Real-world vision: Selective perception and task

Visual perception is an inherently selective process. To understand when and why a particular region of a scene is selected, it is imperative to observe and describe the eye movements of individuals as they go about performing specific tasks. In this sense, vision is an active process that integrates scene properties with specific, goal-oriented oculomotor behavior. This study is an investigation of how task influences the visual selection of stimuli from a scene. Four eye tracking experiments were designed and conducted to determine how everyday tasks affect oculomotor behavior. A portable eyetracker was created for the specific purpose of bringing the experiments out of the laboratory and into the real world, where natural behavior is most likely to occur. The experiments provide evidence that the human visual system is not a passive collector of salient environemental stimuli, nor is vision general-purpose. Rather, vision is active and specific, tightly coupled to the requirements of a task and a plan of action. The experiments support the hypothesis that the purpose of selective attention is to maximize task efficiency by fixating relevant objects in the scene. A computational model of visual attention is presented that imposes a high-level constraint on the bottom-up salient properties of a scene for the purpose of locating regions that are likely to correspond to foreground objects rather than background or other salient nonobject stimuli. In addition to improving the correlation to human subject fixation densities over a strictly bottom-up model [Itti et al. 1998; Parkhurst et al. 2002], this model predicts a central fixation tendency when that tendency is warranted, and not as an artificially primed location bias.