How effective are films in inducing positive and negative emotional states? A meta-analysis

Meta-analyses and reviews on emotion research have shown the use of film clips to be one of the most effective methods of mood induction. Nonetheless, the effectiveness of this method when positive, negative and neutral emotional targets are studied under similar experimental conditions is currently unknown. This comprehensive meta-analysis included only studies that implemented neutral, positive and negative mood inductions to evaluate the effectiveness of the film clip method as a mood induction procedure. In addition, several factors related to the films, sample and experimental procedure used, the number of emotional categories, for example, or the number of film clips watched, were included to study their influence on the effectiveness of this mood induction procedure. Forty-five studies were included with 6675 participants and 12 possible moderator variables according to the sample and the research procedure. Our findings suggest that film clips are especially powerful in inducing negative mood states (Hedges' g for valence = -1.49 and for arousal = -1.77) although they are also effective inducers of positive mood states (Hedges' g for valence of = . -1.22 and for arousal = -1.34). Additionally, this meta-analysis reveals that variables, such as the number of emotional categories or the type of stimulus used to measure the baseline, should be considered.