One plus one is more than two: The interactive influence of group membership and emotional facial expressions on the modulation of the affective startle reflex.

It has been demonstrated repeatedly that the evaluation of a face is not only influenced by the social message that is signaled by the face's emotional expression, but also by other social factors such as ethnicity or group membership. Studies in the field of startle research, however, have hitherto investigated only the effects of one of the two factors - that is, either emotional expression or group membership - on the startle response. Yet, we propose that the startle reflex is a sensitive marker for the interactive effect of both factors. Specifically, we predicted that group membership influences the social meaning signaled by an emotional expression, leading to an interactive effect. In two experiments, we examined the modulation of the startle response by happy, fearful, and angry expressions shown by ingroup and outgroup members. As predicted, an interaction between group membership and emotional expression emerged, such that happiness expressed by an ingroup member resulted in lower startle responses compared to the same expression shown by an outgroup member; the opposite pattern emerged for fearful and angry expressions. This effect was found in both experiments and independent of the exact stimulus materials employed, pointing to the generalizability of the effect.