The purpose of the present study was to answer the question whether pain report can be increased and decreased by operant conditioning. We predicted that the conditioned pain effects would remain significant after correction for social desirability and fantasy proneness. Furthermore, we tried to show that the neurophysiologic basis of verbal pain report, defined by pain (event)-related potentials, was affected by the conditioning procedure. Specifically, it was expected that the central recording site N150-P260 pain (event)-related potentials peak-to-peak amplitude would show the largest effect.
There were 4 groups: an up-conditioning group, a down-conditioning group, an at-random conditioning, and no-feedback control group. Healthy patients received 45 calibrated pain stimuli of equal physical intensity and were asked to rate the pain intensity they experienced. Up-conditioning was established by rewarding the subject if pain report increased compared with the previous trial. Down-conditioning of pain report was achieved by rewarding a decrease in the pain score.
Results of the subjective pain reports clearly indicated that both forms of conditioning succeeded. Up-conditioning resulted in the highest pain scores and down-conditioning in the lowest scores with the two control groups in between them. Controlling for level of social desirability and fantasy proneness did not negatively influence these results. The N150-P260 pain (event)-related potentials peak-to-peak central recording site component also showed the predicted effect and reached statistical significance.
We concluded that the subjective report of pain as well as a specific pain-related potentials component can be operantly conditioned.