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 letter-matching tasks: physical-identity letter matching (shape task) and nominal-identity letter matching (name task). Each task contained three conditions. In control conditions, no concurrent task was given. In threat 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 lateral stimulus. With letter naming, each trial consisted of three consonants presented horizontally to the left or right visual field. Across conditions, subjects identified more letters correctly in the right visual 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 letter pairs were identified faster than different pairs when they were presented to the right visual field. The concurrent presentation of threatening words resulted in a selective shortening of left visual-field latencies to same pairs. In the name task, the concurrent presentation of threatening words resulted in improved accuracy on left visual field trials. No sex differences in perceptual asymmetries and in emotional priming effects were found. The results demonstrate that threatening stimuli can activate the right hemisphere and alter the laterality patterns for several tasks.