Rapid detection of neutral faces associated with emotional value.

Swift detection of faces with emotional meaning underlies fruitful social relationships. Although previous studies using a visual search paradigm have demonstrated rapid detection of emotional facial expressions, whether it is attributable to emotional/motivational significance remains to be clarified. We examined this issue by excluding the influence of visual factors on the rapid detection of faces with emotional meaning. First, participants were engaged in an associative learning task wherein neutral faces were associated with either monetary rewards, monetary punishments, or zero outcome in order for the neutral faces to acquire positive, negative, and no emotional value, respectively. Then, during the visual search task, the participants detected a target-neutral face associated with high reward or punishment from among newly presented neutral faces. In Experiment 1, neutral faces associated with high reward and punishment values were more rapidly detected than those without monetary outcomes. In Experiment 2, highly rewarded and highly punished neutral faces were more rapidly detected than neutral faces associated with low monetary reward/punishment. Analyses of ratings confirmed that the learned neutral faces acquired emotional value, and the reaction times were negatively related to arousal ratings. These results suggest that the emotional/motivational significance promotes the rapid detection of emotional faces.