Normal-mirrored letter recognition, same-different judgment and cerebral dominance.

Either normal or mirror images of Kana, Kanji and capital letters were presented tachistoscopically in a left or right visual field, and then normal letters were flashed simultaneously at the fixation point. Subjects were trained to give same (formula: see text) or different (formula: see text) judgments to pairs of stimuli. Reaction time (RT) and percentage of errors (PE) were measured. Generally, normal letters with same judgments revealed a right field advantage, while with different judgments, there were not significant laterality differences. In the case of mirrored letters, each of two judgments showed no lateral asymmetries for each kind of letters excepting a left field advantage for mirrored Kana words with different judgments. PE methods tended to produce a right field advantage more consistently than did RT methods.