The effects of direct and imaginal stimulation on physiological and self-report measures : a test of the continuity assumption

One of the primary assumptions underlying the "cognitive trend" in behavior therapy and the covert conditioning model of behavior is that imaginal stimuli elicit reactions comparable to those observed with external stimulation. The present study was designed to test the assumption of continuity between external and imaginal stimuli, and to address several procedural questions related to the covert conditioning behavior therapy techniques. Twelve female college undergraduates were exposed to subjectively determined positive, negative, and neutral stimuli in both their real-life (overt) and imaginal (covert) forms. Exposure to each of the stimuli lasted for 90 seconds. Measures of heart rate, skin conductance, and self-reported affective intensity were used to evaluate autonomic and subjective reactivity to each stimulus. Subjects were exposed to the six experimental stimuli in counterbalanced orders to avoid confounds associated with a standardized sequence of stimulus presentations. Additionally, the saliency of the six stimuli was determined to be roughly equivalent by means of image clarity ratings for covert stimulus presentations, and attentional focus ratings for overt stimulus presentations. Results indicated that reactions to real-life and imaginal stimuli were indistinguishable both across and within the three stimulus valence categories on cardiovascular and verbal response measures, and on a measure of absolute change in electrodermal activity