UC Riverside

Language research has moved from the left hemisphere (LH) processing all language, to a differential processing across hemispheres. Davidson (1995) suggests the right hemisphere (RH) is specialized for experiencing negative emotions, while the LH is specialized for experiencing positive emotions. However, when readers' perceive emotion, the RH processes emotion regardless of valence. Examining laterality of perception versus experience of emotions has not been thoroughly tested using cognitive paradigms. Experience was examined using positive, negative, and neutral moods induced via pictures from the International Affective Picture Inventory. We predicted a LH advantage for positive or neutral mood induction and a RH advantage when negative mood was induced. Perception of emotions was tested using valence judgments. Predictions were a RH advantage for natural and man-made target words preceded by positive and negative central words and a LH advantage for targets preceded by neutral central words. An overall LH advantage for the semantic decision task was found. The valence of the central word did have an effect on accuracy and reaction time of the subsequent semantic decision words. Although there was no effect of visual field for the negative mood induction condition, there was a trend toward a significant interaction between mood and visual field. A LH advantage was found for accuracy of the semantic decision task for the positive mood induction, which partially supports experimental predictions. This experiment examined the effect of valence on hemispheric asymmetry. Arousal level was controlled for in order to have a non-confounded measure of valence. Given experimental findings, arousal level may be an important variable when examining valence.