Abstract
While a single approaching object is known to attract spatial attention, it is unknown how attention is directed when the background looms towards the observer as s/he moves forward in a quasi-stationary environment. In Experiment 1, we used a cued speeded discrimination task to quantify where and how spatial attention is directed towards the target superimposed onto a cloud of moving dots. We found that when the motion was expansive, attention was attracted towards the singular point of the optic flow (the focus of expansion, FOE) in a sustained fashion. The effects were less pronounced when the motion was contractive. The more ecologically valid the motion features became (e.g., temporal expansion of each dot, spatial depth structure implied by distribution of the size of the dots), the stronger the attentional effects. Further, the attentional effects were sustained over 1000 ms. Experiment 2 quantified these attentional effects using a change detection paradigm by zooming into or out of photographs of natural scenes. Spatial attention was attracted in a sustained manner such that change detection was facilitated or delayed depending on the location of the FOE only when the motion was expansive. Our results suggest that focal attention is strongly attracted towards singular points that signal the direction of forward ego-motion.
Highlights
The psychophysics of overt and covert attention is a well explored subject with deep roots [1]
When the size of the dots changed over time, they did not signal the location of the singular point but they assisted the ecological interpretation of the motion and depth structure of the dots
In this paper, we explored the attentional effects of the singular point defined by motion, object expansion and 3D depth structure
Summary
The psychophysics of overt and covert attention is a well explored subject with deep roots [1]. The physiological correlates of visual attention are beginning to be understood at both the single neuron [2,3] and at the brain regional level [4]. This has given rise to detailed computational models of the factors that control the allocation of bottom-up, saliency-driven attention in both artificial and natural static scenes [5,6,7]. Looming stimuli signify biological urgencies or dangers, especially when they approach closer to the body, implying a potential interaction between motion, the projected size of an object on the retina, and attention. To fully understand how attention works in a realistic situation, it is necessary to study how the retinal optic flow that accompanies looming stimuli, ego motion and 3D scene structures affect and guide attentional mechanisms
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