Fear Conditioning With Film Clip and Electric Shock Unconditioned Stimuli: What Drives Conditioned Electrodermal Responses?

When compared to audio or video stimuli, previous studies have shown that electric shocks produce stronger electrodermal conditioned fear responses. This difference occurs even if the audio or video stimuli are perceived as more intense and aversive by participants. We re-analyzed two datasets that used a combined trauma film/fear conditioning paradigm to test whether this effect was due to trace conditioning or other factors. We found evidence that weaker electrodermal conditioning when the unconditioned stimulus (US) is a film clip is unlikely to be due to trace conditioning, as no prominent delayed unconditioned responses occurred during the film clip after conditioned stimulus offset. We also found that some film clips elicit unique unconditioned responses, which may depend on the specific timing of the most aversive events within each clip. Finally, we found evidence that larger skin conductance responses during the presentation of one of the four trauma film clips used was associated with more frequently reported intrusive memories. This data provides important new information supporting the idea that skin conductance responses during conditioning using electric shock USs might not reflect purely anticipatory fear, at least in the way conceptualized in the literature. This account has potentially critical implications for the interpretation of fear conditioning research using electric shocks.