Standardized mood induction with happy and sad facial expressions.

The feasibility of applying ecologically valid and socially relevant emotional stimuli in a standardized fashion to obtain reliable mood changes in healthy subjects was examined. The stimuli consisted of happy and sad facial expressions varying in intensity. Two mood-induction procedures (happy and sad, each consisting of 40 slides) were administered to 24 young healthy subjects, who were instructed to look at each slide (self-paced) and try to feel the happy or sad mood expressed by the person in the picture. On an emotional self-rating scale, subjects rated themselves as relatively happier during the happy mood-induction condition and as relatively sadder during the sad mood-induction condition. Conversely, they reported that they were less happy during the sad mood-induction condition and less sad during the happy mood-induction condition. The effects were generalized to positive and negative affect as measured by the Positive and Negative Affect Scale. The intraindividual variability in the effect was very small. In a retest study after 1 month, the mood-induction effects showed good stability over time. The results encourage the use of this mood-induction procedure as a neurobehavioral probe in physiologic neuroimaging studies for investigating the neural substrates of emotional experience.