Participants viewed a series of standard images from the International Affective Picture System (Lang et al. 2008). Images are categorized as affectively pleasant or aversive or as affectively neutral. Eye blink reactions to loud noise probes during viewing of the images were recorded from the orbicularis oculi muscle, and three measures of reactivity derived. Overall startle is the overall magnitude of the integrated electromyographic response averaged over all the trials; overall startle is moderately heritable in this MTFS sample (Vaidyanathan et al. 2014a) and the acoustic startle response has been reported as deviant in schizophrenia patients (Braff et al. 1992). Aversive difference startle is the z-score difference in mean startle magnitude between aversive and neutral images whereas pleasant difference startle is the difference between the pleasant and neutral images.
