Reversing threat contingencies enhances generalization of conditioned fear

Generalization of conditioned fear to stimuli resembling a conditioned danger-cue (CS+) is proposed as a key mechanism of clinical anxiety. Given that threat contingencies can be ever changing in day-to-day life, the impact of such changes on generalization is critical to under-standing how generalization manifests in the lives of those with and without clinical anxiety. Here, we add a reversal of threat contingency manipulation to a well validated fear-generalization paradigm to provide the first assessment of reversal effects on generalized conditioned fear. Healthy adult participants were presented rings of increasing size, with extreme sizes serving as CS+ (paired with electric shock) and CS-(never paired), and intermediate sizes serving as generalization stimuli (GS) that formed a continuum-of-similarity between CS+ and CS-. An acquisition phase including CS+ and CS-presentations was followed by a generalization test including presentations of each ring sizes (CS+, GSs, CS-). One group of participants (n = 26) received a CS+/CS-reversal instruction prior to generalization, while a second group (n = 29) received no such instruction. Though comparable levels of discriminative conditioning to CS+ versus CS-were found across groups, the reversal group displayed greater generalization of both perceived threat and fear-potentiated startle relative to the no reversal group. Such results indicate a generalization-enhancing effect of reversing threat contingencies and highlight the importance of future work studying the clinical relevance of this effect.