Selective Visual Attention: Computational Models and Applications

6.3 Eye-tracking Data

The third type of ground-truth data, which can be used in evaluating visual attention models, is the eye-tracking data [5, 16]. An eye-tracker is a device for automatically measuring subjects' eye positions, movements and the associated durations. Thus, tracking of the eye fixations of observers to the images provides the ground-truth to evaluate the performance of visual attention models. This is achieved by comparing the yielded saliency map with the human eye fixation map generated by eye-tracking. The use of eye-tracking overcomes the drawback of human-labelling mentioned in Section 6.2.

One database of human eye fixation is given in [5], which includes 120 images and their human eye fixation data obtained from 20 subjects. The human eye fixation database in [5] has been acquired as follows. Images are presented to a subject in a random order for several seconds. Subjects were positioned 0.75 m from a 21-inch CRT monitor and given no particular instructions. The eye-tracking apparatus used was a standard non-head-mounted device, and the subjects looked at the images in a natural manner. The eye-tracker recorded the fixation points from subjects for the images. In this database, a raw fixation map is produced for each image, based on all the fixation points and subjects.

Post-processing can be performed to derive a continuous fixation density map from the raw fixation map. As we know, when a subject looks at an image, the image is projected onto the retina ...