[Effects of the unilateral cerebral activation by nonverbal loading on stimulus detection in each visual field...

The relation between the activation level of hemisphere and the laterality of visual detection was investigated under nonverbal loading conditions. In Exp. I, 10 (6 male and 4 female) right handed college students made "same-different" judgements for pairs of random forms (4th, 8th, and 12th polygons) serially presented. In Exp. II, another 10 (5 male and 5 female) subjects responded to similar with different association values. The main findings were as follows: (a) A test stimulus (8th polygon) was recognized more accurately in the left visual field, but this was due to the poor performance in the right visual field, (b) the factor of association value did not influence the visual field superiority, and (c) the task difficulty may be sole factor responsive to the visual field superiority. These results suggested that the visual laterality effects occurred only when the level of hemispheric loading was optimal.