Abstract
When sampling eye-fixations from observers that view natural scenes freely, a consistent pattern emerges where fixation density is highest near the center and decreases away from it. Typically, this center-bias is modeled as a normal spatial distribution of eye-fixations across complete scanpaths, and indeed, such a model was shown successful in facilitating better computational prediction of fixations. However, this view of the center-bias offers little information about any spatio-temporal effects that the center-bias may have during viewing. In the present work, we examine issues like that by analyzing saccades rather than fixations. Moreover, we also focus on a different representation of saccades where saccade orientation and amplitude are separated, examining how they vary as a function of spatial origin and their time/order during the scanpath. The results show that the center-bias is manifested throughout the duration of viewing in both orientation and amplitude. Based on these observations, we propose a more elaborate model of the center bias, which can be used to estimate where observers tend to fixate next. Finally, we show that the proposed model explains the distribution of eye-fixations better than previously suggested models.