The sandwich effect in L3 acquisition: A look at the Catalan and Spanish grammars of highly advanced speakers of L3 English

Aims and objectives: This study examines the extent to which the acquisition of a highly advanced third language (L3) will affect previously (early) acquired languages. We directly test the main tenets of the differential stability hypothesis. Design/method/approach: We test 72 Catalan-Spanish bilinguals divided across four groups using two dimensions: (a) order of acquisition and (b) proficiency/exposure in L3 English. We administered two self-paced reading tasks (one in Catalan and the other in Spanish) to explore their processing of negative concord items. Data analysis: Using generalized linear mixed-effects models, we analysed the effect English had on the processing of negative concord items in Catalan and Spanish in three different conditions of interest. Findings/conclusions: The results partially confirm the tenets of the differential stability hypothesis (DSH). We show that first language (L1) and second language (L2) are differentially affected by the acquisition of an L3. We further show that there are different degrees of vulnerability for different syntactic contexts in an L2. We propose a novel effect in the study of L3 regressive effects that can complement the tenets of the DSH: the sandwich effect in L3 acquisition. Originality: The study provides the first empirical investigation of the tenets of the DSH. Significance/implications: This study offers a new effect in L3 acquisition and we put forward how we can test it and propose new directions to explore regressive transfer effects.