This study investigates whether suggestion of external causation in contexts plays a role in English L2 overpassivization errors on unaccusative verbs. Based on lexical semantic theories and considering the effect of inferencing, it is hypothesized that; 1) Such errors are sensitive to verb unaccusativity strength which is presupposed in the study; 2) The degree of overpassivization in the context with strong suggestion of external causation differs significantly from that in contexts with weak suggestion of external causation; 3) As learners become more proficient in L2, the more semantic knowledge they possess, the less they are affected by a cognitive factor such as inferencing. This thesis thus contributes to theorizing the overpassivization issue by providing empirical evidence in favor of a Causativization account.
