Do not cross the line: heuristic spatial updating in dynamic scenes.

In two experiments, we examined the spatial integration of two viewpoints onto dynamic scenes. We tested the spatial-alignment hypothesis (which predicts integration by alignment along the shortest path) against the spatial-heuristic hypothesis (which predicts integration by observation of the left-right orientation on the screen). The stimuli consisted of film clips comprising two shots, each showing a car driving by. In Experiment 1, the dynamic scenes were ambiguous with regard to their interpretation: The cars could have been driving either in the same or in opposite directions. In line with the spatial-heuristic hypothesis, participants responded with "same direction" if the cars shared a screen direction. In Experiment 2, environmental cues disambiguated the dynamic scenes, and the screen direction of the cars was either congruent or incongruent with the depicted environmental cues. As compared with congruent dynamic scenes, incongruent dynamic scenes elicited prolonged reaction times, thus suggesting that heuristic spatial updating was used with congruent stimuli, whereas spatial-alignment processes were used with incongruent stimuli.