Independence of sensitivity on different foveal areas

Evidence suggests that for close retinal areas a correlation in sensitivity exists between the areas. Correlations as a function of distance from fixation and between areas were studied. In Experiment I, both forms were equidistant from fixation and five different distances apart. In Experiment II, both forms fell on an imaginary line through fixation. The forms usually did not fall on equally sensitive areas as in Experiment I. Both experiments showed that accuracy was lower for two- than for one-form displays. Closer forms had the lowest accuracy, suggesting perhaps mutual contour masking. However, in the sense of an intratrial correlation, no significant relationships were found. These two types of independence were discussed in terms of contour masking and varying sensitivity.