Home » You Can’t Pick Your Friends’ Nose, But You Can Pick Your Friends With Your Nose

You Can’t Pick Your Friends’ Nose, But You Can Pick Your Friends With Your Nose

by Coffee Table Science

Image Credit: Weismann Institute of Science


Inbal Ravreby is a Ph.D. candidate at the Weizmann Institute of Science in the Department of Neurobiology. Recently, Inbal and her colleagues set out to answer the question: does the way we smell affect how well we click with someone? To do this, they recruited 20 participants and asked them to interact with each other, and describe the interaction after-the-fact. Each participant then donated their body odors by sleeping in a brand-new t-shirt for three nights in a row. The participants were required to use only unscented soaps and avoid any fragrant foods and perfumes that would convolute their signature body odor. 


The smells and chemical signatures left on the t-shirt after the three-day experiment were analyzed by an electronic nose and a recruited volunteer. The electronic nose confirmed that dyads (pairs of people in the experiment) who had clicked with each other tended to have similar odor chemistries. Similarly, the recruited volunteer smellers were able to identify click friends based on how similar their odors were at a rate greater than chance. Moreover, the study found that body odor chemistry can be used to predict click friendships with 71% accuracy, meaning body odor similarity can potentially predict clicking and future quality of the social interaction. For this edition of Researcher of the Month (RotM), we interviewed Inbal Ravreby, who recently published her work in Science Advances.


CTS: How would you describe “click friendship”?

IR: A strong sense of bonding that forms almost instantaneously. For the study, we asked 225 participants to define “click” and used a combination of their top 20 most frequent definitions.


CTS: Do you think the click friendship effect scales with potency? 

IR: I don’t know. Our results suggest the body odor similarity may predict clicking. Maybe people with a body odor that is more close to the average body odor have more clicks in their life, but this is just speculation and further research may answer this empirically. 


CTS: How useful do you think olfaction is in human interactions? 

IR: I think [the act of smelling] is very basic and we underappreciate its importance. Whereas in some cultures, odor processing is very explicit, social olfaction is largely without conscious awareness. Humans are constantly, but mostly subconsciously, sniffing themselves and their conspecifics. These odors then have a host of effects and may carry a host of information. For example: 


  • Sniffing women’s body odors may coordinate women’s menstrual cycles (although this effect remains debated)

  • Sniffing women’s tears lowers testosterone in men, which potentially alters behavior

  • Sniffing one particular molecule called androstadienone expressed in body odor raises levels of cortisol in women

  • Sniffing a different particular molecule expressed in body odor called hexadecanal blocks aggression in men but triggers aggression in women

  • Humans can infer a state of disease in body odor and can smell aggression, fear, stress, depression, and happiness in conspecifics. 

  • Body odor also serves as a cue for human kinship and influences human mate choice

In the current study, we add to this by finding that humans may use olfactory information to guide preferences in same-sex nonromantic dyadic interactions. We think our results imply that we may also be more like other terrestrial mammals in this respect than we typically appreciate.


CTS: What is your favorite part about working with human subjects?

IR: The best part is that we can ask for self-reports, so we have some access to the subjective experience. 


CTS: Now that you’ve conducted this research, are you more aware of how people smell when you interact with them?

I don’t really know, but I think that I am as I was before: not especially aware of humans’ body odors, but sometimes I do notice them, especially those of close friends (but this seems to be the case for most of us).


CTS: What sort of impacts do you hope these findings have on the general public?

IR: I hope people will appreciate more the role that non-verbal cues play in our lives, and among them even subconscious ones. Additionally, I hope people will better appreciate the sense of smell and, more importantly, remember that we have a lot in common with other mammals and that there are many shared mechanisms. We sometimes tend to think about ourselves as a totally different animal from all the others and I think this is not the case, at least in some aspects. 


CTS: Where might the findings of this research have the largest impact?

IR: I would suggest starting with olfaction-based paths to intervention in social impairment of normosmics (people with normal sense of smell). Maybe in the future, the body odor similarity would be taken into account when dividing people into teams in workplaces, for example, and this may improve the teams’ performances. But I would suggest further research in these directions before implementing them.


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