Threat-Relevant Stimuli Enhance Autonomic Arousal Without Widening Generalization

Inherently threatening stimuli have consistently been shown to resist extinction. Despite recent findings suggesting that defensive responses can generalize to safe but threat-relevant stimuli, it is unclear whether threat relevance can cause overgeneralization. To this end, we investigated two groups of participants who underwent a differential conditioning paradigm with either two angry (threat relevance, n = 38) or two neutral male faces (control, n = 39) as conditioned stimuli (CSs). One of the faces (CS+) was reinforced with a 90-dB scream (unconditioned stimulus, US) 80% of the time, while the other face (CS-) was never followed by the US. In the generalization test, the CSs were presented along with four generalized stimuli that lay on a continuum between CS+ and CS-. Successful acquisition was registered for all ratings and psychophysiological responses except ssVEPs. The differential skin conductance responses (SCRs) were larger in the threat relevance group compared to the control group. During the generalization test, adaptive generalized responses were observed for all measures, except for ssVEPs. Participants’ SCRs to all stimuli were on average larger in the threat relevance group. The shape of the generalization gradients did not differ between the groups suggesting that while threat relevance influences the intensity of autonomic arousal both in acquisition and in generalization, it does not lead to overgeneralization.