Effects of the expression of pain on autonomic and pain tolerance responses to subject-controlled pain.

A within-subjects experiment was performed to investigate the effect of various levels of pain expression on autonomic and tolerance responses to electrical shocks which were terminated by the subjects at their tolerance level. Ten male undergraduates posed three levels of pain expression while being shocked by a constant current source that was turned up rapidly, slowly, or not at all. It was found that skin conductance responses to shock are monotonically and positively related to the level of expression; skin conductance is not significantly affected by expression in the absence of shock; pain tolerance levels are not related to the level of expression; and tolerance levels are higher for rapidly ascending shock than for slowly ascending shock. The implications of these results for theories of the expression of emotion are discussed.