Abstract
Humans can register another person’s fear not only with their eyes and ears, but also with their nose. Previous research has demonstrated that exposure to body odors from fearful individuals elicited implicit fear in others. The odor of fearful individuals appears to have a distinctive signature that can be produced relatively rapidly, driven by a physiological mechanism that has remained unexplored in earlier research. The apocrine sweat glands in the armpit that are responsible for chemosignal production contain receptors for adrenalin. We therefore expected that the release of adrenalin through activation of the rapid stress response system (i.e., the sympathetic-adrenal medullary system) is what drives the release of fear sweat, as opposed to activation of the slower stress response system (i.e., hypothalamus-pituitary-adrenal axis). To test this assumption, sweat was sampled while eight participants prepared for a speech. Participants had higher heart rates and produced more armpit sweat in the fast stress condition, compared to baseline and the slow stress condition. Importantly, exposure to sweat from participants in the fast stress condition induced in receivers (N = 31) a simulacrum of the state of the sender, evidenced by the emergence of a fearful facial expression (facial electromyography) and vigilant behavior (i.e., faster classification of emotional facial expressions).
Highlights
Accumulating evidence has indicated that humans are capable of communicating fear via the sense of smell
The small yet sufficient sender sample (N = 8) means that the results reported for this sample should be interpreted with caution
Compared to both the baseline and fast stress condition, higher heart rate and sweat production was expected in the fast stress condition (i.e., sympathetic-adrenal medullary (SAM) activity), whereas the slow stress condition was expected to be characterized by high levels of cortisol (i.e., HPA activity)
Summary
Accumulating evidence has indicated that humans are capable of communicating fear via the sense of smell. The present research examined whether the activation of the fight/flight response (i.e., SAM activity) following the introduction of a social stressor would lead to the production of a qualitatively different body odor that would induce a simulacrum of the sender’s state in a receiver. To this end, we first introduced senders to a well-validated social stressor, the Trier Social Stress Task (TSST [39]). Since previous research reported facilitated recognition of fearful facial expressions when these expressions (i.e., visual information) were paired together with fearful voices [45], we expected that exposure to fast stress odor would result in enhanced processing of fearful facial expressions, compared to (other) negative affective expressions (disgust), positive affective expressions (happiness), and neutral expressions
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