Can US sensitization account for the electrodermal variant of the Perruchet effect?

During experiments employing Perruchet's (1985) paradigm there are runs of reinforced (CS-US) trials and non-reinforced (CS-noUS) trials. Conditioned responding (CR) is measured, for example, using eyeblink responses (Perruchet, 1985), reaction times (Perruchet, Cleeremans, & Destrebeceqz, 2006), or changes in skin conductance (SCR; McAndrew, Jones, McLaren, & McLaren, 2012), as well as an online measure of expectancy for the unconditioned stimulus (US). A double dissociation between CR and conscious expectancy of the US is typically found, whereby expectancy of the US decreases while the CR increases across runs of successively reinforced trials. A gambler’s fallacy explanation can be offered for the expectancy data, whereas an associative explanation can be used to explain variations in the CR (consistent with the dual processing theory of McLaren, Green, & Mackintosh, 1994). However, skeptics of this effect have proposed nonassociative explanations of the CR data seen in these experiments. They note that every CS-US pairing is confounded by the presence of the US. Therefore, it is possible that US sensitization, the phenomenon whereby repeated US presentations leads to stronger unconditioned responding to the US, could produce the increasing CR pattern with successive reinforcements (Weidemann, Tangen, Lovibond, & Mitchell, 2009). Two experiments are presented investigating whether US sensitization can explain the recently published electrodermal version of the Perruchet effect.