Unergative verbs assign the agent theta role to subjects whereas unaccusative verbs occur with theme subjects. Theory suggests that, unlike subjects of unergative verbs, theme subjects of unaccusative verbs are merged in the post-verbal internal argument position and moved to the pre-verbal external argument position. In a cross-modal lexical priming experiment, we tracked (re‑)activation patterns of the subject in sentences with imperfective and perfective unergative and unaccusative verbs in Bosnian/Croatian/Serbian (BCS). We investigated the interplay between unaccusativity and verbal aspect. Our findings are that the subject of perfective unaccusative verbs is (re‑)activated post-verbally, at the gap position, whilst this is not the case for unergative verbs and imperfective unaccusative verbs.
Čordalija et al. (Mon,) studied this question.