Foveal-to-peripheral priming in letter identification reflects response bias, not enhanced visibility.

Several studies have suggested that it might be easier to identify a letter when its replication is simultaneously presented in the visual display. We have measured identification accuracy for a memorized target letter that was shown in the peripheral field in two conditions in which a letter either identical or different in shape was flashed simultaneously at fixation. The results of three forced-choice experiments showed that, contrary to Geiger and Lettvin's (1986) previous findings, an identity prime did not improve the visibility of a temporally backward masked target letter. However, the foveal prime letter could apparently bias the subject's decision so that he/she was much more ready to report the more visible prime letter as the peripheral target.