Recent years have seen a resurgent interest in eye movements during natural scene viewing. Aspects of eye movements that are driven by low-level image properties are of particular interest due to their applicability to biologically motivated artificial vision and surveillance systems. In this paper, we report an experiment in which we recorded observers’ eye movements while they viewed calibrated greyscale images of natural scenes. Immediately after viewing each image, observers were shown a test patch and asked to indicate if they thought it was part of the image they had just seen. The test patch was either randomly selected from a different image from the same database or, unbeknownst to the observer, selected from either the first or last location fixated on the image just viewed. We find that several low-level image properties differed significantly relative to the observers’ ability to successfully designate each patch. We also find that the differences between patch statistics for first and last fixations are small compared to the differences between hit and miss responses. The goal of the paper was to, in a non-cognitive natural setting, measure the image properties that facilitate visual memory, additionally observing the role that temporal location (first or last fixation) of the test patch played. We propose that a memorability map of a complex natural scene may be constructed to represent the low-level memorability of local regions in a similar fashion to the familiar saliency map, which records bottom-up fixation attractors.
Spatial contrast sensitivity varies considerably across the field of view, being highest at the fovea and dropping towards the periphery, in accordance with the changing density, type, and interconnection of retinal cells. This observation has enabled researchers to propose the use of multiple levels of detail for visual displays, attracting the name image foveation. These methods offer improved performance when transmitting images across low-bandwidth media by conveying only highly visually salient data in high resolution, or by conveying more visually salient data first and gradually augmenting with the periphery. For stereoscopic displays, the image foveation technique may be extended to exploit the additional acuity constraint of the human visual system caused by the focal system: limited depth of field. Images may be encoded at multiple resolutions laterally taking advantage of the space-variant nature of the retina (image foveation), and additionally contain blur simulating the limited depth of field phenomenon. Since optical blur has a smoothing effect, areas of the image inside the high-resolution fovea, but outside the depth of field may be compressed more effectively. The artificial simulation of depth of field is also believed to alleviate symptoms of virtual simulator sickness resulting from accommodation-convergence separation, and reduce diplopia.