Second language learners of English occasionally overuse be with unaccusative verbs, resulting in non-target-like sentences such as *An accident was happened. This study investigates one of the key hypotheses addressing this phenomenon—the Perfective Auxiliary Marker Hypothesis (Yusa, 2002, 2003)—which posits that overused be functions as a perfective auxiliary. To test a logical prediction derived from this hypothesis—that be should not co-occur with have (e.g., *A beautiful rainbow has been appeared in the sky)—an acceptability judgment task was administered to 33 Japanese-speaking learners of English and 28 native English speakers as controls. The results, both at the group and individual levels, reveal that L2 learners failed to reject constructions where be and have co-occurred. This finding aligns with Hirakawa (2006), reinforcing the argument that overused be does not function as a perfective auxiliary in L2 grammars. [Katooka, K. & Hokari, T.]
