The present study is an attempt to explore the effect of one of the pragmatic elements of discourse (namely the conceptualizable agent) on overpassivization of English unaccusative verbs. Through employing the questionnaire originally used by Ju, (2000), 206 Iranian intermediate and advanced English majors were asked to choose the more grammatical form (active or passive) in target sentences with unaccusative verbs. Each target sentence was embedded in two different contexts expressing external and internal causation. The participants' performance supported the hypothesis that unaccusatives were overpassivized more when the discourse context offered a conceptualizable agent, and that monadic unaccusative verbs were passivized more than dyadic ones. The learners recognized conceptualizable agents offered by the discourse context and their judgments on sentence acceptance were influenced by these agents. Since, in the literature, other researchers like Ju (2000); Oshita (1997); Yip (1995); and Zobl (1989) reported that many non-native English learners cross- linguistically over-passivize unaccusative verbs, it provided additional support for the claim that these errors are language universal rather than language specific. Thus, this paper argues against a purely syntactic analysis of interlanguage errors such as overpassivization and talks in favor of an approach that takes pragmatic factors into account as well.
