Grammatical Innovation in Western Basque Varieties: The Emergent System of Conditional Gender Agreement

Abstract

Aims and objectives:

This study investigates a recent grammatical innovation in Western Basque: the emergence of a conditional grammatical gender agreement (GGA) system. While Basque is traditionally classified as morphologically genderless, this research examines how intense, long-term contact with Spanish has led to adjectival gender distinctions, shifting the language toward a new typological category.

Methodology:

The research utilizes a triangulated mixed-methods approach, combining a sentence completion task and a matched-guise test. Data were collected from 20 young adult traditional speakers (euskaldun zaharrak) in Mundaka (Bizkaia) and compared with data from the proximate community of Ondarroa to assess the impact of contact intensity on structural change.

Data and analysis:

Results demonstrate categorical use of feminine morphology (-ie) with female referents in Mundaka. Crucially, agreement extends beyond Spanish loanwords to native Basque-origin stems (e.g., gizajo/a, potolo/a), representing structural borrowing of inflectional morphology. Attitudinal data reveal that feminine morphology is perceived as significantly more natural and respectful than the masculine form for female referents, regardless of etymological origin.

Conclusions:

The findings confirm a ‘conditional’ GGA system that is lexically restricted but structurally entrenched. The contrast between rigid consensus in Mundaka and higher variability in Ondarroa suggests that borrowed features are mediated by local sociolinguistic pressure. This innovation represents ‘identity policing’, where speakers utilize borrowed categories to protect linguistic boundaries.

Originality:

This research provides the first systematic empirical evidence of Spanish-style gender agreement transferred onto native Basque inflectional morphology, refuting the view of Basque’s categorical resistance to gender categories.

Significance:

The study contributes to theories of structural permeability by demonstrating how core functional domains are reshaped under sustained pressure, offering a model for how genderless languages develop gender categories through social negotiation.

Keywords

grammatical gender agreement language contact production attitudes

Introduction

Basque (Euskera) is classically described as a language without grammatical gender agreement [GGA] (Euskaltzaindia, 1991, 2002). As a minoritized language, Basque is in close contact with the grammatical gender languages Spanish (in the Basque Autonomous Community and Navarre) and French (in the Northern Basque Country) (Gygax et al., 2019).

GGA systems are subject to change, including reduction or loss due to internal diachronic shifts (Corbett, 1991; Di Garbo, 2020; Igartua, 2019), such as the reduction from three to two genders in Romance languages. Crucially, both the loss and the emergence of gender can occur in intense language contact situations (Aikhenvald, 2016; Di Garbo, 2020). Research has extensively explored the influence of Basque’s genderlessness on contact varieties of Spanish, examining its effects on agreement in Old Spanish texts (Gómez Seibane, 2008) and in the Basque Spanish variety (e.g., Basterretxea Santiso, 2022, 2024, 2025; Parafita Couto et al., 2015).

The opposite process—the emergence of a (marginal) gender category in a genderless language due to contact—requires further research (Igartua, 2019). Cases of gender agreement patterns have been reported in some Western Basque varieties. For instance, Lekeitio Basque informal speech shows verbs derived from Spanish adjectives that index natural gender (Di Garbo, 2020; Hualde et al., 1994). Moreover, new empirical research on Ondarroa Basque considering production and attitudes shows that Spanish-style GGA is possible with Spanish-originated and even Basque adjectives, and that it is perceived not only as natural but also as respectful and integrated into Basque (Basterretxea Santiso et al., 2026).

This study seeks to advance the sociolinguistic description of Bizkaian coastal Basque by offering the first systematic analysis of GGA in the Mundaka variety. Specifically, it investigates whether adjectival gender distinctions surface with female referents, how such distinctions are morphologically encoded and perceived, and how these patterns compare to those documented for Ondarroa Basque (Basterretxea Santiso et al., 2026).

Background Literature

Gender Agreement in Basque

Gygax et al. (2019) classify Basque as fundamentally a language without GGA,¹ noting that while most personal nouns and pronouns refer to male or female entities, they lack distinct linguistic forms to encode that gender. Consequently, gender distinction in the lexicon is typically achieved through heteronyms (different words for male and female referents), such as ama ‘mother’ and aita ‘father’, or gizon ‘man’ and emakume ‘woman’ (Euskaltzaindia, 1991, 2002, 2021; Trask, 2003; Gómez Seibane, 2008; Zubiri & Zubiri, 2012).

Nevertheless, a few gendered forms appear in nouns, adjectives, or verbal forms. For instance, the use of the -sa suffix acts as a gender distinguisher in nouns: artzain (‘shepherd’) and artzaintsa (‘shepherdess’) (Gómez Seibane, 2008), or jainko (‘god’) and jainkosa (‘goddess’) (Trask, 2003; Zubiri & Zubiri, 2012). This phenomenon is also seen with loanwords such as aktore (‘actor’) and aktoresa (‘actress’) (Zabala & San Martin, 2012), and printze (‘prince’) and printzesa (‘princess’) (Zubiri & Zubiri, 2012). More recently, the use of alkatesa (‘mayor [fem.]’) has increased over the older form alkate andrea (‘female mayor’) (Euskaltzaindia, 2021).

In some Western Basque varieties, adjectives ending in -a can refer to female entities, whereas -o refers to males (Di Garbo & Miestamo, 2019; Hualde et al., 1994; Gómez Seibane, 2008; Padilla-Moyano, 2018; Parafita Couto et al., 2015; Trask, 2003). This Spanish-style gender marking is possible with adjectives derived from Spanish (katoliko/a ‘catholic’, majo/a ‘nice’, tonto/a ‘stupid’, or txulo/a ‘arrogant’) (Euskaltzaindia, 1991, 2002, 2021; Laka, 1996; Parafita Couto et al., 2015; Trask, 2003), and also with a limited number of adjectives not borrowed from any language (i.e., gixajo/a ‘poor’) (Gómez Seibane, 2008; Parafita Couto et al., 2015; Trask, 2003). This usage is limited to Western Basque varieties and categorized as modern and infrequent (Laka, 1996; Gómez Seibane, 2008; Parafita Couto et al., 2015; Trask, 2003). In fact, Trask (2003, p. 137) claims that ‘eastern varieties invariably borrow only the masculine form of a Romance adjective and apply it indiscriminately to both sexes in Basque’. However, in certain informal Western varieties, particularly in Lekeitio, this gender marking extends beyond simple attributive adjectives and infiltrates the verbal system. In these cases, verbs derived from Spanish adjectives—often expressing physical or emotional states—retain gender morphology in their participle forms when used with the auxiliary izan (Di Garbo, 2020; Hualde et al., 1994). For instance, while the standard and gender-neutral form would be mareatu (‘to get dizzy’), Lekeitio speakers may use mareadu for a male subject and mareadia for a female subject. This represents a significant grammatical shift, as the gender feature is no longer confined to a borrowed lexeme but begins to function as a marker of natural gender within the predicate, indexing the subject’s gender through a previously genderless verbal slot. Crucially, this emergent system remains restricted to human/biological gender. Unlike Spanish, which assigns grammatical gender to all inanimate nouns, the GGA system in varieties like Mundaka does not extend to inanimate objects (e.g., ‘the table’ remains gender-neutral). This restriction confirms its status as an ‘emergent’ and lexically constrained system rather than a fully transitioned gender architecture.

Recently, the first empirical study to explore the (in)existence of GGA in the Basque was conducted, utilizing data from Ondarroa Basque speakers (Basterretxea Santiso et al., 2026). The results of the study demonstrate that a GGA system is present in Ondarroa Basque speakers, and crucially, it is considered natural and fully integrated into their speech. Young adult speakers exhibited production of the agreement and acceptance of the system, which can be divided into at least three categories: (1) adjectives derived from Spanish with GGA as in feo/a ‘ugly’; (2) Basque adjectives ending in -o with possible Romance-style GGA like gizajo/a ‘poor’; and (3) Basque adjectives that do not end in -o without the possibility of producing GGA, except for a few innovations.

Case Studies: Mundaka and Ondarroa

Mundaka Basque and Ondarroa Basque, both belonging to the Western/Bizkaian dialect group as shown in Figure 1, reside in a typological zone that differs markedly from Standard Basque (Euskara Batua) in several morphological and lexical respects. This distinction makes them a valuable point of comparison for dialectology.

Their structural proximity to other Bizkaian varieties and the vitality of Basque within their communities make these two varieties important case studies for examining dialectal persistence and the complex interaction between Standard Basque and Spanish in contemporary Basque-speaking contexts. In both towns, Basque constitutes not merely a medium of communication but a central symbol of identity and belonging, sustained through local pride, community transmission, and its visibility in the linguistic landscape.

Figure 1.

The modern dialects of Basque (Zuazo, 2008).

Mundaka

Mundaka, a small coastal municipality in the province of Bizkaia, has a relatively high concentration of Basque speakers: with a population of 1,878 inhabitants, 68.37% reported using Basque daily (EUSTAT, 2021). The variety of Basque spoken in Mundaka belongs to the Western dialect group (Zuazo, 2008, 2019), and like the variety of Ondarroa, it shares several phonological and morphological traits with other Bizkaian coastal varieties such as Bermeo and Elantxobe. Within this dialect zone, the Basque spoken in Mundaka is part of the Busturialdea region, which historically has served as a major hub for linguistic innovation within numerous Bizkaian subdialects (Zuazo, 2019). By the 16th century, when Bilbao emerged as the provincial center, the Bizkaian dialect had already developed around the innovations originating from the central axis connecting Durango, Zornotza, Gernika, and Bermeo. However, Mundaka developed into an international residential and leisure destination. This profile—highlighted by its famous surfing break and large seasonal influx of Spanish-speaking tourists and second-home owners (veraneantes)—subjects the community to high external contact pressure and results in a state of linguistic porosity, where the use of Basque is consequently attenuated in public and commercial settings.

Ondarroa

Ondarroa, a coastal municipality in Bizkaia, has an exceptionally high rate of Basque speakers: with a population of 8,451 inhabitants, 76.60% reported using Basque daily (EUSTAT, 2021). While Basque is a minority language generally (Marten et al., 2012), it is the dominant language within Ondarroa’s linguistic landscape. The variety is a distinctive subvariety of the Western dialect (Amorrortu, 2003; Zuazo, 2019), owing its stability to relative geographic isolation and limited interregional contact (Zuazo, 2019). Crucially, Ondarroa is primarily a working fishing port, not a tourism center. This functional identity supports a more stable, local population with lower external contact pressure and a more intensely Basque-speaking landscape (Basterretxea Santiso & Ornelles, 2025) compared to Mundaka.

Different Suffixes

Although the Mundaka and Ondarroa varieties are both classified within the Western dialect of Basque, they exhibit distinct linguistic features regarding emergent gender morphology. Previous studies have noted that the suffixes -o (masculine) and -a (feminine) typically function as Romance-like gender markers in certain Western Basque varieties (e.g., Gómez Seibane, 2008; Trask, 2003). However, the specific morphological realization of these endings differs in Mundaka and Ondarroa, a variation attributed to a broader Bizkaian phonetic pattern involving changes to the final vowel of a stem when the determiner -a is attached (Amorrortu, 2003). The Romance-style gender agreement markers typically cited for Western Basque (-o and -a) correspond to -ue and -ie in Mundaka Basque and as -u and -i in Ondarroa Basque. This dialectal difference stems from how the final vowel of a stem also changes when combined with the determiner -a. Table 1 illustrates the local variation for stems ending in /a/ and /o/:

Table 1.

Example of Vowel Alternation.

Stem + Determiner	Western Bizkaian	Mundaka Basque	Ondarroa Basque
alaba + -a (‘the daughter’)	alabea	alabie	alabi
gogo + -a (‘the will’)	gogoa	gogue	gogu

The shift from Spanish -o/-a to Mundaka -ue/-ie reflects a systematic Bizkaian phonological rule where stem-final vowels diphthongize when merging with the Basque determiner -a. This adaptation indicates that the borrowed gender features have been fully integrated into the local phonological template rather than remaining as unassimilated Spanish clusters. By subjecting the Spanish-origin vowels to these native morphophonological rules, the Mundaka variety effectively ‘Basquizes’ the borrowed gender morphology.

Research Questions

To date, aside from Basterretxea Santiso et al. (2026) study on Ondarroa Basque, no empirical research has systematically investigated the presence of GGA in Basque. To contribute to this discussion, the present study examines and compares the Mundaka and Ondarroa Basque varieties. Employing a triangulated methodological approach that combines both production data and attitudinal evidence, the study seeks to address the following research questions:

RQ1: Does the Mundaka variety distinguish adjectives based on the gender of the referent? If so, how is this distinction morphologically realized, and does it differ from Ondarroa Basque?

RQ2: What implicit attitudes do Mundaka Basque speakers display toward the use of the feminine morpheme with female antecedents, in comparison with the use of the masculine morpheme with female antecedents? Do these attitudes vary from Ondarroa Basque speakers?

Methodology

Participants

Twenty speakers of the Mundaka Basque were recruited in 2025. The background questionnaire created by Gondra (2025) for the Basque context was employed, as in Basterretxea Santiso et al. (2026), to learn about their gender, year of birth, level of education, language background, and language of schooling. Information about participants’ gender and highest level of education is introduced in Table 2.

Table 2.

Participants’ Background Information.

Gender		Level of education
Female	12	High school	5
Male	8	Professional	4
Non-binary	0	Undergraduate	11
		Graduate	0
Total	20	Total	20

The oldest participant was born in 1997, while the youngest participant was born in 2004. Participants’ age median is 25.5 years old, considering them as young adults, the same as in Basterretxea Santiso et al. (2026). All participants were born and still live in Mundaka; they consider themselves speakers of Mundaka Basque as well as Bizkaian Basque, and their language of schooling was Basque (Model D).² All of them reported having learned Basque both at home and at school. This does not imply, however, that the sole language used at home was Basque: 14 participants reported using at least some Spanish with one of their parents at home.

Production

Participants were first prompted to complete an adaptation of the sentence completion task (SCT) used in Basterretxea Santiso et al. (2026) to gather hypothetical production data by controlling the context. An SCT ‘involves providing the beginning of a sentence and asking participants to complete the sentence in their own words’ (Drager, 2018: 100–101). The original version of the SCT used in Basterretxea Santiso et al. (2026) was written in Ondarroa Basque. To adapt to the new population, the new SCT was written in Mundaka Basque and reviewed by several Mundaka Basque speakers. Although in variationist sociolinguistics the ideal is to collect naturally occurring data, the use of surveys to explore variation in production is not new (Drager, 2018), and this method was chosen for comparability purposes with Basterretxea Santiso et al. (2026).

The structure of every sentence in the SCT was the same as in Basterretxea Santiso et al. (2026). Since the purpose was to obtain GGA production instances, participants had to complete the sentences by including the gender morpheme and verb to finish the sentence. All sentences followed the same pattern: hau ‘this’ neskie ‘girl’/mutile ‘boy’ + adjective (without the gender morpheme). Before starting the actual SCT, participants completed an example with one of the research team members to ensure that the task would be completed properly. The SCT included a total of 16 sentences that were descriptions of a person (Appendix 1). Each sentence was accompanied by a picture that described the sentence. To combine the possible use of masculine and feminine morphemes with female antecedents, a number of combinations were created. In addition, since it has been previously established that Spanish-style GGA is typically produced with Spanish-originated adjectives (Euskaltzaindia, 1991, 2002; Laka, 1996), both Spanish-originated and Basque-originated adjectives were chosen. Finally, sentences with male referents were introduced in the SCT to use as distractors. All these combinations are illustrated in Table 3. Sentences were presented in random order.

Table 3.

Classification of Sentences for the SCT.

16 sentences
8 sentences: male antecedent		8 sentences: female antecedent
Spanish-originated adjectives	4	Spanish-originated adjectives	4
Basque-originated adjectives	4	Basque-originated adjectives	4

The same adjectives as in Basterretxea Santiso et al. (2026) were employed in the SCT, modified into the Mundaka Basque, as presented in Table 4. There is an exception: one of the Basque-originated adjectives in Basterretxea Santiso et al. (2026) was lantzoi. This is the name of a fish (‘saury’), but it is also used in Ondarroa Basque as ‘stupid’ or ‘feckless’ (according to the Ondarruko Hiztegixe online dictionary of Ondarroan [Arrizabalaga Basterretxea, 2025]). Since this word is not, therefore, part of Mundaka Basque, potxolo (‘cute’) was chosen in its place, also because it follows the same pattern as the other adjectives (ends in -o in Standard Basque).

Table 4.

Adjectives Chosen for the SCT.

Spanish-originated adjectives		Basque-originated adjectives
Adjective	Translation	Adjective	Translation
guapo	‘handsome’	gizajo	‘poor’
listo	‘smart’	potxolo	‘cute’
majo	‘nice’	potolo	‘fat’
katoliko	‘catholic’	txotxolo	‘dumb’

Attitudes

To elicit implicit attitudinal data, the written matched-guise test [MGT] (Lambert et al., 1960) created by Basterretxea Santiso et al. (2026) was replicated and adapted to the Mundaka Basque for this research. This test was completed by the same participants who had first completed the SCT.

The MGT is composed of 31 guises (presented in Table 5), divided into two groups, based on the gender of the antecedent. The objective of the MGT was to compare implicit attitudes between the use of masculine and feminine morphemes with female antecedents. Therefore, when using a female referent, adjectives were presented twice, with a different gender morpheme in each case. Consequently, the 15 guises with a male antecedent were introduced to use as distractors. For triangulation purposes, the adjectives employed in this part of the research are the same as the ones chosen for the SCT. Guises were presented in random order.

Table 5.

Classification of Sentences for the MGT.

31 guises
15 guises: male antecedent		16 guises: female antecedent
Spanish-originated adjs	8	Spanish-originated adjs	4 masculine morpheme	4 feminine morpheme
Basque-originated adjs	7	Basque-originated adjs	4 masculine morpheme	4 feminine morpheme

With the aim of focusing participants’ attention on the gender agreement morpheme employed, all guises followed the same syntactic structure, which is the same that was created for the SCT: hau ‘this’ neskie ‘girl’/mutile ‘boy’ + adjective + da ‘is’. Before beginning the MGT, a practice sentence was provided for participants. Different from the SCT, no pictures were included in this test.

To gather implicit attitudes toward the guises, a 6-point semantic differential scale (1 = less; 6 = more) was adapted from Basterretxea Santiso et al. (2026) with opposite adjectives (Osgood, 1964). From the original test, the following opposite adjectives/descriptions were included: Euskaldun³ barrixe ‘Someone who has not acquired Basque from their parents in their early childhood’ versus Euskaldun zaharra ‘Basque native speaker’,⁴ Ez da oso esaldi naturala ‘Not a very natural sentence’ versus Oso esaldi naturala da ‘A very natural sentence’, Euskerie debekatute egon zaneko pertsonie ‘A person from when Basque was a forbidden language’ versus Euskeraz berba ein ahal dan epokako pertsonie ‘A person from when it is permitted to speak Basque’, Erderien eraginik ez ‘No effect of Spanish’ versus Erderien eragine bai ‘Effect of Spanish’, and Ikasketa gitxi dakozen pertsonie ‘Someone with a low level of education’ versus Ikasketa asko dakozen pertsonie ‘Someone with a high level of education’.⁵

After reading and evaluating each sentence, participants were asked whether they would say that same sentence in a hypothetical context (yes vs. no), to explore whether they think they would use masculine morphology with a female antecedent compared to feminine morphology with a female antecedent, without explicitly asking it. Results for this variable are included in Table 6: almost all participants rejected the sentences that employed masculine morphology with a female referent. On the contrary, all of them would say the sentences that used feminine morphology with a female referent. The original intention was to employ the results from Table 6 as an independent variable to predict attitudes in the MGT (similar to Basterretxea Santiso et al., 2026). Nevertheless, since there is no variation with regard to sentences using feminine morphology with a female referent, this independent variable will not be included in the analysis.

Table 6.

Sentences Participants Would Not Say (Always With a Female Referent).

Masculine agreement		Feminine agreement
Gizajue	18 participants	gizajie	0 participants
potxolue	18 participants	potxolie	0 participants
potolue	20 participants	potolie	0 participants
txotxolue	20 participants	txotxolie	0 participants
guapue	20 participants	guapie	0 participants
katolikue	20 participants	katolikie	0 participants
listue	19 participants	listie	0 participants
majue	19 participants	majie	0 participants

Researcher Positionality

The research team comprises native and near-native speakers of Basque with deep-seated familial and social ties to the Bizkaian coastal region. This insider status proved instrumental to the study’s methodological integrity; it not only facilitated trust during participant recruitment in the close-knit communities of Mundaka and Ondarroa but also ensured that the experimental stimuli and interview protocols utilized authentic local vernacular forms rather than standardized (Batua) equivalents. This shared linguistic background allowed for a nuanced elicitation of the specific Mundaka and Ondarroa morphological variants, minimizing the potential for ‘observer’s paradox’ and ensuring that the data reflect naturalistic, socially situated speech patterns.

Results

Production

Results from the SCT were explored descriptively, indicating that all participants always used the feminine morpheme with female referents. There was no distinction in production based on the adjectives’ linguistic origin (Basque vs. Spanish). Therefore, all participants used the following forms of the adjectives with female referents: gizajie ‘poor’, potxolie ‘cute’, potolie ‘fat’, txotxolie ‘dumb’, guapie ‘pretty’, listie ‘smart’, majie ‘nice’, and katolikie ‘catholic’.

Attitudes

Considering that it was likely for the adjectives used in the semantic differential scale to be connected, a factor analysis was conducted (following the indications by Bandalos & Boehm-Kaufman, 2008). Results of the factor analysis indicated the existence of one factor group along with two independent factors. The factor group was named ‘Basque speaker’, and it loads for the adjectives in reference to Basque native speakers, natural-sounding sentences, and level of education. The two independent factor groups are ‘Linguistic factor’ for the effect of Spanish, and ‘Social profile’ for the age adjective.⁶

Descriptive statistics are introduced in Figure 2 for each factor group extracted from the factor analysis, distinguishing the attitudes toward masculine morphology and feminine morphology employed with female referents. The dependent variable of the descriptive statistics is the mean obtained for each group in the 6-point semantic differential scale (1 = less; 6 = more).

Figure 2.

Mean scores for attitudes toward GGA with a female referent.

Based on descriptive statistics illustrated in Figure 2, and starting with the ‘Basque speaker’ factor group, the use of the feminine morphology with female antecedents is perceived as sounding more like a Basque speaker, natural, and a person with a higher level of education (M = 5.25, SD = 1.11, N = 20), than the use of masculine morphology with female antecedents (M = 2.3, SD = 1.25, N = 20). According to the paired sample t-test, this difference is statistically significant: t(19) = -12.4129, p = 1.460064e-10. Second, focusing on the ‘Linguistic factor’ as a proxy for receiving more effect of Spanish, the paired sample t-test showed that there is no significant difference (t(19) = -0.4811, p = .6359) between the perception of the use of the masculine morphology with female antecedents (M = 3.08, SD = 1.84, N = 20), and the use of feminine morphology with female antecedents (M = 2.89, SD = 2.08, N = 20). Third, ‘Social profile’ factor in terms of speakers’ age,⁷ the use of feminine morphology (M = 3.61, SD = 0.72, N = 20) and masculine morphology (M = 3.78, SD = 0.74, N = 20) receive very similar values, the absence of a boxplot in Figure 2 for masculine morphology indicating less variation among participants’ responses. According to the paired sample t-test, the difference between the two ratings is not statistically significant: t(19) = 1.1639, p = .2588.

Considering that scholars have previously mentioned that Spanish-style gender marking in Spanish is produced with Spanish-originated adjectives (Laka, 1996; Parafita Couto et al., 2015; Trask, 2003), mixed-effects logistic regressions with random effects for participants and adjectives, as well as ANOVAs, were calculated for each factor group in R (R Core Team, 2022) to explore possible significant interactions between the dependent and the independent variable (adjectives’ linguistic origin: Basque vs. Spanish), establishing alpha level in .05.

For the ‘Basque speaker’ factor group, results from the mixed-effect regressions introduced in Table 7 imply that there is only a significant difference based on the gender used with female referents (there is no significant interaction between the morphemes used with adjectives’ linguistic origin). According to Ferguson’s (2009) standards, this model has a strong effect size (R² = 0.6381).

Table 7.

Final Mixed-Effect Regression Model for ‘Basque Speaker’ Group.

	Estimate	SE	t	p
Adj gender = masc	-2.9816	0.3193	-9.338	6.56e-05
Ling origin = Basque	0.0279	0.3094	0.090	.930
Adj gender = masc + Ling origin = Basque	0.1676	0.4278	0.392	.704

The significant effect of gender morpheme was also confirmed by the ANOVA (X²[1] = 184.7156, p = < 2e-16), illustrated by Figure 3: the use of feminine morpheme with female referents is perceived sounding as statistically more Basque speaker, natural, and someone with higher level of education, regardless of the linguistic origin of the adjectives (Basque vs. Spanish).

Figure 3.

Significant effect: gender morpheme.

Focusing on the ‘Linguistic factor’ group, results from the mixed-effect regressions presented in Table 8 indicate a significant effect for adjectives’ linguistic origin (no significant interaction between the gender morpheme used and adjectives’ linguistic origin). This model was found to have a strong effect size (R² = 0.8256) based on Ferguson (2009).

Table 8.

Final Mixed-Effect Regression Model for ‘Linguistic Factor’ Group.

	Estimate	SE	t	p
Adj gender = masc	-0.4244	0.4099	-1.036	.321
Ling origin = Basque	-3.8333	0.4113	-9.321	7.89e-07
Adj gender = masc + Ling origin = Basque	0.5994	0.5594	1.072	.305

The significant effect for adjectives’ linguistic origin was also confirmed by the ANOVA (X²[1] = 158.4547, p ⩽ 2e-16), and is illustrated in Figure 4: adjectives with a Spanish origin receive statistically higher ratings, regardless of the gender morphology used with female referents. This implies that Spanish-originated adjectives are perceived as receiving a significantly bigger effect of Spanish than Basque-originated adjectives.

Figure 4.

Significant effect: adjectives’ linguistic origin.

Finally, the mixed-effects logistic regression and ANOVA for the ‘Social profile’ factor suggest that there is no significant difference on gender use based on adjectives’ linguistic origin.

Discussion

The study’s first research question investigated the morphological variation of adjectives based on the gender of the antecedent in Mundaka Basque. The SCT results revealed categorical production: all participants consistently used the feminine morpheme (-ie) with female referents and the masculine morpheme (-ue) with male referents. This agreement was found for both Spanish-originated and native Basque-origin adjectives, contradicting the widespread assumption that Spanish-style GGA in Basque is restricted to loanwords (Laka, 1996; Trask, 2003). Taken together, the categorical production in Mundaka, paralleled by Ondarroa Basque results (Basterretxea Santiso et al., 2026), challenges the long-held assumption that the Basque language lacks GGA entirely (Euskaltzaindia, 1991, 2002). Evidence from these two Western Basque varieties thus confirms the presence of such agreement and suggests the phenomenon is not marginal or limited exclusively to oral production.

Crosslinguistic evidence strongly supports the proposition that GGA systems can be transferred due to intense language contact. The literature differentiates between the retention of borrowed morphology (typical lexical borrowing) and true structural transfer. In typical lexical borrowing, morphology is retained solely on the loanword itself. For instance, Spanish-English bilinguals retain Spanish gender morphology (-o/-a) on Spanish adjectives inserted into English, such as It’s a really bonita (‘pretty-F.SG’) house (Woolford & Myers-Scotton, 1999). Similarly, Yucatec Maya shows that highly bilingual speakers retain Spanish agreement on loanwords, but native Yucatec adjectives remain invariable (Bricker, 1986).

The categorical rejection of masculine forms for female referents in Mundaka suggests that the feminine morpheme (-ie) has transitioned from a sporadic loan-feature into a highly salient, marked category within the local grammar. Conversely, the masculine (-ue) continues to function as the structural default (or 0-marked form), maintaining its role as the ‘neutral’ exponent inherited from the traditionally genderless Basque system. This structural asymmetry aligns with global typological patterns in language contact, where the emergence of gender often begins with the introduction of a marked feminine category against a pre-existing masculine or neutral base (cf. Aikhenvald, 2016; T. Stolz, 2012). In Mundaka, this markedness is reinforced by the social value attributed to the feminine form; because -ie is perceived as more ‘natural’ and ‘educated’ for women, it carries a higher functional load, forcing a mental realignment where gender must be indexed specifically for female entities, while the masculine remains the underspecified default.

Consequently, the finding that Spanish GGA morphology is transferred onto native Basque adjective stems represents a sophisticated case of structural borrowing that challenges traditional hierarchies of contact-induced change. This aligns with Thomason and Kaufman’s (1988) Borrowing Scale, which posits that structural changes to native elements are possible under conditions of intense and long-term contact. Specifically, this transfer of inflectional morphology onto native stems contradicts the widely cited ‘hierarchy of borrowability’ (Matras, 2007), which typically identifies inflectional categories as the most resistant to external influence. However, the Mundaka data align with crosslinguistic precedents confirming that core functional domains are, in fact, permeable under intense contact. For instance, ‘gender-copying’ has been documented in Chamorro (T. Stolz, 2012) and Maltese (C. Stolz, 2009), and morphosyntactic gender features from Standard Italian were mapped onto native functional categories in Piedmontese dialects (Maiden, 1995). Furthermore, core syntactic structures in Scottish Gaelic—traditionally a verb-subject-object (VSO) language—have even shifted toward subject-verb-object (SVO) patterns under the influence of English (Stenson, 1993). These parallels, alongside the gender conflict resolution strategies observed in Spanish-Basque mixed DPs (Parafita Couto et al., 2015), confirm the permeability of core functional domains to external morphosyntactic features. In this light, the Mundaka Basque data represent more than a localized change in adjective morphology; they signify a fundamental architectural restructuring where gender—a category traditionally absent from the language—has been integrated into the native morphosyntactic template.

The Mundaka data support the central hypothesis proposed by Basterretxea Santiso et al. (2026) regarding the nature of contact-induced GGA in Basque. Following the terminology employed by Di Garbo and Miestamo (2019) when exploring GGA in language contact situations, the emergent Basque GGA system is characterized as ‘conditional’ rather than ‘absolute’, meaning morphological variation is contingent upon the specific adjective employed. This demonstrates that speakers of these two varieties do not adopt the Spanish rule requiring universal adjectival inflection for gender and apply it uniformly to their native Basque adjectives. Rather, the system is lexically restricted. The distribution of native Basque adjectives, detailed in Table 9, provides empirical validation for the conditional nature of the transfer by showing which stems vary according to the gender of the referent.

Table 9.

Division of Basque Adjectives Based on Their (Im)possibility to Produce GGA.

	Group 1	Group 2	Group 3
Explanation	Spanish-originated adjectives ending in -o offer the possibility to produce GGA.	Basque adjectives ending in -o offer the possibility of producing Spanish-style GGA for misassuming that -o corresponds to the masculine.	Basque adjectives that do not end in -o would not offer the possibility of producing Spanish-style GGA.
Examples	feo/a ‘ugly’, guapo/a ‘handsome’, katoliko/a ‘catholic’, konfliktibo/a ‘problematic’, listo/a ‘smart’, majo/a ‘nice’, parrandero/a ‘party animal’, moreno/a ‘dark-haired’, ofendido/a ‘victim’, pelmo/a ‘annoying’, sinpatiko/a ‘kind’, tonto/a ‘stupid’.	gizajo/a ‘poor’, larrizto/a ‘disgusting’, potxolo/a ‘plump’, totolo/a ‘fat’, txotxolo/a ‘dumb’.There are, however, some Basque adjectives that end in -o that would not offer the possibility of using Spanish-style gender marking: babo ‘stupid’, goxo ‘sweet’, geldo ‘inactive’, and zoro ‘crazy’. These adjectives were not included in our methodology, but we have not observed (with locals, media, and texts in Basque) the use of Spanish-style gender agreement with them.	handi ‘big’, txiki ‘small’, polit ‘pretty’, itsusi ‘ugly’, ahul ‘weak’, azkar ‘intelligent’.

The second research question examined the implicit attitudes of Mundaka Basque speakers toward the use of gender morphemes with female antecedents using an MGT. The results show a clear social judgment favoring feminine morphology. The use of feminine morphology with female referents was perceived as significantly more characteristic of Basque speakers, more natural, and indicative of a higher level of education than the use of masculine morphology. This strong preference held irrespective of the adjective’s linguistic origin (Spanish or Basque), aligning with the attitudes reported for Ondarroa Basque (Basterretxea Santiso et al., 2026). Conversely, regarding the ‘Linguistic factor’, no attitudinal differences emerged based on the gender morpheme used: both feminine and masculine forms were judged similarly in terms of reflecting Spanish influence. Furthermore, no significant age effects were observed: neither the feminine nor the masculine morpheme was associated with younger or older speakers, mirroring the results from Ondarroa Basque (Basterretxea Santiso et al., 2026).

The study revealed key differences between Mundaka and Ondarroa, stemming directly from the contrast in their sociolinguistic profiles: Mundaka experiences a high concentration of tourism and seasonal residency, subjecting it to higher external, Spanish-dominant contact pressure and linguistic influence than the more stable Ondarroa, which is characterized by significantly lower external pressure. In terms of perception, Mundaka speakers judged Spanish-origin adjectives as exhibiting significantly more Spanish influence than Basque-origin adjectives, which contrasts with Ondarroa, where adjective origin did not affect perceived Spanish influence (Basterretxea Santiso et al., 2026). Regarding self-reported production rigidity, Mundaka participants demonstrated high consensus for feminine agreement and nearly categorical rejection of masculine agreement with female referents. Conversely, Ondarroa participants exhibited less consensus regarding feminine agreement production and showed a lower rejection of masculine agreement (Basterretxea Santiso et al., 2026).

In Mundaka, where Spanish contact is intense and highly salient, speakers display a heightened awareness of the source language of borrowed items. This elevated contact consciousness reflects an ongoing social negotiation of linguistic boundaries (Giles, 2016; Myers-Scotton, 1993). Mundaka speakers’ acute sensitivity to an adjective’s origin renders the use of a Spanish-derived form a socially meaningful act, indexing an underlying negotiation over the legitimacy of Spanish incorporation into the Basque domain. By evaluating Spanish-origin adjectives as conveying ‘significantly more Spanish influence’, speakers reaffirm the notion that Spanish remains an external linguistic force requiring continual monitoring at the lexical level.

The establishment of a rigid sociolinguistic norm in Mundaka—evident in the strong consensus for feminine agreement and categorical rejection of masculine agreement with female referents—constitutes a distinct form of social negotiation. By uniformly rejecting the masculine form, Mundaka speakers delineate a strict boundary around the emergent conditional gender feature. They signal a Basque identity that recognizes the gender distinction (introduced through Spanish contact) but chooses to enforce it rigorously, thereby resisting the casual influence that might otherwise lead to simplification through generalized masculine usage. This contrasts with Ondarroa, where the lack of parallel distinctions (weaker consensus and lower rejection rates) suggests that Spanish loanwords have been more fully naturalized within the local Basque vernacular, and the intensity of social negotiation around these features is reduced. In Mundaka, the continuous and visible presence of Spanish keeps this negotiation active, pushing speakers to articulate clear identity stances regarding which forms are legitimate (feminine agreement) and which are rejected (masculine) within their Basque repertoire.

The differing levels of consensus in self-reported production demonstrate how swiftly and strictly a new sociolinguistic norm can crystallize in contexts of sustained contact. Despite intense Spanish influence, Mundaka Basque has developed a highly rigid norm for conditional feminine agreement. This strictness functions as a social boundary marker (Labov, 1972; Le Page & Tabouret-Keller, 1985). Through unanimous acceptance of the feminine form and categorical rejection of the masculine, speakers make an overt identity choice: they actively repudiate the structural ‘error’ that could be attributed to pervasive Spanish exposure. This consensus serves as an act of identity enforcement, establishing the feminine form as the only acceptable expression of a committed Basque identity in this grammatical domain. By contrast, Ondarroa appears slower to generalize and enforce this emergent agreement feature community-wide. The lower consensus suggests that the gender distinction is less structurally entrenched or less socially salient there, particularly given the greater acceptance of the historically non-agreeing masculine form with native Basque adjectives.

Taken together, these patterns show that although both Bizkaian communities exhibit structural innovation through conditional gender agreement, the sociolinguistic meaning of that change diverges sharply. In Mundaka—where external Spanish pressure is constant—the transferred agreement feature is mobilized as a rigid boundary marker and a deliberate identity stance, functioning to police the Basque system against contact-induced simplification. In contrast, in Ondarroa’s comparatively stable linguistic environment, the same feature diffuses more gradually and with weaker enforcement.

Conclusion

The present study, drawing on data from Mundaka and comparative findings from Ondarroa, fundamentally challenges the long-held assumption that Basque lacks GGA (Euskaltzaindia, 1991; Trask, 2003). Our findings provide robust evidence, parallel to that of Basterretxea Santiso et al. (2026) for Ondarroa Basque, that a Spanish-style conditional GGA system has been established in these two Western Basque varieties. Crucially, this agreement is not restricted to Spanish-originated adjectives but extends to a subset of native Basque-origin adjectives. This demonstrates that the phenomenon constitutes an instance of deep structural borrowing at the level of inflectional morphology, rather than merely lexical retention. The analysis confirms the system is conditional (Di Garbo & Miestamo, 2019) and lexically restricted, primarily to adjectives ending in -o.

This research makes a critical contribution to Basque linguistics by shifting the focus from whether gender agreement exists to how and why it is structurally implemented and socially enforced. On the one hand, the definitive documentation of Spanish-style GGA transferred to native Basque adjective stems (e.g., gizajo/a, totolo/a) refutes the prevailing view of Basque’s categorical resistance to gender. This provides direct evidence of structural permeability, aligning with Thomason and Kaufman’s (1988) Borrowing Scale. On the other hand, the study empirically supports that linguistic outcomes in the Basque Country vary based on the degree of contact and local ideological factors (Amorrortu, 2003). The differential enforcement of the same structural feature across two proximate communities under varying contact intensity offers key theoretical insight:

The contrast proves that the adoption and enforcement of a borrowed grammatical feature are governed by social negotiation rather than solely by linguistic availability. Mundaka’s enforcement of feminine agreement as a rigid boundary marker (Labov, 1972; Le Page & Tabouret-Keller, 1985) is a direct result of pervasive contact pressure, demonstrating that the community mobilizes the transferred feature as a conscious identity choice to police its language against contact-induced simplification.

The finding confirms that the resulting structural change is conditional (Di Garbo & Miestamo, 2019) and is mediated by Communities of Practice (Eckert, 2000) that determine the specific lexical stems (i.e., adjectives) that carry the social load.

Based on the findings of structural permeability and strong social enforcement in the contact zones, two primary predictions are offered. (1) Given the high consensus and social salience of the conditional gender distinction in Mundaka, the lexical generalization of the -o/-a opposition is predicted. Adjectives ending in -o that currently resist agreement (e.g., goxo) may begin to adopt the feminine suffix as the social norm strengthens and speakers align their production with the desired pattern. (2) The divergence between Mundaka and Ondarroa will likely increase. Mundaka is expected to consolidate the conditional agreement feature as a mandatory social marker, while Ondarroa may retain greater inter-speaker variability and exhibit slower change.

To confirm and expand these conclusions regarding the conditional emergence of GGA in Basque, future research is imperative across three key areas. Exploring other Western and non-Western Basque varieties (including Basque-French contact) with diverging sociolinguistic situations. In addition, broadening the currently homogeneous participant profiles (age, linguistic background, educational level) to include diverse sociolinguistic groups. Finally, empirically confirming the possibility of producing GGA with the adjectives in Group 3 in Table 9 to fully explore the conditional nature and lexical restrictions of this emergent system.

Footnotes

Appendix 1

Female antecedent

Masculine antecedent (distractors)

ORCID iDs

Ager Gondra

Gorka Basterretxea Santiso

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Notes

Author Biographies

Ager Gondra is an Associate Professor of Linguistics at the University of Miami whose research specializes in bilingualism, language contact, and morphosyntax. Within the Basque context, he investigates morphosyntactic variability across generations and how institutionalization reshapes the linguistic ideologies of traditional speakers, while his Spanish-focused research examines cross-generational variation and dialectal leveling.

Gorka Basterretxea Santiso completed his PhD in Hispanic linguistics at Georgetown University. His main area of research is sociolinguistics and language contact in the Basque Country and the US (production patterns and linguistic attitudes). He has previously published his research on academic journals such as Studies in Hispanic and Lusophone Linguistics, International Journal of Multilingualism, or Open Linguistics.

Sara Gómez Seibane is a Professor of Spanish Language at the University of La Rioja. A leading expert in linguistic variation and change, her research specializes in Spanish in contact with the Basque language. She also co-directs the COREC project, dedicated to developing a comprehensive oral corpus of Spanish in contact with other languages.

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