The idea that distinct psychosocial factors may underlie specific patterns of neuroendocrine stress responses has been a topic of recurrent debate. We examined a recent contribution to this debate, the Social Self Preservation Theory, which predicts that stressors involving social evaluative threat (SET) characteristically activate the hypothalamic-pituitary-adrenal (HPA) axis.
Sixty-one healthy university students (31 females) performed a challenging speech task in one of three conditions that aimed to impose increasing levels of SET: performing the task alone (no social evaluation), with 1 evaluating observer, or with 4 evaluating observers. Indices of sympathetic (pre-ejection period) and parasympathetic (heart rate variability) cardiac drive were obtained by impedance- and electrocardiography. Salivary cortisol was used to index HPA activity. Questionnaires assessed affective responses.
Affective responses (shame/embarrassment, anxiety, negative affect, and self-esteem), cortisol, heart rate, sympathetic, and parasympathetic activation all differentiated evaluative from non-evaluative task conditions (p<.001). The largest effect-sizes were observed for cardiac autonomic responses. Physiological reactivity increased in parallel with increasing audience size (p<.001). A rise in cortisol was predicted by sympathetic activation during the task (p<.001), but not by affective responses.
It would appear that SET determines the magnitude, rather than the pattern, of physiological activation. This potential to broadly perturb multiple physiological systems may help explain why social stress has been associated with a range of health outcomes. We propose a threshold-activation model as a physiological explanation for why engaging stressors, such as those involving social evaluation or uncontrollability, may appear to selectively induce cortisol release.