Human gender differences in the perception of conspecific alarm chemosensory cues

Abstract

It has previously been established that, in threatening situations, animals use alarm pheromones to communicate danger. There is emerging evidence of analogous chemosensory “stress” cues in humans. For this study, we collected alarm and exercise sweat from “donors,” extracted it, pooled it and presented it to 16 unrelated “detector” subjects undergoing fMRI. The fMRI protocol consisted of four stimulus runs, with each combination of stimulus condition and donor gender represented four times. Because olfactory stimuli do not follow the canonical hemodynamic response, we used a model-free approach. We performed minimal preprocessing and worked directly with block-average time series and step-function estimates. We found that, while male stress sweat produced a comparably strong emotional response in both detector genders, female stress sweat produced a markedly stronger arousal in female than in male detectors. Our statistical tests pinpointed this gender-specificity to the right amygdala (strongest in the superficial nuclei). When comparing the olfactory bulb responses to the corresponding stimuli, we found no significant differences between male and female detectors. These imaging results complement existing behavioral evidence, by identifying whether gender differences in response to alarm chemosignals are initiated at the perceptual versus emotional level. Since we found no significant differences in the olfactory bulb (primary processing site for chemosensory signals in mammals), we infer that the specificity in responding to female fear is likely based on processing meaning, rather than strength, of chemosensory cues from each gender.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

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Summary of the Study by SinglePheromones.com:

In this study, sweat samples were collected from stressed individuals (parachute jumpers) as well as from individuals in non-stressful situations (running on a treadmill), which were then inhaled by the participants. It was found that individuals inhaling sweat from stressed jumpers themselves became stressed. This was not observed in individuals inhaling sweat from those exercising on the treadmill. It turns out that our sweat informs others about our current emotional state. Humans, like animals, use alarm pheromones to convey information about threats.