Humans may be able to communicate positive emotions like happiness through the smell of our sweat, according to new research published in Psychological Science, a journal of the Association for Psychological Science. The research indicates that we produce chemical compounds, or chemosignals, when we experience happiness that are detectable by others who smell our sweat.
While previous research has shown that negative emotions related to fear and disgust are communicated via detectable regularities in the chemical composition of sweat, few studies have examined whether the same communicative function holds for positive emotions.
“Our study shows that being exposed to sweat produced under happiness induces a simulacrum of happiness in receivers, and induces a contagion of the emotional state,” explains psychological scientist Gün Semin of Utrecht University in the Netherlands, senior researcher on the study.
To determine whether this emotional chemosignaling extends to positive emotions, Semin and colleagues examined whether sweat taken from people in a happy state would influence the behavior, perception, and emotional state of people exposed to the sweat.
The researchers recruited 12 Caucasian males to provide the sweat samples for the study. The participants did not smoke or take any medications, and had no diagnosed psychological disorders.
The sweat donors came to the lab, rinsed and dried their armpits, and had absorbent pads attached to each armpit. They donned a prewashed T-shirt and sat down to complete the study tasks. They watched a video clip intended to induce a particular emotional state (fear, happiness, neutral) and they also completed a measure of implicit emotion, in which they were asked to view Chinese symbols and rate how pleasant or unpleasant each one was. The sweat pads were then removed and stored in vials.
For the second part of the study, the researchers recruited 36 Caucasian females, with no psychological disorder, respiratory disease, or other illness. The researchers note that only females were included in this part of the study as women generally have both a better sense of smell and a greater sensitivity to emotional signals than men do. The study was double-blind, such that neither the researcher nor the participant knew which sweat sample the participant would be exposed to at the time of the experiment.
The women were seated in a chair and placed their chins on a chin rest. The vial containing the sweat sample was placed in a holder attached to the chin rest and was opened immediately prior to the target task. The women were exposed to a sweat sample of each type (fear, happiness, neutral), with a 5-minute break in between samples.
Initial data analysis confirmed that the videos did influence the emotional states of the male participants – men who watched the fear video showed predominantly negative emotion afterward and men who watched the happiness video showed predominantly positive emotion.
But were these emotions conveyed to the female participants? Some behavioral results suggest the answer is ‘yes.’
Facial expression data revealed that women who were exposed to “fear sweat” showed greater activity in the medial frontalis muscle, a common feature of fear expressions.
