High avoidance despite low fear of a second-order conditional stimulus.

This study examined avoidance learning using a second-order threat conditioning paradigm. Participants completed fear acquisition wherein a second-order threat cue (preCS+) was paired with a threat cue (CS+) followed by an aversive sound (US); another stimulus was never associated with the US (CS-). During avoidance conditioning, participants could press a button when the preCS + or the CS- was presented, preventing upcoming events. During response prevention and extinction, the avoidance button was removed. Avoidance persistence was then examined in the absence of the actual threat. Results revealed that although the preCS+ and CS- elicited low levels of fear following Pavlovian fear acquisition, during avoidance conditioning, participants showed more avoidance of the preCS+ than the CS-. They also reported the preCS+ as more dangerous than the CS-. Following extinction, participants returned to actively avoid the preCS+ and rated it as more dangerous than the CS-. Finally, the association between avoidance learning and persistence of avoidance was mediated by self-reported threat expectancy during extinction. Our findings suggest avoidance behavior can be triggered by low levels of experienced fear, and this avoidance may play a role in the development and maintenance of threat beliefs.