Visual lobe area for single targets on a competing homogeneous background

The binocular visual lobe for a detection task, with a peripherally presented target embedded in a homogeneous competing background, was mapped on eight axes passing through the fixation point. The lobes were very irregular in shape and there were differences between the subjects. The eight-axis area correlated highly with area based on only the horizontal and vertical axes, but the latter area gave no indication of even gross irregularities in lobe shape. Lobe areas for two subjects were exhaustively mapped; resulting boundaries were very irregular and there were regions of insensitivity within the lobe area. It was suggested that lobe shape as well as area is important to visual search. The irregular boundary and areas of insensitivity may partly account for the difficulty experienced by some subjects in locating targets even after repeated scanning.