The time course of argument reactivation revealed: using the visual world paradigm

Previous research has found that the single argument of unaccusative verbs (such as fall) is reactivated during sentence processing, but the argument of agentive verbs (such as jump) is not (Bever & Sanz, 1997; Friedmann, Taranto, Shapiro, & Swinney, 2008). An open question so far was whether this difference in processing is caused by a difference in thematic roles the verbs assign, or a difference in the underlying syntactic structure. In the present study we tease apart these two potential sources. In order to achieve this, we included a set of verbs (like sparkle) which are equal to unaccusative verbs in the thematic role they assign to their argument, but equal to agentive verbs in the syntactic status of their argument (henceforth mixed verbs). As a method we used the visual world paradigm as this enables us to measure processing of the sentences continuously. This method also allowed us to test another hypothesis, namely the hypothesis that not only the argument of unaccusative verbs is reactivated during processing, but also the argument of agentive verbs. This reactivation is expected as the result of integrating the verb and its argument into one representation. In our experiment, participants listened to sentences including one of the three types of verbs. While listening, they viewed a visual display in which one of four objects was strongly related to the argument of the verb (wood-saw). The gaze record showed that the eyes moved to the related object (saw) upon presentation of the argument (wood). More interestingly, the eyes moved back to the related object upon presentation of the verb (fell). We found that looks to the related object increase only late after verb offset for unaccusative verbs, replicating the findings of previous research. We also found a rise in looks to the related object in agentive verbs, but this rise took place much earlier, starting slightly after verb onset. Finally, we found that mixed verbs pattern in processing with agentive verbs. We conclude that the argument of the verb is always reactivated, independent of verb type. In addition, the timing of integration differs per verb type and depends on the syntactic status of the argument and not on the thematic role that is assigned to the argument.