If you’re happy and you know it… sweat? It may sound odd, but new research published this week in the journal Psychological Science indicates that humans produce chemical compounds called chemosignals in our perspiration that lets other smell when we’re happy.
In the study, senior author Gün Semin, a psychological scientist at Utrecht University in the Netherlands, and colleagues demonstrate analyzed sweat samples and found that substances in sweat can communicate positive emotions, not just negative ones such as fear and disgust.
Sweating for science
Building on previous studies that showed that negative emotions could be detected by others through detectible regularities in the chemical compound of sweat, the authors set out to show that the same chemically-based communicative functions also existed 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,” Semin explained. “This suggests that somebody who is happy will infuse others in their vicinity with happiness. In a way, happiness sweat is somewhat like smiling – it is infectious.”
To probe the link, the researchers recruited 12 Caucasian men who were not on any medication and had no psychological disorders to provide sweat samples. During the study, the participants were not allowed to smoke, drink alcohol, have sex, exercise excessively or eat smelly foods.
The donors traveled to the lab, washed and dried their armpits, had an absorbent pad attached to each one and then put on a pre-washed T-shirt. Next, they completed a series of tasks, including viewing a video clip designed to induce a specific emotional state such as fear or happiness, and completed a measure of implicit emotion by ranking the pleasantness of Chinese symbols.
Gauging the communicative ability of perspiration
Afterwards, the pads were removed and stored in vials, and the researchers moved on to the second part of the study, which involved 36 Caucasian women with no psychological disorders, respiratory disease, or other illness. Women were chosen for this part of the task, the authors said, because they have a better sense of smell and are more sensitive to emotional signals.
In a double-blind study, which means that neither the scientist nor the participant knew which type of sweat sample was being used, the women were seated in a chair and placed their chins on a chin rest. A vial filled with a sweat sample was then placed in a holder attached to the chin rest, and the women were exposed to three samples (one indicating fear, one indicating happiness and one neutral) with a five-minute break in between each of them.
Analysis of the data showed that the videos did influence the emotional states of the male study participants (they experienced the desired positive or negative emotion), and based on the facial muscle activity of the women and their behavior, it appeared as though the emotions were passed on through the sweat of the men, suggesting a “behavioral synchronization” between the sweat donor and the recipient, according to the authors.
The findings, the researchers noted, seem to indicate that people can communicate both their positive and negative emotional states through distinct chemosignals. “This is another step in our general model on the communicative function of human sweat,” Semin concluded, “and we are continuing to refine it to understand the neurological effects that human sweat has on recipients of these chemical compounds.”