Abstract
Considerable evidence suggests that the encoding of visual input into memory is strongly affected by attention. For example, encoding of a scene is reduced if spatial attention is drawn away by a demanding rapid-serial-visual-presentation (RSVP) task at fixation. However, encoding under such conditions of divided attention is improved if a scene is particularly salient or novel. Here, we show that the encoding of a scene is also enhanced at behaviorally relevant points in time, regardless of the content of the scene and the focus of spatial attention.
In Experiment 1, after being familiarized with a set of scenes, participants were presented with 16 scenes in a RSVP and were surprisingly unable to recognize whether a specific test scene had appeared in the previous sequence of scenes. In Experiment 2, the same set of scenes was presented, but attention was directed to a demanding task at fixation where the goal was to identify a white target letter among a stream of black distractor letters. As before, one scene was presented for a recognition test immediately after each sequence. Surprisingly, recognition performance was at chance except when the test scenes had been presented concurrently with the white target letters. When interviewed, subjects were unaware of their enhanced memories for these target-concurrent scenes. In Experiment 3, enhanced encoding of visual scenes was also found at the specific time of an auditory target.
Results suggest that at behaviorally relevant points in time, visual traces of the visual field are automatically encoded into memory regardless of the spatial focus of attention. It is as though the visual system is performing a ‘screen capture’ at the time of target identification; such a screen capture mechanism may play an important role in the retrospective analysis of important events.
National Institute of Health (NIH) EY 12925 to GMB.