Retinal eccentricity and the detection of targets.

It is known that the detectability of a target depends on its similarity to the individual context elements. This article attempts to show that global properties of the context can also influence detection performance. For example, the detection of an O among several Hs appears to be easier than the detection of an H among several Os, because the context consists of elements that are more angular. However, this angular-context advantage is most apparent when the stimulus projection falls on extrafoveal areas of the retina. The results of two stimulus manipulations suggest that the decreasing ability of the visual system with increasing eccentricity could be responsible for this relationship. Increasing the distance between the single elements, and thus reducing the effect of lateral inhibition, led to a deterioration in performance; and by defocusing the stimulus presentation it was possible to achieve an improvement in performance.