Effects of signalling parameters on human electroshock perception: Informational control versus stimulus error

Abstract

Informational Control theories predict that (a) a signal preceding a noxious, unavoidable stimulus will reduce the perceived intensity of that stimulus, and (b) it is the information provided by the signal that is responsible for this effect. In the present experiment, the first prediction was evaluated by presenting all subjects with a series of shocks under a signalled condition (light signal preceding shock onset), and two types of unsignalled conditions (light and shock simultaneous, and no light The second prediction was tested during the signalled trials by varying the information provided by the light signal: subjects were divided into four groups, and each group received high or low amounts of temporal and contingency signal information. Neither prediction was supported & the results: (a) a signal preceding the shock did not affect the perceived intensity; (b) subjects magnitude estimations of perceived shock intensity also yielded no significant effects of signal information. However, unsignalled shocks which occurred simultaneously with the light were rated significantly higher in intensity than either the signalled shocks or the unsignalled shocks which were not accompanied by a light. This suggests that simultaneous light signal + shock is an inappropriate control for testing hypothesis (a). We speculate on the reasons for this problem.