EFFECTS OF PROCESSING REQUIREMENTS ON HEMISPHERIC ASYMMETRIES FOR NUMBER JUDGMENTS

Both functional and neuroanatomical aspects of number processing were examined in three experiments. College students judged single Arabic d igits with respect to numerical (odd/even), verbal (phonemic), or visu o-perceptual (horizontal symmetry) features. Care was taken to control for confounding factors by (1) requiring a manual response, (2) verti cally aligning the response keys, (3) using catch trials, and (4) coun terbalancing for combination of hand and judgment category, permitting a modified hand-by-visual field analysis. Although no evidence of hem ispheric asymmetries emerged under any of the different processing req uirements, equal hemispheric efficiency was confirmed only for the jud gment of visuoperceptual features.