Threat determines affective startle potentiation

Affective startle modulation often is attributed to the valence dimension of applied foreground stimuli, whereas alternative views refer to specific discrete emotions. Based on the idea of the startle reflex being a protective mechanism, the significance of threat to the acoustic startle response was tested. Affectively charged pictures were selected according to their quantified discrete-emotional distinctness: pictures primarily evoking sadness, anger, and disgust (low valence); pictures primarily evoking fear (threat; moderately low valence); and pictures primarily evoking happiness (high valence). Electromyography (EMG) of the orbicularis oculi muscle revealed substantial startle potentiation by the fear evoking stimuli. Moreover, evidence was found that disgust bears a strong relation to the startle reflex. In line with other recent studies the reported findings suggest that startle is being increased by threat to one's physical integrity, as is signaled by the discrete emotions of fear and disgust.