Cortical Magnification Neutralizes the Eccentricity Effect in Visual Search

We report two visual search experiments that explain an eccentricity effect previously found: detection of both feature and conjunction targets becomes increasingly less efficient as the orientation target appears at more distant field eccentricities (Carrasco et al., 1995). By cortically magnifying the stimuli we flattened out this effect for both feature and conjunction tasks. We conclude that spatial resolution factors affect visual search findings that have hitherto been attributed to covert attention. We stress the importance of analyzing data by target position to minimize the confound of the set size effect and retinal/field eccentricity. An alternative theory of orientation asymmetries is offered.