Defensive responses to phobic stimuli.

Physiological recordings were made while nine females who were afraid of spiders (group P) and nine who were not (group N) viewed a random series of spider and neutral slides. Group P's responses to the spider slides included heart rate (HR) acceleration, cephalic vasoconstriction and an increase in palmer skin conductance (SC), a pattern considered to be part of a defensive response (DR). Group N's responses, on the other hand, were indicative of an orienting response (OR), and included HR deceleration, cephalic vasodilation and an increase in palmar SC. The neutral slides elicited little in the way of responses from group N. However, they elicited the cardiovascular and electrodermal components of an OR from group P, presumably because of their contrast with the feared spider slides. Although the DR pattern observed in group P was often accompanied by increased somatic activity, HR acceleration and cephalic vasoconstriction still occurred even when somatic activity did not appear to increase.