Abstract

A stream of sensory information is organized into discrete temporal units through event segmentation. On the basis of several studies measuring participants' explicit decisions about event boundaries, some theorists suggest that this segmentation is induced by increased unpredictability. Since this approach cannot describe the segmentation of unfamiliar events, we assumed that event segmentation might be perceptually driven. We hypothesized that when a new event-relevant object is represented, it triggers event segmentation. In addition to explicit decisions, we measured memory performance, since it has previously been found to be a strong indicator of event segmentation. We presented simple videos to the participants in which geometric objects were flashing consecutively while an unpredictable change occurred. In the New Object condition flashing objects were replaced, while in the Same Object condition one non-kind-relevant feature of the objects was changed. In Experiment 1 the participants' task was to press a button when they detected a meaningful change in the stimuli. In line with the predictability-based theories, we found that both changes triggered the detection of an event boundary. To contrast our hypothesis with the predictions of earlier theories, in Experiments 2 and 3 memory accuracy was measured using the stimuli of Experiment 1. We only found a significant change in memory accuracy in the New Object condition, which suggests that the appearance of an event-relevant object can induce segmentation on its own, and indicates that the explicit-decisions methodology might lead to the improper conclusion that event segmentation is solely based on predictability.