Heart rate and self-report changes accompanying different types of relaxing imagery

Two groups of 10 subjects were instructed, following appropriate training, to evoke different types of relaxing imagery for a total of five 30 s trials. For one group the instruction stressed response elements in the image, for the other stimulus elements. A third, control group of 10 were invited to relax by any means they considered appropriate. No specific imagery instructions were given here. Heart rate was recorded throughout and ratings of sleepiness were made by subjects at the end of each trial. Analogue mood scales were completed pre- and post-experimentally. While the self-report measures intimated an increase in feelings of relaxation and sleepiness over the course of the experiment, no group differences were observed. For heart rate, however, group differences were apparent. Overall, heart rate change during trials took the form of cardiac acceleration. However, while the two imagery groups demonstrated more or less sustained acceleration throughout trial periods, the acceleration observed initially in the control group showed a pronounced linear decline with a net deceleration being recorded toward the end of each trial. The imagining of response or stimulus elements did not differentially affect heart rate. These data imply that the process of imagining constitutes a more important influence on heart rate in these circumstances than image type or affective content.