Electrodermal conditioning to stimuli of evolutionary significance: Failure to replicate the preparedness effect

In the present study, an attempt was made to replicate the preparedness effect reported by Öhman, Fredrickson, Hugdahl, & Rimmö (1976). Following Öhman et al. (1976) as closely as possible, a differential conditioning procedure was carried out in which subjects'skin conductance responses (SCRs) were conditioned either to stimuli of evolutionary significance (slides of snakes and spiders) or to evolutionally neutral stimuli (slides of mushrooms and flowers). The experiment consisted of 8 habituation, 12 acquisition, and 20 extinction trials. Electric shock served as an unconditioned stimulus during the acquisition phase. Although SCRs showed significant decreases during habituation and were significantly influenced by the conditioning procedure during acquisition, they were not found to extinguish significantly more slowly in the group that saw slides of snakes and spiders. This result contradicts the earlier results reported by Öman and colleagues. Possible explanations for this failure to replicate their results are discussed.