RESUMEN
The key point of a paradigm initially proposed by Perruchet (Pavlov J Biol Sci 20:163-170, 1985) to dissociate conscious expectancies from automatic-link formation in classical conditioning settings is the use of a partial reinforcement schedule, in which the unconditioned stimulus (US) follows the conditioned stimulus (CS) only half of the time on average. Given (pseudo) randomization, the whole sequence comprises runs of CS alone and runs of CS-US pairs of various lengths. When the preceding run goes from a long sequence of CS alone to a long sequence of CS-US pairs (via shorter sequences), associative strength should grow up, whereas conscious expectancy should decrease. Earlier studies have shown that, in most cases, conditioned performance parallels associative strength. As an exception, however, a few reports suggest that conditioned electrodermal responses (EDRs) would follow predicted changes in US expectancies. This paper presents an experiment that replicates this outcome. However, when the performances from a control group were taken as a baseline to control for response habituation, corrected conditioned EDRs were shown to follow associative strength. This suggests that the atypical pattern of conditioned EDRs in the Perruchet paradigm would be due to the fact that EDRs are more sensitive to habituation than responses involved in other associative learning settings. These results further challenge the recent "propositional" view of conditioning, which stipulates that conditioned responses in humans are the consequence of participants' conscious inferences about the relationships between the CS and the US, which would lead the CS to generate conscious expectancy for the US.