BOSTON — Human social interactions are shaped by more than just words and gestures. Factors such as smell and proximity, and even temperature, all influence how people relate to one another and can affect their behavior.
And scientists are learning more about how this less obvious factors shape our relationships.
Recently discovered evidence for these hidden signals was presented here last week at the Association for Psychological Science Convention.
Our environmental surroundings appear to affect our judgments of both people and things, said Gün R. Semin, a researcher at Utrecht University in The Netherlands. In one experiment, subjects were asked to read narratives of people acting intelligently, neutrally or stupidly, and asked to rate characteristics about that person, such as their intelligence and sociability.
When the room was warmer, participants rated the character as more sociable compared with when it was colder. They also judged the experimenter in charge of instructing the task as more sociable when the heat was on.
The work seems in line with some previous studies that have found a link between temperature and our social feelings. For instance, a 2008 studied showed that people who recall memories of isolation judge a room to be colder than those who recall more happy social experiences of being accepted.
Semin performed the same experiment again, but this time looked at the effects of distance between people on their judgments. When subjects were sitting next to each other (each at a computer), they rated the individuals in the narratives as being more sociable compared with when the subjects were sitting a few computers apart.
Smell and emotion
Although we might not be aware of it, smells appear to affect our behavior, and perhaps can even be used to communicate emotions, research suggests.
Denise Chen of Rice University has compiled a growing body of evidence that humans can indeed communicate through odors, as animals are well known to do.
One study showed women's brains respond differently to men's sweat depending on the circumstances under which the sweat was produced. If the sweat was generated while the men were aroused from watching erotic videos, the women's brains were activated in regions responsible for recognizing emotions. No such pattern was seen in women's brains when they smelled sweat produced under normal circumstances.
Another study found that women who smell "fear sweat," sweat produced by men when they were watching horror films, are more likely to interpret ambiguous facial expression as fearful expressions.
More recent work from Chen revealed that the amount of time couples are together might affect their ability to interpret such odor cues. Chen and her colleagues recruited 20 heterosexual couples who had been together anywhere from one to seven years. The participants watched videos meant to elicit certain emotions: comedies for happiness, horror films for fear, erotic videos for sexual arousal and documentaries for neural emotions. The subjects wore gauze under their arms to collect sweat while watching the videos.
They were then asked to smell three bottles of sweat. Two were produced during the neural video, and one from one of the three emotional videos. The subjects had to identify the odd one out (the scent produced during the emotional video). The participants were more likely to identify the emotional sweat when it was produced by their partner rather than a stranger. And the longer the couples were together, the higher the accuracy.
The accumulating evidence suggests smell isn't just useful for detecting food, but "also for perhaps detecting the fine nuances of human social behavior," Chen said.
Smell and behavior
After hearing several anecdotal accounts of women holding on to bottles of baby powder for sentimental reasons — it took them back to the days when they were raising their children — Monique Smeets, also of the Utrecht University The Netherlands, wondered if certain smells could elicit nurturing behavior.
She had subjects watch an instructional video for parents depicting first-time parents interacting with infants. The room was scented with either a floral smell or a fruity one. Next, the subjects went into a different room (scented with either the same smell as the video room or another one) where they had to care for a baby doll designed to teach teens what it's like to have a child. The doll was equipped with sensors and provided nurturing scores based on how well the subjects performed as caregivers. The goal was to stop the doll from crying.
Participants who were exposed to the same odor twice (in the video room and the caring room) were more likely to receive the maximum nurturing score than those who were exposed to mismatched odors. That suggests their memory of caring for their own child, and the scent that went along with it, elicited better nurturing later with the doll.
The results agree with previous work that suggests smells are tied to behaviors. For instance, the cleaning smell of Windex has been found to be associated with virtuous behavior and purity, Smeets said.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.
Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.