Prediction Errors Drive UCS Revaluation and not Classical Conditioning: Evidence and Neurophysiological Consequences

Nowadays, the experimental study of emotional learning is commonly based on classical conditioning paradigms and models, which have been thoroughly investigated in the last century. On the contrary, limited attention has been paid to the revaluation of an unconditioned stimulus (UCS), which, as experimentally observed by various researchers in the last four decades, occurs out of classical conditioning. For this reason, no analytical or quantitative theory has been developed for this phenomenon and its dynamics. Unluckily, models based on classical conditioning are unable to explain or predict important psychophysiological phenomena, such as the failure of the extinction of emotional responses in certain circumstances. In this manuscript an analytical representation of UCS revaluation learning is developed; this allows us to identify the conditions determining the “inextinguishability” (or resistant-to-extinction) property of emotional responses and reactions (such as those observed in evaluative conditioning, in the nonreinforcement presentation of a conditioned inhibitor, in post-traumatic stress disorders and in panic attacks). Furthermore, an analysis of the causal relation existing between classical conditioning and UCS revaluation is provided. Starting from this result, a theory of implicit emotional learning and a novel interpretation of classical conditioning are derived. Moreover, we discuss how the proposed theory can lead to the development of new methodologies for the detection and the treatment of undesired or pathological emotional responses, and can inspire animal models for resistant-to-extinction responses and reactions.