Event Segmentation of Agent Interactions: Comparing the Whole with Its Parts

Event Segmentation of Agent Interactions: Comparing the Whole with Its Parts Bryan L. Koenig 1,2 (koenigbl@ihpc.a-star.edu.sg) David Pautler 1 (pautlerd@ihpc.a-star.edu.sg) Jonathan S. Herberg 1 (herbergjs@ihpc.a-star.edu.sg) Kum Seong Wan 1 (kswan@ihpc.a-star.edu.sg) Brian Monroe 1,2 (monroebm@ihpc.a-star.edu.sg) Edwin Wirawan 1 (wirawane@ihpc.a-star.edu.sg) Institute of High Performance Computing, A*STAR National University of Singapore, Singapore finds that motion cues are strongly correlated with breakpoints (Hard, Tversky, & Lang, 2006). Indeed, simple computational models can use seven motion cues to identify agentic motives in animations of two moving figures with accuracy levels similar to those of human observers (Blythe, Todd, & Miller, 1999). Absolute and relational motion cues can be quite complicated in such stimuli, which sometimes have three figures moving in relation to one another and the background context. We wondered how human observers incorporate information from each agent when viewing stimuli of multiple agents interacting. In order to address this question, we had participants in a default condition segment into meaningful events a multiple-figure animation previously shown to elicit compelling perceptions of social interactions (Heider & Simmel, 1944). Other participants in focus conditions segmented the same animation but only for events meaningful for the figure specific to the condition. We compared participants’ segmentation patterns across conditions to test whether observers by default process all events relevant for all agents. Alternatively, perhaps by default observers systematically miss events that are important for some agents or notice events that would be overlooked when focusing on any one agent. We now consider evidence that suggests each of these is plausible. Research in which participants segment perceived events for animations of moving figures suggests that movement features such as sudden acceleration elicit the perception of event boundaries (Hard, et al., 2006; Zacks, 2004). For such stimuli, participants even indicate breakpoints at similar time points when viewing multiple-agent animations both forward and backward, and these time points strongly correlate with objective movement features (Hard, et al., 2006). Such findings provide support for the notion that observers incorporate all movement cues when perceiving events, which we label the objective movement hypothesis. According to this hypothesis, observers perceive ongoing interactions in terms of all movement Abstract How do observers perceptually organize the events of individual agents when observing interactions among them? Do they readily perceive all events? Do they selectively perceive some events but not others? Do they see events overlooked by observers focusing on the individual agents? To explore these questions, participants viewed the Heider and Simmel (1944) animation, which shows three moving figures and elicits strong impressions of interacting agents. Participants in the default condition segmented the animation into meaningful events. Those in focus conditions did likewise, but focusing on one of the figures. Results indicate that participants in the default condition disregarded many events identified in the focus conditions, but identified only one event missed by focus-condition participants. These findings suggest that observers of interactions do not encode all events or gain additional insight by “seeing the big picture”; rather, they selectively perceive some events at the cost of overlooking others. Keywords: Social perception; event segmentation; unit formation; perspective taking; movement cues; animation. Introduction Much research has centered on how observers perceive and understand the actions of individual agents. In a typical experimental task, participants view an activity such as washing dishes and mark when, in their judgment, a meaningful event ends and another begins. These marked time points are referred to as breakpoints, and participants substantially agree about their placement (e.g., Zacks, Tversky, & Iyer, 2001). Breakpoint placement is not an arbitrary consequence of the segmentation task. Brain activity selectively occurs during mere observation at the same time points that participants identify as breakpoints during a subsequent segmentation task (Zacks, Swallow, Vettel, & McAvoy, 2006). These findings suggest that event segmentation reflects the perceptual structure of events. Other research on how observers perceptually segment the events of animations of multiple interacting figures