Context-dependent effects of steroid chemosignals on human physiology and mood

We examined the physiological and psychological effects of nanomolar amount s of steroids applied directly under the nose (Delta4,16-androstadien-3-one and 1,3.,5,(10),16-estratetracn-3-ol). These potential human chemosignals were not consciously discernible in a strong-odor carrier (clove oil and pr opylene glycol). In a double-blind, within-subject, repeated-measures exper iment with 65 subjects, we demonstrated that both steroids produced sustain ed changes in digit skin temperature and palmar skin conductance (an indica tor of sympathetic nervous system tone) while the subjects were completing psychological questionnaires or reading. These effects, however, did not fo llow the sex-stereotyped pattern predicted by a sex attractant function. Bo th androstadienone and estratetraenol raised the skin temperature of men's hands and lowered it in women. Likewise, each steroid increased skin conduc tance, with a significantly greater effect on women than men. Women's respo nses were observed only in the sessions run by the male tester, an effect t hat may or may not be solely attributable to tester sex. Men's responses, i n contrast, were not affected by this difference in socioexperimental condi tion. Similarly, women experienced an immediate increase in positive mood o nly in the presence of the male tester, while men's responses were unaffect ed by this socioexperimental context. One source of this sex difference may be the fact that the majority of women were in the late follicular phase o f their menstrual cycle. Although it is premature to classify these steroid s as pheromones, our data suggest that they function as chemosignals that m odulate autonomic nervous system tone as well as psychological state. (C) 2 001 Elsevier Science Inc. All rights reserved.