Behavior control over aversive events: does control that requires effort reduce anxiety and physiological arousal?

Although it has been suggested that the ability to control (avoid) an aversive event will reduce arousal, it may be that the effort associated with exercising the control will offset the arousal reduction associated with avoidance. To determine whether the amount of effort required to control an aversive event influenced the amount of anxiety and physiological arousal associated with the aversive event, 89 subjects participated in a 3 (unavoidable threat, avoidable threat, no threat) X 2 (high-effort task performance, low-effort task performance) X 2 (anticipation period, performance period) factorial experiment. The results indicated that (a) the aversive event (threat of electrical shock) increased subjects' anxiety and physiological arousal; (b) exercising control was effective for decreasing subjects' anxiety to the non-threat level but only when low effort was required; (c) the prospect of control decreased subjects' physiological arousal to the no-threat level while the subjects were waiting to exercise control over the aversive event; however, (d) while actually exercising the control, subjects showed high physiological arousal like that of subjects who could not control the event. These findings impose important qualifications on the speculations concerning the influence of control.