Accurate visual memory for previously attended objects in natural scenes.

The nature of the information retained from previously fixated (and hence attended) objects in natural scenes was investigated. In a saccade-contingent change paradigm, participants successfully detected type and token changes (Experiment 1) or token and rotation changes (Experiment 2) to a target object when the object had been previously attended but was no longer within the focus of attention when the change occurred. In addition, participants demonstrated accurate type-, token-, and orientationdiscrimination performance on subsequent long-term memory tests (Experiments 1 and 2) and during online perceptual processing of a scene (Experiment 3). These data suggest that relatively detailed visual information is retained in memory from previously attended objects in natural scenes. A model of scene perception and long-term memory is proposed. Because of the size and complexity of the visual environments humans tend to inhabit, and because high-acuity vision is limited to a relatively small area of the visual field, detailed perceptual processing of a natural scene depends on the selection of local scene regions by movements of the eyes (for reviews, see Henderson & Hollingworth, 1998, 1999a). During scene viewing, the eyes are reoriented approximately three times each second by saccadic eye movements to bring the projection of a local scene region (typically a discrete object) onto the area of the retina producing the highest acuity vision (the fovea). The periods between saccades, when the eyes are relatively stationary and detailed visual information is encoded, are termed fixations and last an average of approximately 300 ms during scene viewing. During each brief saccadic eye movement, however, visual encoding is suppressed (Matin, 1974). Thus, the visual system is provided with what amounts to a series of snapshots (corresponding to fixations), which may vary dramatically in their visual content over a complex scene, punctuated by brief periods of blindness (corresponding to saccades).