A central performance drop with luminance stimuli requiring spatial integration

This study reports four experiments that analyzed detection performance for luminance contrasts as a function of retinal eccentricity in order to find further support and explanations for the central performance drop (CPD) in the fovea. In the first experiment, 10 participants (16-37 years of age) had to detect a target patch in a stimulus consisting of bright and dark pixels. Luminance differences between target and context areas were achieved by placing a different number of bright (and dark) pixels in the target and the context area. Results showed a marked CPD; that is, performance did not peak in the fovea but in the parafovea. A spatial integration hypothesis was proposed to explain this CPD. Alternative explanations were tested in three further experiments with a total of 28 participants from 19-46 years of age (using the decision criterion effect, the selective masking effect, and inhibition by high frequencies). The findings did not contradict the spatial-integration hypothesis.