Abstract: | This study tested twelve hypotheses derived from psychophysiological theory underlying the systematic desensitization method of reducing phobic anxiety. Subjects with phobias imagined threatening scenes and neutral scenes under relaxed or non-relaxed conditions while cardiac, respiratory, digital vasomotor, and skin conductance activity was recorded. Seven hypotheses were confirmed for one or more response measures. The results indicated that (a) imagining threatening scenes produces autonomic arousal in direct proportion to degree of subjective threat associated with the scenes, (b) autonomic reactions do not extinguish and countercondition faster to weak stimuli than to strong stimuli, and (c) muscle relaxation has a demonstrable but limited effect on counteracting autonomic fear reactions. Desensitization theory was partially supported. |