The video explores the fascinating biological and emotional purpose of tears, particularly focusing on emotional tears as opposed to those for ocular maintenance. Drawing on Charles Darwin’s observations, it discusses the challenges scientists face in explaining tears’ functional antecedents. Although disgust and aggression expressions have been traced to evolutionary survival mechanisms, tears remain enigmatic as they do not have a clear antecedent. Researchers have started considering tears as a possible chemical signal used for non-verbal communication under specific emotional states.

This is a compelling exploration as the researchers delve into various studies aiming to uncover the mysterious functions of tears. Emotional tears might cause hormonal changes, such as lowering testosterone levels and decreasing aggression, suggesting a powerful chemosensory role. The study reveals some inherent gender bias as volunteer tears donors were predominantly women, with fewer male participants due to cultural factors affecting men’s willingness to express vulnerability. The discussion also touches on technological and biological hurdles scientists face when conducting such experiments, like ensuring ethical research practices and experimental replication.

Main takeaways from the video:

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Key Vocabularies and Common Phrases:

1. ocular ['ɒkjələr] - (adjective) - Related to the eye. - Synonyms: (optic, visual, ophthalmic)

But he bothered to write this entire chapter on the ocular sort of maintenance function of tears and so on and so forth.

2. antecedents [,æntɪ'siːdənts] - (noun) - Preceding events or circumstances that influence what comes later. - Synonyms: (predecessors, forerunners, predecessors)

Because the book revolves around describing the functional antecedents of emotional expressions.

3. aggression [əˈɡrɛʃən] - (noun) - Hostile or violent behavior or attitudes toward another; readiness to attack or confront. - Synonyms: (hostility, anger, belligerence)

So, for example, showing of the teeth as a sign of aggression

4. disgust [dɪsˈɡʌst] - (noun) - A feeling of revulsion or strong disapproval aroused by something unpleasant. - Synonyms: (repulsion, distaste, revulsion)

The emotional expression of disgust.

5. hypothalamus [ˌhaɪpəˈθæləməs] - (noun) - A region of the brain that controls the autonomic nervous system and pituitary gland, affecting emotional activity, hunger, and thirst. - Synonyms: (brain area, neural section, regulatory center)

And saw pronounced if effect on activity a dampening, a lowering of activity both in the hypothalamus and in the fusiform gyrus.

6. oxytocin [ˌɒksɪˈtoʊsɪn] - (noun) - A hormone involved in childbirth and breastfeeding associated with bonding and emotional connection. - Synonyms: (bonding hormone, love hormone, neurotransmitter)

I think that dogs, perhaps through oxytocin, hijack the circuitry that's intended for child rear.

7. narrative distancing ['nærətɪv ˈdɪstənsɪŋ] - (noun phrase) - The psychological distance between individuals and the narrative content of a media experience. - Synonyms: (psychological detachment, cognitive separation, mental division)

They call it narrative distancing.

8. chemosensory [ˌkiːmoʊˈsensəri] - (adjective) - Relating to the detection of chemical stimuli through the senses. - Synonyms: (chemical sensing, olfactory sensing, sensory detection)

Storey it points again to the power of these chemosensory systems.

9. magnanimous [mæɡˈnænɪməs] - (adjective) - Very generous or forgiving, especially toward a rival or someone less powerful. - Synonyms: (generous, altruistic, benevolent)

And I do appreciate that you published the rebuttal and that you offered in a very magnanimous way to do a collaborative.

10. seditious [sɪˈdɪʃəs] - (adjective) - Inciting or causing people to rebel against the authority of a state or monarch. - Synonyms: (rebellious, insurgent, revolutionary)

I'm going to think of that as the seditious, the titration, the sadist titration.

Why We Cry & the Evolutionary Purpose of Tears - Dr. Noam Sobel & Dr. Andrew Huberman

We started thinking about tears and looking into tears because tears are a bodily liquid, emotional tears that we emit in emotional situations where these are situations where nonverbal communication is critical and key. And tears are a liquid that is puzzling beyond ocular maintenance. Right.

And so, you know, the most influential text, I think, till this day in emotion research is Darwin's book, the Showing of the Emotions in Man and Animals, I think is the full name of the book. And an Entire Chapter, Chapter 6 is devoted to tears. An entire chapter of this book. Why? With no conclusion, why? Because the book revolves around describing the functional antecedents of emotional expressions. So, for example, showing of the teeth as a sign of aggression. Right. So animals first bit with their teeth. And Darwin argued that through evolution, just showing the teeth alone became an aggressive sign because it started from biting.

Or what I find is a beautiful example, and this is work partly done by Adam Anderson now at Cornell, is the emotional expression of disgust. disgust, which comes from the line dysgusia distaste, is spitting something out of your mouth. Now, what Adam showed is that the musculature patterns of activation and the temporal sequence of activation when you experience moral disgust are the same as when you spit a bitter taste out of your mouth, right?

So again, so there's a functional antecedent spitting something out. And through evolution, the argument was that it became an expression of emotion and you express disgust just as if you're spitting something out of your mouth, even though there, you know, in the case of moral disgust, there's nothing you're spitting out of your mouth. So darn systematically went through the expressions of emotions and for each one, went to their functional anticipant and explained everything very nicely.

And then he got stuck with tears, right. Because tears are an obviously emotional expression and he could not find a functional antecedent. So he ended up saying, this is an epic phenomenon, basically. Right. I don't know what all scientists do when they don't have a good explanation. Blame it on nature. Right, right. But he bothered to write this entire chapter on the ocular sort of maintenance function of tears and so on and so forth, but nothing emotional.

So we thought, well, maybe the function is a chemical signal. And so with that in mind, we harvested emotional tears, which was also an amusing event on its own, Right. Because we posted messages on all sorts of boards that we're seeking experiment participants who cry with ease. Now, this generated an unfortunate gender bias in our study, right. Because we received about 100 women volunteers and about one man.

And, you know, I Think this is not a problem. Only in macho Israel. Right. Probably anywhere in the west this would. I mean, definitely in America it would be the same. I think my guess is that there are probably men out there who cry easily. Emotional tears. Oh, I'm sure. But they're not going to show up. Yeah, yeah, that's what I'm saying. It's a cultural thing. It's not, you know, you're not going to come to a lab and say, you know, I cry all the time, it's just not going to happen.

And then what we did is for each one of these participants, we would ask them, is there a particular film event that you know of that a scene that makes you cry? And interestingly, in these effective criers, there's always. Oh yes, you know, the scene in so and so. I always cry profusely from that. You know, they have.

Can you give me an example of one of the more commonly named scenes? Yeah. With these. The movie the Champ. The champ dies. He's a boxer and he dies and literally in the hands of his about 8 year old son, and his son is standing next to his bed and you know, saying, champ, champ. And he dies. Right. It's a winner. Okay. Waterfalls. Yeah, yeah, got it.

So, you know, we're probably the neurobiology lab with most sad movie films on the shelf in the world, right. We have a whole huge collection. There is such a thing as tears of joy, by the way. So. No, no. Well, we're going ahead of ourselves. But I say we tried to collect them and failed. Even people who think they shed tears of joy and laughter, their eyes water a bit. But it's not the same thing.

In the effective criers we end up screening. So we collect a full ML of tears, a full ML of tears in about 15 minutes. So that's pouring, Right. And that doesn't happen from laughter or. We've never seen that. We've never seen that happen from laughter. We tried. So we have all these sad films and by the way, one of the amusing things is when we ultimately published this paper in science, we were forced in retrospect to go out and actually buy the films. Right.

I mean, you know, originally we like downloaded them, but you can't because you'd be violating, you know, copyright laws. Right. So we had to buy like purchase all these films that the participants and watch them. So we actually have these in lab, like DVDs, you know, that we actually purchased. But so nice coverage of potential legal fallout there. No, no, no, no, we did. We did so.

Yeah. And. Well, we can touch on that later. But so we. So most of these volunteers who come saying they can cry with ease actually don't meet the bill. And so out of the about hundred, at least more women that we screened, we ended up with about six who could really come to lab week after week. And poor tears.

There's a name for this in psychiatry. They call it narrative distancing. Some people, when they watch a film where someone's getting hit, they flinch quite a lot. It's almost as if they're experiencing it. But it works in the opposite direction, too. I know someone like this where if they watch a film that someone's experiencing something even mildly positive, their mood elevates, so they can quickly bridge. And it's not always adaptive, as you can imagine. So there's lack of narrative distancing, Right?

Yeah. One issue you can bring up with this entire line of studies in our lab is I don't know if there's something very unique about the donors. Right. I mean, we're assuming these are tiers. No, this is pretty common. I think that the numbers I saw out there, about 5 to 8%. That's exactly what we got about. Right. About 6.

So we collected tears and we exposed participants to these tears. And we found a few things. First of all, the tears are completely odorless. You cannot detect them at all. Completely odorless. And yet when you sniff them, you have a pronounced reduction in Testosterone within about 20 minutes, half an hour.

This is men and women smelling women's tears. Men, women's tears, but not perceiving any odor. Nothing. Just sniffing them. And you have about 14% drop in free testosterone. Free. Okay. So this is testosterone that's already been liberated from the testes. Free testosterone. Or that we've done a few.

Hormone that's either bound or unbound is unbound. Excuse me, from sex hormone binding, globulin, et cetera. And it's the active form, so it's subject to very short timescale changes. Yeah. And this is people who study testosterone, which is not me, but they tell me this is a really strong effect. It's hard to even pharmacologically get an effect like that that fast. I mean, known pharmacology.

Yeah. Years ago, I spent time studying endocrine effects of this sort. And that's a tremendously sized effect. And so here I'll point out in passing that one of the concerns we had because of the effort to run this study is that nobody would ever try to replicate it. And to our joy, about two years later, an independent group from South Korea, O et al. Who I don't know at all replicated the testosterone effect to a T. I mean like same numbers. So.

So it. It lowers testosterone and. And we then also looked using Mr. At the. @ the effect on brain activity and saw pronounced if effect on activity a dampening, a lowering of activity under an arousing state, a lowering of activity both in the hypothalamus and in the fusiform gyrus for whatever reason. I don't know. Amongst other things.

Yes. And we don't know why but pronounced and currently chenille are growing in our lab is replicating this again and this time with a stronger behavioral component. And I can share with you unpublished data now under review that as you would expect, given the effect on testosterone, perhaps sniffing tears lowers aggression in men using again the tap, the same experiment used by Eva in the hexadecanal experiment. I'm going to think of that as the seditious, the titration, the sadist titration. Yeah, Tyler aggression paradigm.

Not unlike the Milgram experiments of the 1950s which post. This was looking at sort of post holocaust behavior. People basically in American laboratories thinking they were torturing other people simply because they were told to. And a lot of people did that. Even though most people would report that they would never torture someone. Yeah, yeah. No, humans are not a wonderful species or as we could say, I think it was the great Carl Jung that said that we have all things inside of us, but the goal is not to experience them all.

Certainly it's an incredible study and it points again to the power of these chemosensory systems and pathways. And obviously there's so much here. I don't know if you want me to tell about this or not and I guess you can edit it out if you don't, but please, this is just sharing stories about the politics of science. Whereas the effect on testosterone was replicated by an independent group in the original study in science where we had.

It had three components. One was the effect on testosterone, which was robust. The second which was brain activity which was robust. And there was a significant but weaker effect on behavior. And I don't think we studied the right behavior in retrospect. What we looked at then was ratings of arousal associated with pictures. And there was an effect. It was significant, but it was not what carried the story.

Now there's a lab in Holland of a guy by the name of. I'm probably mispronouncing this, but I think it's wingerhoats for the non Dutch. Yeah, Dutch names are always a little bit of a challenge. But. And I shouldn't say that being an Israeli, I shouldn't go too much on that line. But, but that lab really didn't like our original tear story. And the reason they didn't like it is because they've built a career on this notion, including a book with this title, that emotional tears are uniquely human.

Now here I should. Well, I should share. So one of the things we really liked about the tier result is that partially before we did our work, but more afterwards. And we like that because usually things. So usually in our chemo signaling work, like what I told you before about the Bruce effect, we look at what happens in rodents and we see if the same thing is happening in humans.

This was a rare case where after we did this work, more or less identical effects were discovered in rodents. So a paper published in Nature two years later found that mouse tears, mouse pup tears, lower aggression in male adult mice towards them in a smell dependent way. Yeah, yeah. And they also actually found the actual component in tears that. So the tear pheromone that lowers aggression. Right.

So, you know, this has us thinking of aggression as tears as you can think of tears as like a chemical blanket in a way that you're covering yourself up again with, you know, to protect against aggression. Right. And, and so our finding, you know, which to me, I mean, this is consistent with how I think about behavior in general. You know, I don't think, you know, beyond language, there are very few things, definitely sensory things that are uniquely human.

You know, I'd be hard pressed, but. So, you know, our finding went against, you know, against their story. Right. Because you know, here we're saying no, you know, tears are this chemo signaling mechanism like all animals. And by the way, just after this entire debate, about six months ago, there was a paper in current biology that dogs emit emotional tears and dogs emit emotional tears when they reunite with their owners.

And you were talking before about oxytocin. So I think what they showed there is that not only that, but that the view, seeing the tears in the dog influences oxytocin in the humans. I hope I am getting this right. I absolutely believe this. From the time I brought Costello home at eight weeks old. Costello's your dog? He was my dog. Unfortunately passed away, but hadn't been a long time.

Actually the only time I can recall crying. Listen, I've certainly cried before many times in my life. Many, many times. The only time I ever recall crying to the point where I wasn't sure that I could keep producing tears but somehow did is when I had to put him down. Right. It's just like, you know, and if I talk about too long now, I'll start trying to, you know, it's one of those things. I think it's a healthy emotional state for sure.

But I recall when he was a puppy thinking this oxytocin thing must be real because I can recall being in faculty meetings which, you know, very fairly stated, are not always that interesting, but they could be pretty interesting. And someone presenting data in my mind thinking, I hope Costello is okay. What's he doing down in my office? This is when he was very little and also not needing to eat, not being able to focus on anything else except my attachment to him for about the first two or three weeks that I had him.

Then it was easy, then I could focus off on other things. And I think that dogs, perhaps through oxytocin, hijack the circuitry that's intended for child rear. I really do. Otherwise why would people be so ridiculously attached to their dogs? I mean, hence all the posts of everyone thinks their dog is the cutest dog, the same way everyone thinks their children are the cutest children. You know, customer, by the way, was a very handsome bulldog.

So, yeah, so again, so even, you know, to put another nail in that story of tears are uniquely human. So they're not dogs shed emotional tears. And so that group really didn't like this and they went ahead and tried to replicate. And to your listeners, I'm showing double quotations on the replicate, only the behavioral part, the ratings of arousal in women, of women, and failed to replicate that.

I see now this was just sharing on how science works and doesn't work in my notion in this case. So at the time, after they got this accepted in some journal, not a field journal, in the Journal of Memory of something, they contacted me for a response and I wrote to the authors and I said, look, this is very odd to me. Why don't you come? Why don't we replicate this again together and see if it doesn't work? If it doesn't work, I'll publish it with you that it doesn't work. And so I said, why don't you send over a graduate student or the lead author and we'll do it here and we'll show them how it's done because they did it very wrongly in the paper. They replied that no, they don't have money to send over graduate student to do it.

So I replied saying, okay, I'll fund the graduate student coming over and I'll fund the entire study and their stay and so on and so forth and let's do this together. And they replied, no, they're not willing to do that, which I don't think is the way things should work. And they published this sort of failed behavioral effect in that paper. So I'm just sharing this, that it's not only there was that successful replication with the effect on testosterone, but there was supposedly this failed replication on the effect effect in behavior.

And then I published a rebuttal on that, which I don't know if I should have done, but I did. Well, I think it's interesting. I think provided studies are done correctly, I mean, the positive result almost always trumps the negative result. And yet I think replication is key. The problem, as you pointed out, is that replication is rarely pure replication of the exact study. This one is not even remotely, but. And I published the detail.

So actually they hid something in their data that did partially rip. So I asked for their data, and I reanalyzed it, and that's what I published in the rebuttal. But, you know, this is just sharing on how science works. I took advice. So it's not that I'm friends with him, but at that time, I was communicating a bit because we were on some board with Daniel Kahneman, who's Nobel laureate, working fast and slow, right? And so I asked him, how should I deal with this? You know, give me some advice here. I was really, you know, it was emotionally not fun to be in that position.

And he said, don't, don't, don't. Never publish a rebuttal. Don't do anything. And I was, you know, how can I, you know, I have to do something. He said, no, don't, because once you do that, then, you know, people don't go into the details. They won't read the details of your rebuttal. They'll be like, well, there's a group that says this and there's a group that says that. So it's unclear. Well, I mean, I appreciate that you're bringing it up today, and I do appreciate that you published the rebuttal and that you offered in a very magnanimous way to do a collaborative. That's what he then said. So Kahneman's advice after that was that, well, if you insist, then just publish. Write a response that you offered them to come do it together. They refused, and there's nothing you can do about that.

Science, Innovation, Technology, Emotional Tears, Non-Verbal Communication, Cultural Influences, Huberman Lab Clips