ALTERED VISUAL-FIELD ASYMMETRIES FOR LETTER NAMING AND LETTER MATCHING AS A RESULT OF CONCURRENT PRESENTATION OF THREATENING AND NONTHREATENING WORDS

Thirty-two right-handed subjects (16 male and 16 female students) were administered a unilateral letter-naming task and two unilateral lette r-matching tasks: physical-identity letter matching (shape task) and n ominal-identity letter matching (name task). Each task contained three conditions. In control conditions, no concurrent task was given. In t hreat and nonthreat conditions, each unilateral stimulus was preceded by a centrally presented threatening or nonthreatening word. Subjects were instructed to recall this word after their response to the latera l stimulus. With letter naming, each trial consisted of three consonan ts presented horizontally to the left or right visual field. Across co nditions, subjects identified more letters correctly in the right visu al field than in the left visual field. The concurrent presentation of threatening words resulted in a selective enhancement of left visual- field performance. In the control condition of the shape task, same le tter pairs were identified faster than different pairs when they were presented to the right visual held. The concurrent presentation of thr eatening words resulted in a selective shortening of left visual-held latencies to same pairs. In the name task, the concurrent presentation of threatening words resulted in improved accuracy on left visual fie ld trials. No sex differences in perceptual asymmetries and in emotion al priming effects were found. The results demonstrate that threatenin g stimuli can activate the right hemisphere and alter the laterality p atterns for several tasks. (C) 1995 Academic Press, Inc.