Autonomic nervous system changes associated with a spider phobic reaction.

Autonomic nervous system arousal should theoretically increase during a phobic reaction. Eleven spider phobics and 11 nonspider phobics viewed spider, seascape, and surgical slides while several physiological responses were continuously recorded. Results indicated that spider phobics showed significantly faster heart rate, greater heart rate variability, and vasoconstriction during spider slide presentations as compared to nonspider phobics. Spider phobics also showed more frequent phasic skin responses but not larger skin response amplitudes to spider slides. Respiration rate and respiration amplitude were not significantly different for the two groups. It appears that while a general autonomic nervous system arousal occurs during a spider phobic reaction, the demand characteristics of the phobic situation may greatly influence which physiological responses are most affected.