Differential conditioning to facial emotional expressions: Effects of hemispheric asymmetries and CS identification

Previous studies on aversive learning have suggested a right hemispheric ad vantage for eliciting autonomic reactions to a masked conditioned facial st imulus (CS) depicting anger. The present study investigated the effects of visual field (VF), stimulus awareness, and emotional valence of the CSs on indicators of conditioning (bilateral SCRs, HR) using a differential condit ioning paradigm (N = 41). In Group 1, four different negatively valenced fa cial expressions (CS+) but not four positively valenced CS- were associated with an unconditioned stimulus (US, aversive vocalization, 97 dB, 3 s) dur ing acquisition. Group 2 received a treatment reversal with positive CS+ as sociated with the US. In a repeated measures design, CSs were presented wit h or without awareness during extinction (two weeks interval, order counter balanced). SOAs were adapted for each subject and condition prior to the ex periment so that identification performance was approaching chance level. T he results revealed that both negative and positive facial expressions coul d be aversively conditioned providing evidence for a generalization of lear ning in the valence dimension. During extinction, preattentive negative CS presented to the left VF showed a trend towards greater electrodermal and cardiac reactions. However, no such effect emerged under full awareness of the CSs. These results confirm and further specify the nature of hemispheri c asymmetries in emotional associative learning.