Key Takeaways

  • Neurobiologist Dr. Noam Sobel and lead researcher Idan Frumin discovered that humans use handshakes to secretly sample chemical signals from others.
  • Secret video recordings showed that subjects touched their faces far more often immediately after greeting a new experimenter with a handshake.
  • By measuring nasal airflow, the researchers confirmed that participants were actively inhaling through their noses rather than simply scratching their skin.
  • Chemosensory sampling happens outside conscious awareness, transferring molecules that influence aggression, emotional states, and friendship formation.

The Covert Olfactory Test

Dogs greet each other by sniffing directly. Humans do not walk up to business partners and openly inhale their scent. As Sobel observed, society limits obvious smelling: “And yet, humans don't typically walk up to a stranger and carefully sniff them, right? I mean, it's We're we're sort of obliged to sniff our our babies. That's considered almost something you're supposed to do.”

Because open sniffing is socially unacceptable between adults, biology found a workaround. Sobel noticed an odd pattern during ordinary greetings: “And we started looking at people handshaking, and and we noticed, or it seemed to us that we're noticing that you know people will shake hands and then we'll go like this and like.”

To test whether people were actually collecting chemical information, Idan Frumin set up a controlled experiment. Researchers placed participants alone in a room and filmed them secretly to measure baseline face-touching behavior. Then, a new experimenter entered the room. Sobel explained the design: “And half of the cases it included a handshake. This was a new experimenter, not the one who put them in the room. So that's the first time they met.”

Measuring the Covert Sniff

The cameras captured a dramatic shift in behavior the moment the greeting ended. When the experimenter shook hands, subjects brought their right hand up to their face at a rate far higher than the baseline period. As Sobel put it: “And there was a remarkable increase in the hand going to the nose after handshake. It's unreal.”

Touching the nose is not proof of smelling. Skeptics could argue that meeting a stranger causes nervousness, and nervous people touch their faces. The research team anticipated that objection and tracked breathing directly.

Sobel explained the technical confirmation: “One is unbeknownst to anti-participants we measured nasal airflow. And and and people not only bring their hand to their nose, they sniff it.”

The nasal airflow sensors registered a distinct spike in air volume entering the nostrils whenever the hand hovered near the nose. Subjects were inhaling molecules deposited on their palms during physical contact. They were sampling chemical signals to compare self and other. These transferred molecules regulate hormones, temper aggression, and shape whether two people form a bond.

Remote video calls eliminate this data channel entirely. You can evaluate slide decks, pitch cadence, and facial expressions over a screen, but you cannot sample biological signals through a webcam.

What to Do With This

Schedule your final candidate interviews and major partner negotiations in person, and always open with a standard handshake. Pay attention to your own involuntary physical movements right after you sit down at the table. If you find yourself resting your chin on your hand or rubbing your nose, recognize that your nervous system is actively processing biological data about the person across from you.