Inconsistent handedness and saccade execution benefit face memory without affecting interhemispheric interaction

Individuals who consistently use their dominant hand for most tasks exhibit poorer memory than individuals whose handedness is relatively inconsistent, but consistent-handers' memory can be enhanced by making repetitive saccadic eye movements before attempting retrieval. One account of these effects is that inconsistent handedness and saccade execution are associated with increased interhemispheric interaction, which putatively facilitates retrieval. We tested this account by having participants classify faces as famous or novel. Faces were presented in the left and right visual fields simultaneously (bilaterally) or in one field only (unilaterally). As in prior studies, famous faces were classified more quickly and more accurately given bilateral presentation, but novel faces were not. These bilateral gain effects indicate that interhemispheric interaction specifically facilitates famous-face recognition, and therefore larger gains may reflect greater interhemispheric interaction. However, neither inconsistent handedness nor saccade execution increased the size of bilateral gain. Inconsistent handedness and saccade execution (the latter for consistent-handers only) did increase face-classification accuracy, but the increases were not specific to famous-face recognition, and, in fact, were somewhat stronger for novel-face identification. These results extend the beneficial mnemonic effects of inconsistent handedness and saccade execution to faces, but indicate that these benefits are not caused by increased interhemispheric interaction.