has post-nominal adjectives and the second, prenominal) showed that most switches occurred between the determiner and the adjective-noun cluster, and that word order within those same language clusters generally followed the language of the adjective [START_REF] Couto | Code-switching within the noun phrase: Evidence from three corpora[END_REF]. However, in the nine instances with switches between noun and adjective, the matrix language predicted the observed word order. Counterexamples to the predictions of Catone and MacSwan (2009) were found in the Welsh-English and Papiamentu-Dutch corpus, where English (n=1) and Dutch (n=6) adjectives in postnominal position. Similar patterns were also observed in the naturalistic production data of Spanish-English bilinguals in Northern Belize [START_REF] Balam | Adjectives in Spanish/English codeswitching: Avoidance of grammatical gender in bi/multilingual speech[END_REF], as well as by Spanish-English bilingual children and adults in the USA (Ramírez Urbaneja, 2020). [START_REF] Couto | How do Welsh-English bilinguals deal with conflict? Adjective-noun order resolution[END_REF] addressed the same phenomenon in Welsh-English code-switching, using a multi-method approach that included the comparison of naturalistic production data, elicited productions, and acceptability judgements. The naturalistic production results show a preference for post-nominal adjectives (94.1%), regardless of the language of the adjective. These results do not fully support a matrix language or a generative based account of nominal word order. The authors point out that since Welsh is the only matrix language found in the corpus, it is not possible to contrast both models as the data generally adheres to the predictions of both models. Elicitation data from a Director-Matcher Task [START_REF] Gullberg | Research techniques for the study of code-switching[END_REF] contained 168 mixed NPs including an adjective. Just like in the naturalistic production data, in all instances Welsh was also the matrix language. These mixed NPs included mostly English noun insertions with post-nominal Welsh adjectives (n = 132), although combinations of a Welsh noun and an English adjective (n = 15) as well as unilingual English constructions with postnominal adjectives (n = 13) were also recorded. The data from the judgment task was not useful as participants rejected all stimuli, probably due to the stigmatized nature of codeswitching in this community.

Unlike production and judgment tasks, electrophysiological data has the potential to measure more automatic reactions, as this technique appeals less to participants' metalinguistic knowledge and attitudes. However, there is a scarcity of Event Related Potential (ERP) studies examining switching between different items within the sentence level (at a conflict site), where both semantic and syntactic information need to be integrated. An initial study on Welsh-English mixed NPs by [START_REF] Couto | Testing alternative theoretical accounts of code-switching using event-related brain potentials: A pilot study on Welsh-English[END_REF] compared sentences in which the word order supported the predictions of the MLF (Myers-Scotton, 2002), of [START_REF] Cantone | Adjectives and word order: A focus on Italian-German codeswitching[END_REF], violated both predictions, or supported both predictions. Sentences including a mixed nominal construction were visually presented to participants (n = 20) word-by-word, and scalp potentials were measured after the onset of the adjective. The authors found a larger amplitude in the positive-going waveform peaking approximately 300ms following the presentation of the adjective for the condition in which the MLF prediction was supported, compared to the condition in which Cantone and MacSwan's prediction was supported. However, no significant differences in amplitude were found in the comparison between the condition in which both predictions were supported versus the one in which they were both rejected. One potential explanation for this result is that participants were slightly more dominant in Welsh, and this might have lead them to activate Welsh syntax in processing the stimuli where the morphosyntactic frame is English but the noun adjective order is Welsh (Sanoudaki & Thierry, 2014). Another factor that may explain the null results in this comparison is that the adjective occurred in sentence-final position, which may lead to wrap-up effects [START_REF] Hagoort | Interplay between syntax and semantics during sentence comprehension: ERP effects of combining syntactic and semantic violations[END_REF].The authors acknowledge this limitation and suggest that in a future study the inclusion of a prepositional or adverbial phrase at the end of the sentence may help to settle these ambiguous results.

A similar study was conducted for Papiamento-Dutch mixed NPs [START_REF] Pablos | Adjective-noun order in Papiamento-Dutch code-switching[END_REF]. Event-related potentials were also measured following the rapid serial visual presentation to participants (n = 20) of sentences manipulated to fulfill the matrix language versus adjective-based predictions. No significant difference at any latency or at any particular location could be found in the analysis of the comparisons conducted. These results could suggest that CS is not restricted at modification sites in Papiamentu-Dutch bilinguals (cf. DiSciullo, 2014), or they might even suggest that CS is completely disallowed (cf. [START_REF] Poplack | The notion of the plural in Puerto Rican Spanish: Constraints on (s) deletion[END_REF] Equivalence Constraint) in this community. [START_REF] Couto | Testing alternative theoretical accounts of code-switching using event-related brain potentials: A pilot study on Welsh-English[END_REF] to avoid potential wrap-up effects, and also included additional sentence conditions to make it possible to compare across different matrix languages. The results reflect the switching pattern that has previously been reported in naturalistic production in this bilingual community (Parafita Couto et al., 2015), namely a preference for noun (rather than adjective) insertions. Moreover, the analyses also revealed that predictions of the MLF and the Minimalist Program manifest differently depending on the matrix language of the sentence: when the matrix language was Welsh, sentences that violated both theoretical predictions required greater processing effort. However, when the matrix language was English, ERP responses were not significantly modulated by either set of predictions. It was concluded that the processing of code-switched structures should reflect context-specific patterns that reveal themselves both in production and grammatical judgments (e.g. [START_REF] Beatty-Martínez | From the Field to the Lab: A Converging Methods Approach to the Study of Codeswitching[END_REF][START_REF] Balam | Bilingual verbs in three Spanish/English code-switching communities[END_REF].

The competing theoretical predictions have also been tested using judgment tasks. Stadthagen-González, Parafita Couto, Párraga and Damian (2019) tested 42 early Spanish-English bilingual employing both a 5 point Likert scale judgment task and a two alternative forced choice task. Their results revealed an additive effect, as both the language of the matrix language and the language of the adjective determine word order. [START_REF] Voss | Insights from Comparative Judgements of Adjective-Noun Order in Papiamento-Dutch Code-Switching[END_REF] replicated the same findings in a sample of Papiamento-Dutch bilinguals. These resuls suggest, as argued by Stadthagen-González et al. (2019) and [START_REF] Voss | Insights from Comparative Judgements of Adjective-Noun Order in Papiamento-Dutch Code-Switching[END_REF], that progress in our understanding of code-switching can be made by incorporating observations from different frameworks rather than considering them in isolation.

Once again, we can observe strikingly similar patterns across communities. In production, there is a clear avoidance of adjective-noun order switches and a preference for noun insertions. Recent neurophysiological data for Welsh-English [START_REF] Evans | Switchmate! An electrophysiological attempt to adjudicate between competing accounts of adjective-noun code-switching[END_REF]) also indicate a preference for noun insertions, and seem to reflect production patterns, which are guided by the matrix language of the utterance. Finally, judgment tasks show an overall sensitivity to both the language of the adjective and of the matrix language of the utterance. Noun insertions are preferred in this modality too, but where an adjective is inserted, speaker preference is for it to follow the order of the language from which is comes.

Creativity: Bilingual Verbs

Naturalistic productions from a range of language pairs have demonstrated that bilingual speakers can combine an inflected auxiliary verb in one language (e.g., "do" or "make") and an infinitive from another language (e.g., Hindi/English Creole, [START_REF] Muysken | Bilingual Speech: A typology of code-mixing[END_REF]Bengali/English, Chatterjee, 2012;Spanish/English Creole, Fuller Medina, 2005;[START_REF] Balam | A congruence approach to the study of bilingual compound verbs in Northern Belize contact Spanish[END_REF][START_REF] Balam | Code-switching and linguistic evolution: The case of "hacer + V" in orange walk, Northern Belize[END_REF]Spanish/English, Jenkins, 2003;Spanish/German, González Vilbazo, 2005;[START_REF] González-Vilbazo | Some properties of light verbs in codeswitching[END_REF]. While these constructions are prevalent cross-linguistically and have been proposed as a potential universal property of code-switching [START_REF] Edwards | Compound verbs in codeswitching: Bilinguals make do?[END_REF], the use of auxiliaries as light verbs may not be paralleled in the unilingual speech of the languages involved. These constructions, labelled as "bilingual light verb constructions" [START_REF] Balam | Mixed verbs in contact Spanish: Patterns of use among emergent and dynamic bi/multilinguals[END_REF], "bilingual compound verbs" [START_REF] Edwards | Compound verbs in codeswitching: Bilinguals make do?[END_REF], or "doconstructions" (Myers-Scotton 2002), among others, pose the question of how bilingual speakers may create code-switched constructions not readily explained by the grammars of each language.

In Spanish, for instance, the monolingual verb hacer 'do, make' can function both as a lexical verb of creation and as a causative verb. When incorporated into German-Spanish code-switching, hacer is also used as a light verb, losing much of its semantic content (4). This use is, however, restricted to code-switching contexts [START_REF] González-Vilbazo | Die Syntax des Code-Switching[END_REF][START_REF] González-Vilbazo | Some properties of light verbs in codeswitching[END_REF] The absence of a unilingual hacer light verb cannot be explained by a lexical property of the auxiliary if separate lexicons are assumed, since a Spanish verb cannot select for a German verb that is not part of the Spanish lexicon. Indeed, González-Vilbazo and López (2011) interpret hacer in mixed speech as a "last resort" realization of little v, whereas in Spanish such a last resort is never necessary. Because bilingual verbs cannot be understood solely on the characteristics of the corresponding monolingual verbs, it becomes important to identify what other factors may modulate how these verbs are used and how these constructions emerge.

In mixed verbs more generally, one language provides the auxiliary or light verb while the other provides the lexical verb, as observed earlier in (4). Two principal constructions are attested for mixed Spanish-English verbs: hacer 'do, make' + VINF (5) and estar 'be' + VINF (6).

( Pfaff, 1979: 296) In the naturalistic production of Spanish-English bilinguals, the hacer + VINF construction is attested in Belize [START_REF] Balam | Code-switching and linguistic evolution: The case of "hacer + V" in orange walk, Northern Belize[END_REF][START_REF] Balam | Mixed verbs in contact Spanish: Patterns of use among emergent and dynamic bi/multilinguals[END_REF][START_REF] Balam | A congruence approach to the study of bilingual compound verbs in Northern Belize contact Spanish[END_REF], as well as in the southwestern USA [START_REF] Reyes | Language mixing in Chicano Spanish[END_REF][START_REF] Jenkins | Bilingual verb constructions in southwestern Spanish[END_REF][START_REF] Vergara Wilson | One construction, two source languages: Hacer with an English infinitive in bilingual discourse[END_REF][START_REF] Vergara Wilson | The emergent grammar of bilinguals: The Spanish verb hacer 'do' with a bare English infinitive[END_REF]. In contrast, estar + VINF combinations are attested infrequently in both the Miami corpus (n = 7) and 88 entries of La Calentita: Gibraltar's National Dish, an editorial column from the Gibraltarian newspaper Panorama (n = 8; Guzzardo Tamargo, 2012).

However, while there may be some cross-community differences in oral production, these differences may not necessarily be present at the level of judgment. 2011) seems to be tied to its exposure and use in naturalistic speech. There are also more sociolinguistic implications: As the northern Belize and Puerto Rican groups show opposite preferences, it may be that intuitions about bilingual verbs may be communityspecific, being influenced by participants' previous exposure to these different forms.

The combination of production and acceptability judgement data on bilingual verbs across Spanish-English bilingual communities indicates that this phenomenon, previously proposed as a code-switching universal [START_REF] Edwards | Compound verbs in codeswitching: Bilinguals make do?[END_REF], is also subject to the effect of the differential exposure bilingual speakers have to each structure. Results from specific communities, such as Belize, further indicate that the frequency and productivity of bilingual verbs can be subject to other language-external factors [START_REF] Balam | Mixed verbs in contact Spanish: Patterns of use among emergent and dynamic bi/multilinguals[END_REF].

Conclusion

The case studies provided in the previous sections highlight that, for each codeswitching phenomenon, we can observe both uniformity and variability. For determinernoun switches, the co-occurrence of finiteness and determiner in the same language (i.e. the matrix language) occurs across communities, whereas the choice of matrix language varies. The translation equivalent strategy of gender assignment in mixed NPs is preferred among bilinguals whose L1 possesses gender, whereas the strategy applied can vary between language communities and pairs according to the bilingual profile, CS frequency and the tasks completed. In terms of linear noun-adjective order, we see a preference for noun insertions across the board, as well as for the adjective and noun to be in the same language -switches between these two constituents are not common. However, variation in this mixed structure is yet to be described in detail. As for bilingual verbs, studies across several communities of the same language pair have revealed the estar + VPROG construction to be the most acceptable, but the presence and acceptability of hacer + VINF to be acceptable to varying degrees, depending on the patterns previously reported in production in these communities.

From this review of asymmetry and conflict sites in the nominal domain, as well as creativity in the verbal domain, we aimed to address the extent to which these codeswitching phenomena vary or remain stable across language pairs and communities. These findings strongly suggest that asymmetries are due to extralinguistic factors, such as community norms, rather than structural properties of the participating languages. By presenting results stemming from different data collection mechanisms, we have also demonstrated how a multi-method approach provides a more robust overview of patterns underpinning code-switching behavior. In order to probe these interactions between linguistic and extra-linguistic factors further, we have shown that more research is needed, in both the nominal and verbal domains, across language pairs, between the same language pair but across communities, as well as in the same language pair but between individuals, namely adults vs. children. By building a stronger -and more coordinatedevidence base, we can begin to better understand the nature of bilingual interactions, which will enable us to ultimately build better models of language competence.

Figure 1 .

 1 Figure 1. Nominal construction frequencies in the Bangor Miami Corpus and the Nicaragua Corpus

Following

  the methodological recommendations by Parafita Couto et al. (2017), Vaughan Evans et al (2020) made a further attempt to use ERP data to reconcile theoretical predictions in relation to linear adjective-noun order. They adapted the stimuli of Parafita

Table 2 .

 2 Naturalistic production datasets showing a match between determiner and matrix language in mixed determiner-noun constructions.Parafita Couto, M. Carmen, Miriam Greidanus Romeli & Kate Bellamy. 2021. Code-switching at the interface between language, culture, and cognition, Lapurdum: Basque Studies Review.

	Language Pair	Corpus	Data characteristics	Studies
	Spanish-	Miami Corpus	• 85 adult speakers (52 female)	Herring et al. (2010):
	English		• Dyads	subset of 5:27h (19
			• Collected in Miami, FL, US	speakers) selected
			• Mixed NPs n=276	Blokzijl, Deuchar, &
				Parafita Couto (2017):
				full corpus
				Parafita Couto &
				Gullberg (2017):
				subset 5:27h/20 (19
				speakers) selected
		Nicaragua	• 42 adult speakers	Blokzijl, Deuchar, &
		Corpus	• 12 hours	Parafita Couto (2017):
			• Dyads or groups	full corpus
			• Collected in 2006 in the South
			Atlantic Coast area of
			Nicaragua
			• Mixed NPs n=142
		Las Pláticas	• 14 adult speakers	Ramírez-Urbaneja
		Corpus	• 10 hours	(2020): full corpus
			• Collected in 2018 in New
			Mexico, US
			• Mixed NPs n=259
		Three corpora	• 15 child speakers	Ramírez-Urbaneja
		from the	• Ages (1;11 to 6;4)	(2020): full corpora
		CHILDES database	• Collected in Los Angeles, CA, US, Michigan, US, and Spain
			• Mixed NPs n=202
	Welsh-English	Siarad Corpus	• 151 adult speakers (81 female)	Parafita Couto &
			• Dyads	Gullberg (2017):
			• Collected at the Centre for Research on Bilingualism,	subset of 18:40h /40 (42 speakers) selected
			Bangor, UK
			• Mixed NPs n=171

Table 4 .

 4 Summary of elicited production and acceptability judgement data on gender assignment strategies in mixed Determiner-Noun constructions.Parafita Couto, M. Carmen, Miriam Greidanus Romeli & Kate Bellamy. 2021. Code-switching at the interface between language, culture, and cognition, Lapurdum: Basque Studies Review.

	Studies	Data	Task(s)	Participants	Main results
		type
	Parafita Couto et al.	AJ*	Oral stimuli	30 early bilinguals	Feminine preferred (-
	(2015)		4 lexical items	(26 L1S-eL2B	a)
			(phonological	bilinguals, 4
				simultaneous)

*AJ = Acceptability judgment task, EP = Elicited production.

  . Note that the German verb is underlined.

	(4)	Vamos	a	hacer schreiben	la	Mathearbeit
		go.1PL	PREP do.INF write.INF	DET.FEM	maths.homework
		'We will write the maths homework.'
		(Adapted from González Vilbazo, 2005: 202)

  All groups accepted the estar bilingual construction, which has structural equivalents in both languages. Results for hacer, however, show different preferences in different communities. While bilinguals from northern Belize consider hacer + Vinf constructions the most acceptable, speakers from New Mexico preferred estar + Vprog, followed by hacer + Vinf constructions. Finally, Puerto Rican bilinguals strongly rejected all conditions, except estar + Vprog constructions. From a formal perspective, the acceptability of hacer (as an overt manifestation of little v (González Vilbazo & López

		To assess this possible
	discrepancy, Balam, Parafita Couto and Stadthagen-González (2020) ran a two alternative
	forced choice task with a total of 106 Spanish-English bilinguals in northern Belize (n =
	44), New Mexico (n = 32) and Puerto Rico (n = 30). The task comprised 72 items (36 test
	items and 36 fillers), controlled for tense, sentence length, lexical verb type, as previous
	work suggests that light verb constructions in contact Spanish primarily occur with
	transitive verbs (see Balam, 2015, 2016; Vergara Wilson & Dumont 2015). The four test
	conditions, including examples of each, were as follows:
	(A)	Hacer+ VProg: [hace auditing] el report.
	(B)	Estar+VInf: [está audit] el report.
	(C)	Hacer+VInf: [está haciendo audit] el report.
	(D)	Estar+VProg: [está auditing] el report.

ParafitaCouto, M. Carmen, Miriam Greidanus Romeli & Kate Bellamy. 2021. Code-switching at the interface between language, culture, and cognition, Lapurdum: Basque Studies Review.