Modulation of the acoustic startle reflex by emotionally-toned film-clips

It has been widely reported that the eyeblink component of the acoustic startle reflex can be modulated by emotionally-toned slide stimuli; pleasant slides reduce eyeblink amplitudes whereas unpleasant slides enhance them. The present study examines the modulation of the acoustic startle reflex by short (2-min) film-clips classified as pleasant, unpleasant or neutral, on the basis of subjective ratings. These film-clips were also evaluated with respect to their test-retest reliability in producing affective states as well as modulating startle reflexes. Overall, results showed significant reduction of startle during pleasant clips and augmentation during unpleasant clips. However, on first showing, one of the two unpleasant clips (a medical demonstration film depicting details of toe surgery) actually inhibited the startle reflex rather than augmented it. This is discussed in terms of the proposition that only stimuli which arouse fear can be guaranteed to augment startle; stimuli that are repulsive may produce perceptual and emotional 'blunting' that reduces startle amplitude.