  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.
