A test of perceptual enhancement with peripherally presented letter pairs

The present study was conducted to determine whether sensitivity to a member of a pair of stimulus letters projecting to the parafovae would be improved by presenting that member at fixation. The effect was examined for the pair member appearing at a constant distance from fixation, which always was flanked to its inner or outer side. Contrary to expectations based upon results reported by Geiger and Lettvin (1986), observed accuracy changes were found to be due to response bias rather than to sensitivity enhancement.