Static and Dynamic Functional Visual Fields

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Abstract
The size of visual field utilized by the human visual system to input information about the outside world was investigated for static and dynamic viewing conditions. In static conditions, subjects detected a target that was presented in a peripheral position while maintaining central fixation. The size depended greatly on the imposed task: a large field to detect a spot of light, a small field to distinguish a target from background noise, and a still smaller field to distinguish a target from background noise while detecting a figure in the central visual field. In the dynamic condition, subjects read sentences or perceived pictures with restricted sizes of visual field and a critical field size was determined which assured normal perceptual behaviour. The size was about 10° visual angle in both cases, which was quite large compared to the saccadic size of the eye movement, implying a need to input the entire pattern for a limited time. Reasons for such short inputting times are discussed.