Who when where: an experimental test of the event-indexing model.

We tested the event-indexing model proposed by Zwaan, Langston, and Graesser (1995). Participants read narratives containing target sentences that involved situational shifts. Independently of each other, continuity and shifting of the protagonist, time, and location dimensions were varied. In Experiment 1, reading times of the target sentences increased for protagonist shifts and temporal shifts, whereas the effect of spatial shifts was weak. Moreover, an interaction of protagonist shifts and spatial shifts was found. These results were replicated in Experiment 2, which also revealed strong effects of these situational shifts on coherence ratings that participants gave immediately after reading each target sentence. Experiment 3 addressed the interaction of protagonist shifts and spatial shifts, showing that it may be due to the differential involvement of unexplained protagonist motions. These experimental results support the processing load predictions of the event-indexing model and extend previous correlational results.