Cerebral Dominance, Language, and Emotion: A Divided Visual Field Study of Lateral Asymmetries in the Processing of Verbal Stimuli.

Abstract

Thirty male and thirty female undergraduate students participated in a divided visual field study designed to examine the effects of emotional content on cerebral lateral asymmetries in the processing of verbal stimuli. The study utilized a randomized block design with a three-factor factorial arrangement of treatments. Each of the three within-subjects factors has two levels, resulting in a Task (lexical, affect-salient) x Word Type (happy, sad) x Visual Field (left, right) design. A bilateral presentation/manual response paradigm was utilized. In the lexical task, emotional words were paired with nonsense words and subjects were asked to respond to the "real English word". In the affect-salient task, happy and sad words were paired with neutral words and subjects were asked to response to the "emotional word". Both accuracy and response time data were measured and reported. Based on current theoretical models of cerebral organization and emotion, it was proposed that attention to the effective content of words would effect cerebral processing, resulting in a left visual field/right hemisphere advantage for sad words and a right visual field/left hemisphere advantage for happy words. A significant main effect for visual field and significant three-way task x word type x visual field interaction was predicted. Analysis of variance with repeated measures found a significant effect of visual field, with a RVF/LH advantage in both accuracy and speed of processing words. The task x word type x visual field interaction was significant for response speed only, and the results were opposite to those predicted. A word type x visual field effect was found in the lexical task but not the affect-salient task. Between-subjects variability was significant and individual laterality indices were calculated on the accuracy data for each subject on each task. The results were discussed in terms of the proposed theoretical models and methodological concerns of divided visual field studies.