Event boundaries in perception affect memory encoding and updating

Abstract

Memory for naturalistic events over short delays is important for visual scene processing, reading comprehension, and social interaction. The research presented here examined relations between how an ongoing activity is perceptually segmented into events and how those events are remembered a few seconds later. In several studies, participants watched movie clips that presented objects in the context of goal-directed activities. Five seconds after an object was presented, the clip paused for a recognition test. Performance on the recognition test depended on the occurrence of perceptual event boundaries. Objects that were present when an event boundary occurred were better recognized than other objects, suggesting that event boundaries structure the contents of memory. This effect was strongest when an object's type was tested but was also observed for objects' perceptual features. Memory also depended on whether an event boundary occurred between presentation and test; this variable produced complex interactive effects that suggested that the contents of memory are updated at event boundaries. These data indicate that perceptual event boundaries have immediate consequences for what, when, and how easily information can be remembered.

Figure 1

Illustration of recognition tests. After participants pressed the space bar to begin a trial, a fixation cross appeared in the center of the screen and gaze position calibration was checked. After two seconds the clip started and the old object was presented. Five seconds after the old object was presented, the clip stopped for an object test and the old object and a different type object were presented as the test alternatives. The trial ended when the participant answered the question. To provide the participant with feedback and to reinstate the context of the film, on the next trial the clip was restarted at a point ten seconds prior to the time it was stopped (a). On several trials participants were give a question about an activity or event that just occurred in the clip (b). In Experiment 2, memory for conceptual information about the objects was tested by asking participants to select the type of object that was just in the clip (c). In Experiment 3, memory for perceptual information was tested by asking participants to select between the old object and an object of the same type (d). All movies and images were displayed in full color.

Figure 2

Four object test conditions resulting from the relationship between object presentation and event boundaries. Object tests were coded along two factors indicating whether an event boundary occurred during the time the old object was on the screen (indicated by a gray rather than white box), and whether an event boundary occurred after the old object disappeared from the screen, but before the recognition test (indicated by a broken, rather than solid line). If no event boundaries occurred during object presentation or during the delay between presentation and test, then the object was in the nonboundary object, current event condition (Object A). If a boundary occurred during presentation, but not during the delay, then the object was in the boundary object, current event condition (Object B). If a boundary occurred during the delay, but not during object presentation, then the object was in the nonboundary object, previous event condition (Object C). If boundaries occurred during both presentation and the delay between presentation and test, then the object was in the boundary object, previous event condition (Object D).

Figure 3

Mean estimates of accuracy (a) and response times (b) for tests of an average old object in the eight object test conditions defined by fixation and event boundaries in Experiment 1. The dashed line in (a) indicates chance accuracy. Accuracy and response times were estimated in the manner described in the Methods section. For all figures, error bars indicate the 95% confidence intervals around the mean.

Figure 4

Mean estimates of accuracy (a) and response times (b) for conceptual tests of an average old object in the eight object test conditions defined by fixation and event boundaries in Experiment 2.

Figure 5

Mean estimates of accuracy (a) and response times (b) for perceptual tests of an average old object in the eight object test conditions defined by fixation and event boundaries in Experiment 3.

Figure 6

The effects of the delay-boundary, presentation-boundary, and their interaction on accuracy varied across experiments. Estimated accuracy for objects from the current event and for objects from previous events for the different types of tests (a). Estimated accuracy for boundary objects and nonboundary objects for the different types of tests (b). Estimated accuracy for the four conditions described by the presentation-boundary and delay-boundary factors, collapsed across fixation and illustrated for the three different types of tests (c). Estimated values were calculated in the manner described in the Methods section. The dashed line in each panel indicates chance performance.

Figure 7

Overall estimated response times in the eight conditions defined by the delay-boundary, presentation-boundary, and fixation conditions, collapsed across experiments (a). The effect of fixation on response times depended on the delay-boundary factor and varied across experiments, illustrated here with the estimated response times (b).