Theoretical implications of research on bilingual subject production: The Vulnerability Hypothesis
Authors: de Prada Pérez Ana 
Published: March 2018

In this paper we propose a new hypothesis for the formal analysis of cross-linguistic influence, the Vulnerability Hypothesis (VH), with the support of data from subject personal pronoun use in Spanish and Catalan in Minorca, and contrast it to the Interface Hypothesis (IH). The VH establishes a categorical–variable continuum of permeability, that is, structures that show variable distributions are permeable while those that exhibit categorical distributions are not. To test the predictions of the VH, Spanish language samples were collected from 12 monolingual Spanish speakers, 11 Spanish-dominant bilinguals, and 12 Catalan-dominant bilinguals, and Catalan language samples from 12 Catalan-dominant speakers. Following a variationist comparative analysis, 4,466 first person singular (1sg) and 1,291 third person singular (3sg) tokens were coded for speech connectivity, verb form ambiguity, and semantic verb type. The language-external variable included in the analysis was language group (Spanish monolinguals, Spanish-dominant bilinguals, Catalan-dominant bilinguals, and Catalan controls). Results indicated that speech connectivity is the highest ranked variable in the Spanish control group (most categorical variable), while ambiguity and verb type are ranked lower, with only ambiguity reaching significance. The VH would, therefore, predict bilinguals would be similar to monolinguals in the most categorical variables, in this case, speech connectivity. This is in contrast to the IH, which would predict bilinguals would exhibit difficulty with the pragmatically driven distributions (e.g. speech connectivity), while they would show no contact effects or lesser effects with distributions at the lexico-semantic interface with syntax (e.g. verb form ambiguity and verb type). The prediction of the VH bears out in our data. Bilinguals do not differ with respect to speech connectivity. Ambiguity, on the other hand, is no longer significant in the bilingual groups and verb type reaches significance with 1sg (and not with 3sg) subjects. These results are discussed, redefining the concepts of convergence and simplification from language contact research to adapt to the variationist analysis used. Simplification is specified as the reduction of lower ranked predicting variables, while convergence is defined as an increase in parallels across languages with respect to the variables that are significant, their effect size (variable ranking), and the direction of effects (constraint ranking). Regarding language group, it was not returned as significant in 1sg data. Thus, the groups did not differ in their rates of overt pronominal expression. Differences, however, emerged across groups in the 3sg data, where bilinguals used significantly more overt pronominal subjects than monolinguals do. This paper contributes to current discussions in the fields of language contact, second language acquisition, and bilingualism, introducing a new hypothesis and contrasting it with the IH. In addition, it contributes to variationist approaches by examining a novel community of bilingual speakers.