Rule-based generalization of threat without similarity.

Threat generalization to novel instances is central to adaptive behavior. Most previous work has investigated threat generalization based on the perceptual similarity between past and novel stimuli. Few studies have explored generalization based on abstract, non-perceptual relations despite their importance for cognitive flexibility. In order to measure such rule-based generalization of threat without perceptual similarity, we developed a novel paradigm that prevents perceptual features from gaining predictive value. Our results demonstrate that participants responded according to the correct abstract rule and used it to successfully generalize their anticipatory behavioral threat responses (expectancy ratings, sudomotor nerve activity, and heart rate responses). Our results further show that participants flexibly adapted their responses to an unsignaled mid-session contingency reversal. We interpret our results in the context of other rule-based generalization tasks and argue that variations of our paradigm make possible a wide range of investigations into the conceptual aspects of threat generalization.