L3 Regressive Transfer: A Study of Null Objects in the Basque and Spanish Grammars of Advanced L3 English Speakers

ABSTRACT Regressive transfer has been a subject that has not been extensively researched in the field of third language acquisition. This study aims to examine the extent to which a highly advanced knowledge of a third language (L3) affects the first language (L1) and the second language (L2) of early bilinguals in light of the Differential Stability Hypothesis (DSH) and the sandwich effect . Twenty‐one ( n = 21) Basque‐Spanish early simultaneous bilinguals with a minimum C1 proficiency in English were divided into a Spanish‐dominant and a Basque‐dominant group. Using an online self‐paced reading task (SPRT) and an offline grammaticality judgment task (GJT), the study examined participants’ knowledge and processing of null object constructions (NOCs), a linguistic structure that differs in the three languages at play (Basque, Spanish, and English). Based on the DSH, the expectation is that the L2 of both groups will be more affected by English than the L1. Regarding the sandwich effect , the expectation is that the L2 will be more vulnerable to influence from the L3 when this L3 and the L1 share the same representation of the linguistic structure being analyzed, NOCs in this case. Results from the Basque‐dominant group provide evidence of negative transfer supporting the DSH in both tasks, while the Spanish‐dominant group performed better in their L2 than in their L1.