Tunnel Vision Induced by a Foveal Load Manipulation

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Abstract
In a tachistoscopic dual-task study, the foveal load of a primary task was varied, and subjects were required to report the orientation of a simultaneously presented peripheral line that could occur at anyone of six retinal locations (3, 6, or 9 deg from central fixation in either the left or right visual field). Overall peripheral (secondary) task accuracy was significantly superior for subjects given a low foveal load that required naming a letter drawn from a set of two alternatives as compared with the accuracy of subjects who had to choose a foveal response from among six alternatives. Foveal load interacted strongly with retinal eccentricity. Accuracy of peripheral line-orientation discrimination deteriorated much more rapidly with increases in retinal eccentricity for the high-foveal-load group than for the lowfoveal-load group. These results are discussed in terms of a tunnel-vision model.