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# Always Smelling You: Neuroscientist Noam Sobel on the Hidden Chemistry of Handshakes, Friendship and Tears
- URL: https://longtalkshort.com/noam-sobel-smell-handshakes-tears-chemosignals/
- Published: 2026-10-29T16:35:08.000Z
- Updated: 2026-10-29T16:35:08.000Z
- Description: Noam Sobel shows humans constantly smell each other: we sniff our hands after handshakes, click friends smell alike, tears lower testosterone and a baby molecule calms men but rouses women.
- Author: Truman
- Tags: Science, Noam Sobel

**After you shake someone's hand, you'll probably sniff your own hand without noticing.**

Dogs sniff each other openly. Humans, we like to think, don't. Noam Sobel, a neuroscientist at Israel's Weizmann Institute, has spent years showing that **we do, just more discreetly.** With Andrew Huberman on Huberman Lab Essentials, he goes from the wiring of the nose to handshakes, friendship, tears and a molecule babies give off, and ends with the first smell sent over the internet.

> People are constantly smelling themselves, constantly smelling others.

*In short: humans give off chemical signals that change other people's behaviour and hormones, mostly without anyone noticing. Sobel's lab has measured several of them, and is now trying to digitise smell itself.*

## 1\. How the nose is wired

Airborne molecules travel six or seven centimetres up the nose to the olfactory epithelium, a heavily folded sheet that Sobel says holds about six or seven million receptors of roughly 350 kinds, **a large share of our genes given over to one sense.**

- **Each receptor type** responds to a few molecular features.
- **All receptors of one type converge** on one spot in the olfactory bulb, a glomerulus. Sobel calls this "the most extreme case of convergence in the mammalian nervous system." So coffee lights up a pattern on the bulb, a kind of map.
- **From there, "it goes all over the brain":** to the piriform cortex, and directly to the amygdala and, probably, the hypothalamus. Past the bulb, the neat map seems to vanish and the coding is, in his word, "murky."

**Those direct links to emotion and hormone centres help explain why smell can act on us below awareness.**

![Route from nose to brain: receptor neurons in the nose lining, glomeruli in the olfactory bulb, then piriform cortex, with branches to amygdala, hypothalamus and entorhinal cortex](https://storage.ghost.io/c/d7/93/d793216c-cf13-441f-bdae-4f3aef998c0e/content/images/2026/10/fig1-42.png)

The route from nose to brain, simplified. Our diagram. Made for Long Talk Short.

## 2\. Handshakes and "click" friends

The usual story, that shaking hands shows you aren't holding a weapon, has "no good evidence," Sobel says. His lab, in a study led by Idan Frumin, filmed people covertly while they waited alone, then had a new experimenter greet them with or without a handshake.

- **After a handshake, hands went to faces far more often.**
- **Hidden airflow sensors showed real sniffing,** not just touching.
- **People also sniffed their other hand,** which Sobel reads as comparing self with other.

A second study, led by Inbal Ravreby, recruited same-sex friends whose friendship began with an instant "click." Each used odourless soap and slept alone in a T-shirt; an electronic nose compared the body odours. **Click friends smelled more alike than random pairs,** and human sniffers agreed. To test cause, she sampled strangers first, then had them play a silent "mirror game." Odour similarity didn't predict how well they mirrored each other, but **it did predict how much they liked each other.**

> We could actually predict friendship using the electronic nose

![Four cards summarising studies from Sobel's lab: handshakes (2015), click friends (2022), emotional tears (2011 and 2023) and hexadecanal (2021)](https://storage.ghost.io/c/d7/93/d793216c-cf13-441f-bdae-4f3aef998c0e/content/images/2026/10/fig2-31.png)

Four findings from Sobel's lab discussed in the episode. Our diagram. Made for Long Talk Short.

Then the lab turned to tears.

## 3\. Tears and a baby's chemical shield

Sobel avoids the word pheromone ("it would probably only hurt us") and says **chemosignals** instead. The best known is the smell of fear: body odour from frightened people raises arousal in those who smell it. His own lab's results are stranger.

**Tears.** Darwin couldn't find a function for emotional tears, so the lab collected them. They had no detectable smell, yet men who sniffed women's tears showed, he says, about a 14% drop in testosterone within half an hour. A later study found the same tears lowered men's aggression in a lab game. He calls tears "a chemical blanket" against aggression.

**Hexadecanal (HEX),** a molecule studied in mice by Heinz Breer, has a receptor highly conserved across mammals. Graduate student Eva Mishor tested it in a standard lab aggression game:

- **In men,** HEX reduced aggression.
- **In women,** it increased it, and the result held again inside a brain scanner.

The explanation came later. HEX is, Sobel says, the most abundant semi-volatile coming from babies' heads. Fathers and other males are a common danger to infants; mothers' aggression is often protective. **A molecule that calms men and makes women fiercer helps the baby either way.**

> Babies are conducting chemical warfare.

## 4\. Sending a smell over the internet

In a *Nature* paper led by Aharon Ravia, the lab built a model that **predicts how similar any two mixtures will smell,** good enough to design olfactory metamers: mixtures with no molecules in common that smell the same. With a map of about 4,000 molecules, Sobel says, any new mixture can be placed and its smell predicted.

Next came transmission. Atmospheric chemist Jonathan Williams measured four odours in Germany and sent the data online to Israel, where a device mixed them from a small set of primaries:

- **Rose** came out as bubble gum; **anise** as cherry.
- **Gasoline** was only slightly better than chance.
- **Violets worked:** 15 of 16 people named them.

Sobel calls the stage "circa 1956 black and white TV." At "4K" quality, he imagines an electronic nose in every toilet running constant medical diagnostics, though not for decades.

## Weighing it: what holds up

**The studies exist and say roughly what he says:**

- **Handshakes:** Frumin and colleagues, *eLife* 2015, covert video of 271 people.
- **Click friends:** Ravreby's "There is chemistry in social chemistry," *Science Advances* 2022, with the electronic-nose and stranger findings.
- **Tears:** Gelstein's 2011 *Science* paper reported lower salivary testosterone and sexual arousal in men sniffing women's tears; we didn't confirm the exact 14%. Agron's 2023 *PLOS Biology* study reported a 43.7% drop in aggression in 25 men.
- **Hexadecanal:** Mishor, *Science Advances*, November 2021.
- **Metamers:** Ravia, *Nature* 2020, based on nearly 50,000 similarity ratings.

**Caution:** an independent 2017 replication found no tear effect on men's ratings of women's attractiveness, so not every result has held up. **Many effects come from small lab samples;** treat effect sizes as provisional.

**One correction:** the lab's EU-funded D2Smell project places the sending end of the odour test in Mainz, not Munich as Sobel says.

**Not checked:** the receptor counts, the 15-of-16 violet result, the Korean replication of the testosterone effect, the mouse-tear paper and the study on dogs smelling human fear.

**Related reading:** for another look at how the brain shapes feelings before we're aware of them, see [Your Feelings Are Guesses](https://longtalkshort.com/lisa-feldman-barrett-your-brain-is-guessing-emotions-predictions/).

## Long Talk Short

- Smell wires directly into emotion and hormone centres, so it can shape behaviour before we notice.
- After a handshake, people sniff their hands, a covert way of sampling each other.
- Friends who clicked at first meeting tend to smell alike, and odour similarity predicted liking between strangers.
- Odourless emotional tears lowered men's testosterone and aggression in Sobel's lab, though not every replication agrees.
- Hexadecanal, abundant on babies' heads, calmed men and made women more aggressive, protecting the infant either way.
- The lab can predict how mixtures smell and has sent a recognisable violet over the internet.

**The one thing to remember:** some of what you call a gut feeling about a person may be chemistry. You're always smelling each other, whether or not you notice.

Source: ["Essentials: How Smells Influence Our Hormones, Health & Behavior | Dr. Noam Sobel"](https://www.youtube.com/watch?v=arMMF0ISRRM&ref=longtalkshort.com), Huberman Lab Essentials with Andrew Huberman. This is an independent summary and is not affiliated with Huberman Lab, Dr. Sobel or the Weizmann Institute.

*Quotes are taken from a machine transcript because captions were unavailable, and may contain small transcription errors. This article is for general information only and is not medical advice.*