Revisiting the learning-without-awareness question in human Pavlovian autonomic conditioning: focus on extinction in a dichotic listening paradigm.

Numerous studies have indicated that, consistent with current "cognitive" accounts of information processing, human Pavlovian autonomic discrimination acquisition cannot occur without awareness of the CS-US relationship. However, extinction studies have suggested that awareness is not necessary, findings that, in information-processing terms, have been explained by assuming that the processing by the extinction stage is parallel (automatic) rather than serial (controlled). This explanation was tested in an 80-subject study. The first, acquisition phase was a standard semantic differential conditioning arrangement with a 96-db white noise as US, and a "long" CS-US interval of 8 s, with ten trials each of CS+ (paired with US) and CS- (unpaired) trials. In extinction (USs omitted), in order to obtain non-autonomic indices of processing and thereby test the information-processing account of "unaware" autonomic conditioning during extinction, a dichotic listening task was implemented, with the CSs presented in the unattended channel (ear), while the subject had to perform a semantic differential reaction task in an attended-to channel (other ear). In early extinction, the electrodermal response occurring at an interval of 9-15 s after CS onset (i.e., following placement of the US during acquisition) and the finger-pulse-volume response occurring at an interval of 4-11 s after CS onset both showed reliable conditioning, but reaction-time and subjective-report data for the recognized critical words indicated serial rather than parallel processing of the CSs during extinction.