Differences in visual attention and task interference between males and females reflect differences in brain laterality

Two cognitive tasks (a letter memory task and a spatial memory task) design ed to selectively activate the left or right hemisphere were combined with attentional probe tasks to measure how hemispheric activation affects atten tion to left and right hemifields. The probe task in Experiment 1 required the identification of digits in the left and right hemifield. During the le tter task; male subjects identified more probes from the left hemifield tha n from the right. Their accuracy varied little across the two hemifields du ring the dots task. Experiment 2 tested whether this pattern is due to either spatial attention or interference in character processing. Instead of identifying digits, th e probe task required subjects to respond to a black square that appeared i n the periphery of the screen. For male subjects, the pattern was opposite of that from Experiment 1. During the letter task they responded faster to the probe in the right hemifield than in the left. Their response times wer e equivalent across the two hemifields during the dots task. These results indicate two separate effects of laterality in male subjects. The activation of one hemisphere produced more attention to the contralate ral hemifield in Experiment 2, and the letter memory task interfered with t he processing of other characters in the right Visual held more than those in the left Visual field in Experiment 1. Neither of these effects appeared in female subjects, corroborating earlier claims that female brains are le ss lateralized than male brains. (C) 2000 Elsevier Science Ltd. All rights reserved.