Reappraisal of threat value: loss of blocking in human aversive conditioning.

Non-specificity of fear is a core aspect of what makes anxiety disorders so impairing: Fear does not remain specific to a single stimulus paired with danger, but generalizes to a broad set of stimuli, resulting in a snowballing of threat signals. The blocking procedure can provide a valuable laboratory model for gaining insight into such threat appraisal and generalization processes. We report two experiments in which we induced selective threat appraisal by using a blocking procedure in human aversive conditioning. We subsequently assessed to what extent such selective threat appraisal is sensitive to different kinds of interference. Results illustrate that the maintenance of selective threat appraisal is not guaranteed: Stimuli present during an aversive conditioning event that are initially tagged with a low threat value, can come to be tagged with a higher threat value later on, without additional experience with these stimuli. We argue that such interference in selective threat appraisal might be one of the mechanisms underlying the pathogenesis of non-specific fear.