Taking a picture apart: Memory for backgrounds and objects in scene photographs

Jennifer S DiMase, Aude Oliva, & Jeremy M Wolfe

After viewing thousands of images presented for a few seconds apiece, an observer can
successfully distinguish old images from new ones (Standing, 1973). How is this
accomplished? Do observers remember a list of objects? Do they remember the
background (e.g. a beach)? In a variation of the standard picture memory experiment, we
created photorealistic scenes of natural settings, urban places and indoors spaces. These
consisted of a background and three added objects consistent with that background.
Subjects were presented with 60 of these scenes for 3 seconds each, and then
immediately tested for their memory. Test stimuli could have the same background, a
similar background (e.g. a different beach with a similar spatial layout), or a different
background. The 3 objects, too, could be the same or all different. Subjects made two
responses; one about the novelty of the objects, the other about the background. Even
though these stimuli resemble each other more than the usual picture memory stimuli,
overall performance was quite good (objects: 74% correct, d' = 1.37, backgrounds: 68%
correct, d'=1.15). Poor performance was found in very specific situations. Whenever
objects were incorrectly classified, performance on the background task dropped to
chance. Whenever observers reported that an old background was new, they were poor at
distinguishing old from new objects (d' = .41). These results would be consistent with
observers simply forgetting some scenes entirely. However, when observers erroneously
reported that a new background was old, classification of objects remained quite good
(d'=1.02 or 0.85 depending on the type of new background). Clearly, observers can recall
the global background and the local objects in a briefly presented scene. These sources of
information interact asymmetrically. Forgotten objects predict a forgotten background,
but a forgotten background may accompany remembered objects.