Additional support for the existence of skin conductance responses at unconditioned stimulus omission.

The existence of a skin conductance response to an expected but omitted aversive stimulus has recently been challenged. To counter this claim, we provide a review of the literature and a temporal analysis of two independent skin conductance data sets during aversive conditioning and extinction that demonstrates a consistent and reproducible skin conductance response at omission of an anticipated aversive stimulus. The validity of this so-called unconditioned stimulus (US) omission response is relevant for skin conductance modeling in the context of neuroimaging and more generally for conditioning theory.