Visual memory for natural scenes:

automatic + task dependent components

Alan Robinson and Jochen Triesch

VSS 2004 Poster Abstract

Are the contents of visual memory influenced by a subject's task? Our previous work using natural tasks in virtual reality has shown strong task effects, coupled with minimal memory usage. Hollingworth (2003) has shown, however, that people can encode a great deal of information when viewing natural scenes. In this work we show that even when people encode a lot of detail there are still strong task effects.

We conducted 2 experiments using a novel change-detection paradigm. In both experiments subjects completed 2 tasks; the first was to describe objects in a set of natural images, reporting a specific property of each object when a crosshair appeared above it, such as its name or dominant color. The other task was viewing a modified version of each scene, and detecting which of the previously described objects had changed. Subjects were split into separate groups, which described the same objects, but different aspects (name, or dominant color). In Experiment 1, subjects were told they were in a memory experiment and performed the change detection task for each image immediately after describing the objects in that image. In Experiment 2, subjects finished describing all images before being informed that we were studying memory and performing the change detection task.

Surprisingly, subjects in both experiments showed comparable levels of overall change detection, even though in Experiment 2 the memory task was unexpected and memory contents were probed after a 1-5 minute delay. We also found task effects, but only in Experiment 2. When subjects described the color of objects, their ability to detect color changes was increased by 16%, whereas when they named the objects, their ability to detect object additions increased by 22%. We conclude that people automatically encode a surprising amount of visual details when viewing natural scenes, but the details encoded depend strongly on people’s task, and their understanding of that task's overall demands.

Full Poster Download

1 page version formatted for 8.5x14" (or larger) paper size. [PDF; 1,448 KB]
4 page version reformatted for 8.5x11" paper size. [PDF; 314 KB]

Stimuli Demo

This JAVA applet demonstrates a single trial from experiment 1. Each crosshair is shown for 2 seconds. After saying the name or color of the object, the subject immediately clicks the mouse button to advance to the next crosshair. After seeing 8 crosshairs individually on a scene, the subject is immediately tested on their change detection ability. All crosshairs are displayed on the modified scene and the subject is instructed to click on the one corresponding to the change. Trials in experiment 2 are the same, except for the several minute delay between viewing the original scenes and then detecting changes in the modified scenes.

Acknowledgments

We thank Ronald Rensink for donating the stimuli we used in this research, and Cherie-Marie Vitartas for running our subjects. This work was supported by the University of California Academic Senate, San Diego Division, under grant RC142C-TRIESCH.

Return to publications

Return to Alan's vision page