We started thinking about tears and looking into tears because tears are 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. And so 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 is 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. So disgust, which comes from the Latin disgusia, distaste, right, 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 in the case of moral disgust, there's nothing you're spitting out of your mouth.

So Darwin systematically went through the expressions of emotions and for each one went to their functional antecedent 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?

What all scientists do when they don't have a good explanation, blame it on nature. Right, right. So, 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 were seeking experiment participants who cry with ease. Now this generated an unfortunate gender bias in our study, right? Because we received about a hundred 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 be, I mean, definitely in America would be the same, I think. My guess is that there are probably men out there who cry easily, emotional tears easily. Oh, I'm sure.

But they're not going to show up. 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, you know, we would ask them, you know, is there a particular film event that you know of that, you know, 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 their- Can you give me an example of one of the more commonly named scenes? With these, the movie The Champ. The Champ dies, he's a boxer.

And he dies and literally in the hands of his about eight-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. Waterfall. 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. Like I said, 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 copyright laws, right?

So we had to buy, like purchase all these films that the participants watched. So we actually have these in lab, like DVDs, you know, that we actually purchased. Nice coverage of potential legal fallout there, Noam. No, we did. We did. I believe you. I believe you. So, yeah. And, well, we can touch on that later.

But 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 in poor tears.

There's a name for this in psychiatry. They call it a 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 a lack of narrative distancing. Right. Yeah. Well, 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 tears. No, this is pretty common. I think that the numbers I saw out there, about 5% to 8% of people got about 600. 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. Just men. Men smelling women's tears, but not perceiving any odor. Nothing. Just sniffing them.

And you have about a 14% drop in free testosterone. Free. OK, so this is testosterone that's already been liberated from the testes. Free testosterone. We've done a few hormones 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. No one in pharmacology. Yeah. Years ago, I spent time studying endocrine effects of this sort.

And that's a tremendously sized effect. 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, OHL, who I don't know at all, replicated the testosterone effect to a T.

I mean, like, same numbers. So it lowers testosterone. And we then also looked, using MR, at the effect on brain activity and saw a pronounced 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.

Face recognition area. It's other things, yes. And we don't know why, but pronounced. And currently, Shania Groen 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's, 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 Yvonne in the hexadecanol experiment. The TAP, I'm going to think of that as the SATIS, the titration, the SATIS titration experiment. The 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 somebody else. Yeah, no, humans are not a wonderful species. Or as you could say, I think it was the great Carl Jung that said, 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. This is just sharing stories about the politics of science.

So whereas the effect on testosterone was replicated by an independent group. In the original study in science, 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 is a lab in Holland of a guy by the name of, I'm probably mispronouncing this, but I think it's Wingerhoets.

For the non-Dutch. Yeah. Dutch names are always a little bit of a challenge. And I shouldn't say that, being an Israeli, I shouldn't go too much on that line. 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 tear 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.

So 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 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 so our finding, you know, which to me, I mean, this is consistent with how I think about behavior in general. I, 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 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, you know, just after this entire debate, about six months ago, there was a paper in Current Biology that dogs emit emotional tears. And it was the 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 of seeing the tears in the dog influences oxytocin in the humans. I hope I'm getting this right. No, I absolutely believe this. I mean, from the time I brought Costello home at eight weeks old.

Costello is your dog. He's my dog. Unfortunately, he passed away. We haven't had him in a long time. But from the 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 it is when I had to put him down, right?

Is this like, you know, and if I talk about too long now, I'll start crying. You know, it's one of those things. I think it's a healthy emotional state. 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, fairly stated are not always that interesting, but they can be pretty interesting.

And someone presenting data and 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 rearing. I really do. Otherwise, why would people be so ridiculously attached to their dogs? Hence all the posts of everyone thinks their dog is the cutest dog, the same way everyone thinks their children are the cutest children.

Costello, by the way, was a very handsome bulldog. 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 of women and failed to replicate that.

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, a journal of memory of something, they contacted me for a response. And I wrote to the office and I said, look, you know, 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, but you know. 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.

And so they replied that no, they don't have money to send over a graduate student to do it. So they 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, you know, 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 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 mean, 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 I published the detail. So actually they hid something in their data that did partially work. 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. 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 ever 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, and yeah, 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 collaboration. 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.