Spooky True Crime Vol. 4: The Neuroscience of Serial Killers

0:00No one goes to Hank's for his spreadsheets. They go for a darn good pizza. Lately, though, the shop's been quiet. So Hank decides to bring back the $1 slice. He asks Copilot in Microsoft Excel to look at his sales and costs and help him see if he can afford it. Copilot shows Hank where the money's going and which little extras make the $1 slice work. Now Hank's has a line out the door. Hank makes the pizza. Copilot handles the spreadsheets. Learn more at m365copilot.com slash work.

0:30USAA knows dynamic duos can save the day, like superheroes and sidekicks or auto and home insurance. With USAA, you can bundle your auto and home and save up to 10%. Tap the banner to learn more and get a quote at usaa.com slash bundle. Restrictions apply. The image had been de-identified, so he didn't know which family member it belonged to, and that's pretty standard in medical studies because you don't want the researcher to be biased, and, like, especially if he's dealing with images of his own family's brains.

1:01You don't want him to know exactly who it is or else it might affect his interpretation. But for this case, he was like, well, shit, like, someone in my family is a psychopath based on this brain scan. So he decided to check to see whose brain it was and, like, break the blinding that was in place. And turns out it was his own brain. I'm Paige. And I'm Megan. And this is Spooky Science Sisters.

1:30Hello, you're listening to Spooky Science Sisters, a podcast where we present to you a science-based and probably very giggly discussion on all things strange and unusual. And our strange topic for the day is spooky true crime, which is our fourth round of Spooky True Crime. I feel like this one is maybe the least uplifting of all of them. If that's possible. I don't know if any of the spooky true crimes have been uplifting.

2:02What's the opposite of uplifting?

2:06Because it's the most of whatever that is. Yeah. It's a little bit of a heavy topic, but yeah. What are we going to talk about today, Paige? We are going to talk about the science of serial killers. Yay!

2:25It doesn't feel right to say yay. Yay. It's fine. That's what I'm going to do every time. Yeah. Which is a topic that I have had, like, written down as an idea for the podcast, I think, since the beginning. And now we're finally doing it. So it's interesting, but yeah, it's a lot. Yeah. There's a lot there, and it's a heavy topic, so. Yeah. That's fine. That's our specialty. Okay. So first, before we talk about serial killers,

2:57some reminders. We wrote a book. I'm sure you guys are getting sick of hearing about it, but that is too bad. It is called Spooky Science, Dissecting the Mysteries of Ghosts, Cryptids, Aliens, and Other Oddities. If you have the book and you've read it and you've enjoyed it, it would be super awesome if you could leave a review somewhere. Goodreads is obviously an option, but wherever you want to do that helps us out, so that would be great.

3:27We do have some upcoming events on October 4th, which is coming up in just a few days, and hopefully if I get this out by Friday of this week, it will be tomorrow for those of you listening, but we will be at the Southport Literary Fair in Kenosha, Wisconsin, and I think that event runs from 11 a.m. to 4 p.m., maybe 5 p.m. Yeah. I think it's 4.

3:58I think it's 4 p.m. But anyway, we'll just be hanging out at a table and talking to people, and we'll have little goodies to hand out. And yeah, so if you're around, you can come see us. Then on October 30th, we will be doing Skeptical Inquirer Presents, and we're going to talk about some monsters, and specifically vampires, and that will be a virtual event, so we will, as soon as we have it, give you guys the link to where you can watch that as we do it.

4:28So watch us be the most scared we've ever been this entire time. Yes, those are the major things. There's a couple other things floating around, but we'll let you know. Okay, so that's book stuff. That's intro. We have to do something spooky. So Paige, has anything spooky happened to you slash you want to remind people about what we need from them? Yeah, so I was going to say, I don't really have a something spooky, or maybe I do, and it's just lost. My brain, I feel like,

4:59has been melting for the last couple weeks, and I don't know what's happening anymore. Maybe that's my something spooky, but what I do know is that Halloween is like a month away, which is wild, and because of that, we are going to be recording our annual Halloween listener story episode soon. So for those of you who have been listening for at least the last year or two know the deal, but for those of you who are new listeners, every year we do an episode where we get stories from you,

5:32and they can be like ghost stories or just something you want us to read and share, debunk, think about, talk about, and then we do like a live, I don't know. I guess it's not live, but it's a... It's live for us. It's a special reaction. Yeah, it's live for us. So you get like our real like first read through, and then we share it with everybody. So if you have a story you want us to share, like I said, we can debunk it if you'd like us to. Or if it's something that spooky

6:03that happened to you that you debunked, you can also share it. Yeah. Because those are fun too. We will be recording that. I don't know. I would say if you have a story you really want us to look at, like probably by October the 20th, then yeah, you can send those to us via email. If you are following us on Instagram or Facebook, you can share it that way. However you want to share it with us is fine. And then we will take a look at it and put it in this year's episode.

6:35Yeah. We're behind collecting them. Normally we've announced this like twice by this time of year, but here we are three weeks ahead of time. That's okay. It's fine. It's fine. We're doing it. Yeah. Okay. Well, I do have something spooky. Yeah. Sorry. I didn't ask. No, that's fine. How dare you? No, I do have something spooky. So we have been watching the Alien Earth show,

7:05which just wrapped up its first season like a week ago. And really enjoying it. But it was, I think a couple of weeks ago, my husband and I were watching the episode. And all of a sudden we started to hear what sounded like footsteps, like in our upstairs part of our house. Cause we were down in the finished basement watching stuff, but it's sort of, it's like an open stairwell to upstairs. And we definitely thought that our six-year-old was out of bed. And we're like, oh shit.

7:36Like we got to go check that out because we really do not want her to walk down in the middle of this show and ruin her entire life. However long it would take to recover from how traumatic part of that show would be for a six-year-old. So anyway, we heard it and we went upstairs and started looking around and Alice was like still in her bed. She was totally dead asleep. The dog was not up and walking around. I think he was asleep in her bed at that point too.

8:07And like, this did not sound like dog nails. So we were like, that is super bizarre and weird, but you know, whatever. Apparently we just hear footsteps in our house now. So we go back downstairs and we start up the show again and like almost immediately start to hear the footsteps again. And we're like, oh my God, it is not somebody walking around our house upstairs. It was the fucking show. Yeah. But I was texting Paige this whole time because I was like,

8:38oh my God, Paige, we're hearing footsteps. No one is walking around. Alice is asleep. Like this is so creepy. And then we realized that, yeah, the subwoofer for the sound system is like right behind the couch. And I'm, I'm so positive that they did this on purpose in the show that they added sort of like random bass beats that like sort of just sound like footsteps or whatever. Like they're coming for us, they were coming from right behind us. So it like sounded like someone was walking around,

9:08but yeah, we got fooled. I thought there was a ghost in my house, but it was just the alien earth soundtrack.

9:17But now I feel like, so I've told this story a few times of like while we were finishing up the book thinking that I heard Alice's footsteps on our wood floor when I was upstairs, but we also have a subwoofer for that sound system upstairs. So now I'm like, was, I can't remember if I was watching something during that, like when that happened, if I had something on the TV, but like, I'm wondering if it was just the subwoofer or something making a similar noise from like some other show. Yeah. I was going to say, I would swear that you have told this exact story. Yeah. On the podcast before.

9:48Yeah. No, I have to like, yeah, like I've, we've heard these footsteps before and like looked around and saw nothing and been totally creeped out about it. And like, I'm now suspicious that it's just been the subwoofer the whole time. Anyway, I might just be an idiot. It's fine. So, you know, it was, it was exciting. It was like a little extra spooky time from that show. Okay. That's enough of that. So we, like we said, are going to talk about serial killers and specifically the science of serial

10:21killers. And what I'll say is that over the years, I've come across very, I'm sure you have as well. I've come across various like pop science articles and podcast episodes about the possible science behind why people become serial killers. So that's things like neurological or psychological factors, environmental factors that might be at play. And even like the weird studies that are like, Oh, people who, well, the one that I see come up all the time is like,

10:53Oh, people who really like gin are like more likely to be sociopaths or something like that. Yeah. I love that one. And I have no, I've never looked closely enough at that to see if there's like any truth to that or if it's just like some weird, I don't know, like misinterpreted thing. Yeah. That people, yeah. But long story short, I'm sure that's more of like a correlation is not causation situation. I just assumed it was some sort of like clickbaity thing. Yeah. Well, yeah, it's definitely clickbaity. Like I, yeah. But anyway, we see a lot of those things.

11:24So, yeah. So we want to take a look at, you know, what's actually going on here with serial killers and what science has to say about why people decide to kill a lot of people. It's going to get heavy. Okay. So today, because this is a broad topic today, we are going to focus specifically on the neuroscience aspect of this. And then the plan is that someday we'll come back to like genetic and environmental factors. But long story short, like all of these things are sort of tied together in one way or another.

11:57So there will be links throughout. And like, we'll come back to this point many, many times, but like not any one of these things makes a serial killer. Exactly. And you know, that's a good point to bring up right now that at a time when people are trying to find like scapegoats for certain, neurological conditions or other health related things. It's never just the one single factor that you can like nail down to like, this is exactly what's happening. It's always more complicated than that.

12:29Okay. So first page, you're going to tell us about what makes a serial killer and some statistics about them. Yeah. So the FBI, their national center for the analysis of violent crime, held a serial murder symposium in 2005 that defined serial murder as the unlawful killing of two or more victims in separate events. A serial killer or serial murderer is then somebody who commits that serial

13:02murder over an extended period of time with lapse between crimes. So throughout that document and others that I've read, they differentiate between what a serial killing and what a mass murder or mass killing is. Okay. Sure. The thing that really differentiates the two is that serial killings happen over that extended period of time, a month or more, and there's a lapse or there's that time between crimes. So it's not like boom, boom, boom, one right after the another, another. And there is no one identified motive for serial killings,

13:35but serial killings do have some common characteristics that suggest the reasonable possibility that the crimes were committed by the same actor. And so they have some sort of pattern that leads the law enforcement or us to believe that it is one or two people committing the crime versus, you know, a bunch of different people doing it. And while serial killings are not new, the term serial killer is pretty new. It wasn't really cemented at least in U.S. law enforcement's vocabulary until the 1970s.

14:09And it seems like it maybe was even later in other countries. So like it's not the first time that the word serial killer or serial murderer was used, but it's the first time where it's really introduced into like law enforcement and how they describe a killer. And I just thought this was sort of an interesting topic for us. You already mentioned that like from a scientific perspective, it's interesting, but I also think it's interesting because there are a number of supernatural ties to serial killings. And just like two examples I can think of right off the bat is,

14:41it's werewolves and is it, it's Peter Stube, right? Yeah, it's Stuba, but like you also see it as, as Stump or Stump or whatever. So yeah, there's like eight different variations of his name, depending on what translation you're looking at. Okay. And I think we've talked about that story in the past. And it's in the book. And it's in the book. So if you don't know what it is, go read the book. Or listen to the werewolves episode. Or listen to the werewolves episode.

15:12And then there's one like Jack the Ripper, who's, you know, got like supposed ties to black magic. There's all kinds of different ties to the supernatural world and serial killings. Or just people like going to the supernatural as an explanation for why there's like all of a sudden this increase in killings or deaths. So I thought that was interesting. Yeah. Long story short, before people had like neuroscience to explain why people did terrible things like become serial murderers, they were like,

15:43well, there's like something witchcrafty going on with this person instead. Yeah. Because they just couldn't believe that a normal person would do these things. So, you know. Yay.

15:56So like I mentioned earlier, you'll hear us come back to this point several times throughout the episode, but it's important to remember that there is not just one generic profile for a serial killer. That said though, there have been certain traits that have been identified as being sort of like shared between multiple serial killings. And those include things like having lack of empathy, lack of remorse or guilt, impulsivity, the need for control,

16:28sensation seeking, and things like that. Sort of, I think a lot of the same traits you would think of if you were thinking of a serial killer. Yeah. Yeah. And very few serial killers are actually diagnosed with mental illness. Instead, they tend to display psychopathic or sociopathic tendencies. They may have antisocial personality disorder, but not all are psychopaths or sociopaths. And again,

16:58not all psychopaths are serial killers. And then statistics. And I kind of wish I hadn't put the numbers in here because... You don't want to know. Well, I didn't want to know, but also like I was curious like what you thought. Oh, like what I thought, how many there are. Yeah. Oh, yeah. I honestly have no idea, but the numbers that I'm seeing here are like way more than I ever would have thought. Same. So, I sort of assumed that like,

17:31I don't know, people talk about serial killers like they're everywhere, but I sort of just assumed there were like five at any given time. You know? Yeah. I was wrong. So, Radford University and Florida Gulf Coast University release an annual serial killer statistics report. And I couldn't find the 2024 report. Admittedly, I didn't look super hard for it, but I did find the 2023 report pretty quickly. We're still recent. It's possible that the 2024 is not out yet.

18:01Isn't even out yet. Yeah. Because it would take a long time. Like we're only 2025. It takes a long time to sort through big data sets. Right. So like it's possible it's not there. And I wasn't going to spend a bunch of time when I found the 2023 one.

18:14And here's the other thing is like so many of these, like this was updated in 2023, but like a lot of that data was still like from at the latest 2020, 2021. So. As of 2020, the U.S. alone had 3,613 known serial killers, which is 64% of the world's documented serial killers. Now, that sounds really bad for us. And like, maybe it is,

18:45but also there's some reason to believe that like, that's because we have a more established law enforcement than a lot of countries. Uh-huh. And maybe like just do a better job of documenting it. So it doesn't necessarily mean we're like 64% hurts, but we're probably not actually that high. Yeah. In the U.S. Yeah. And so the 3,613, that's not like all time that have been identified. Cause I'm trying to look at like the numbers in this like definition of a

19:17serial killer by year. And I feel like that does not add up to 3,000. 3,000. That's because this isn't the entire data set. Oh, okay. So the data set goes all the way back to the 1920s. So they basically, I think like went back and, and identified and documented, like they went back and like found serial killers that weren't yet called serial killers and brought them into the data set. Okay. But that's not like who's active right now. That's just like all of them. All time doc.

19:48Yeah. These are just like every documented case. Okay. It's been 3,613 in the U.S. Yeah. Which I mean, in that case, if they're going back like a hundred years, I mean, it's still not great. Still pretty high.

20:03Yeah. I mean, it's still upsetting. Like I'm looking at this chart that you have in here that says number of U.S. serial killers active each year. Yeah. And. And that's just the U.S. Yeah. And if you go like three or more victims. Yeah. There's like 11 as of 2021. So that's 11 in a year. But like, it's also really interesting that the numbers. So like back in 1998. Sorry, if you're going to talk about this, I'm just. No, that's fine. There's two definitions here.

20:34It's either two or more victims or three or more victims. So I assume like, you know, just depends on how people look at it. But the numbers are higher. Like if it was three or more victims, they say 90 active serial killers in 1998. And then like it pretty much like the trend is that it goes down every single year through 2021, which is where it ends, which I assume is just like because genetic testing has gotten so much better. Right. So they actually talk about this and I don't remember if they talk about it specifically in that report or if it's talked about.

21:06University of Michigan did like a summary of the report. I don't remember which of those two they talked about it, but they believe that part of the reason for the downward trend. Is the improvement in technology and like things like social media because it's harder and like improvements in law enforcement because it's harder for people to get away with things. Yeah, exactly. For longer. Yeah. And like specifically they mentioned that like it, it's become a lot more difficult to commit those types of repetitive crimes for motives that

21:42were more for like financial gain and fraud. So like it's just easier, I think, to pin down or track. I'm sure genetic testing is probably a part of it. Well, I just mean like genetic testing in like or like DNA testing in like they like somebody kills. Oh, that's what you meant. Yeah. Like somebody kills one person and they find DNA evidence like more often because they have more ways of getting it and their tests are more sensitive.

22:12So like they're more likely to catch them on the first victim rather than. Yeah, more quickly. Yeah. Yeah. Yeah. I'm sure that's part of it too. So yeah, just like basically I think it's that people just can't get away with it as easily anymore. Yeah. Suck it. So I'm going to say something that's going to be like very depressing is that I would be curious to see this table next to a table showing the number of mass murders a year because I would guess that that number has gone up significantly since 98.

22:44Yeah, probably. Which is the worst, but we're doing anyway. I did. I did say this was not going to be good.

22:57It's very interesting. Like all the statistics and like, yeah, it's all very interesting, but it's all like, oh no. Yeah. Yeah. Yeah. I'm not going to. That's all I'm going to say about that. So yeah, go ahead. That's it. That's all I got. Okay. So, so yeah, there's been thousands of serial killers in this country. So that's great. So why do they do it? That's the big question. And like I said, we're going to focus on the neurological or psychological aspects of it in this episode,

23:29but future hoping we'll get into like environmental and genetic factors because they exist as well. Okay. So researchers have been studying how differences in people's brains can affect their behavior for a long time. And this includes many decades of study trying to understand why people commit violent acts. And Tyson and I talked about the tamping rod like blown through his frontal lobe and like his behavior changed.

24:14And it was like a big step for neuroscience as like a scientific field to understand like what happens, what is controlled in different parts of your brain. And to that point, speaking of Phineas Gage, things like brain injuries and mental illnesses like bipolar disorder or schizophrenia can play a role in people committing violent crimes. But as we mentioned before, mental illness is actually present in only like a few serial killers.

24:46And yeah, and it's just like those types of disorders are not necessarily linked to violent behavior. So it's sort of like a dangerous tie to make. So I just want to be really clear about that. Okay. So long story short, we've known for a while that there are certain parts of our brains and other neurological factors that can be associated with violent and specifically homicidal behaviors. And these differences fall into three main categories.

25:21And they are functional differences, which means that certain parts of the killer's brain are more or less active. Or there are differences in like the amount of communication that happens between different parts of their brains. There can be neurochemical imbalances. So this is that they have abnormal levels of key neurotransmitters like serotonin or dopamine. The third difference is that there can be structural differences,

25:53meaning that like physically there are larger or smaller portions of certain parts of the brain that control like key functions related to, you know, why people might act in a violent way. So we're going to talk about some specific research examples or each of these differences that can happen between normal and abnormal brains. But this is a good time for another reminder to kind of like we're going to bring this up a lot. But nature versus nurture matters, right?

26:24We can't preemptively condemn people because of the way their brain works or any other like physiological or psychological factor. Like that's obviously a very dangerous path to go down. And again, not all serial killers would even be diagnosed as psychopaths or sociopaths. And some serial killers brains like don't exhibit abnormalities at all. And long story short, there is no one like true serial killer brain.

26:56You couldn't just look at somebody's brain and be like, yep, that person has killed people. Yeah. So correlation is not always causation. And if you look through these studies, there are, you know, entire papers dedicated to the ethics of even considering these types of differences because you don't want to go down that role of accusing people or like saying that people are going to commit a crime like that just because of some physiological or neurological thing they've got going on. Yeah. Well, and I think like every single paper I read

27:28ended with something like, again, this is like just a predisposition or this has to be present with all these other factors before it's even. Yeah.

27:47So, yeah. So honestly, the first example that we are going to talk about is sort of like the perfect example of that point. So I'm going to start with functional differences. So again, this is where certain parts of the brain are more or less active in people who become serial killers or are serial killers because they have to take known serial killers or murderers and study their brains after the fact. So in the late 20th and 21st centuries,

28:19there have been a lot of studies, basically since we've had, you know, the technology to scan people's brains in detail. But we've had a lot of studies that have focused on using scans and imaging of brains of known murderers and serial killers to understand how their brains might be different. And obviously, you know, this is how we're going to narrow down things much more specifically than like has been done in the past where it's sort of just, you know, general like, oh, this region of this person's brain got damaged, like, and it made them weird. So in a particularly famous example,

28:51looking at differences in brain function, one researcher accidentally discovered that he was a psychopath. And this story was featured in like this, what I would consider a classic criminal podcast episode that I can remember listening to when I was first like really getting into podcasts and thinking like, man, this doesn't even sound real, but it is the craziest story. Yeah. So it's back in 2005 and a neuroscientist at UC Irvine named James Fallon was,

29:24which is funny. Like I was like, not the Jimmy Fallon. Not Jimmy Fallon.

29:29I had to like, honestly, I'm going to double check it right now. Cause I was like, did I write that wrong? Nope. It's James Fallon. He's that's, that's him. Okay. Anyway, so he was using PET scans of the brains of psychopaths, including serial killers, trying to determine anatomical patterns associated with psychopathic tendencies. And honestly, I just took this opportunity to find out what a PET scan is.

30:01Cause I don't think I've ever known. So you guys get to know about it now. Yeah. But a PET scan is a positron emission tomography scan that uses a radioactive tracer that gets injected into the bloodstream. Or I guess sometimes people will like breathe it in, in a gaseous form. But this tracer, as it gets like taken up by the body, people are able to image how organs are working in real time, like including people's brains.

30:32And positrons, in case you're wondering, are positively charged particles ejected from the nucleus of an unstable or radioactive atom. They're basically the opposite of an electron. They're a little positively charged particle rather than a negatively charged particle. And for the brain, a PET scan will show the active areas. So like as, you know, those parts of the brain become active, then it'll light up on the scan. And areas that are more or less active will be brighter or darker in the image,

31:06respectively. In the case of like a brain tumor, it would show up really bright on the scan because the cancer cells are more active and take up more glucose, which is what the radioactive tracer is dissolved in. So I thought that was really interesting. And when it comes to people with neurodivergent brains or functional differences in their brains, the scan would be able to see if certain areas were more or less active than in a neurotypical brain

31:36or like a pathologically normal brain. And what Fallon was noticing was that psychopathic brains showed low activity in key areas of the frontal and temporal lobes that deal with empathy and morality and self-control. And more specifically, areas that show abnormal activity that have been found in this and other studies are the parts of the brain associated with the frontolimbic system,

32:07including the hippocampus, prefrontal cortex, and amygdala, which in addition to affecting things like empathy, morality, and self-control, also play into emotional regulation, impulsivity, social cognitions, like whether or not you can understand social cues from people around you, and memory. So like, you know, all the big things that they say that someone who is a serial killer, and in particular a serial killer who would be designated like as also a psychopath or sociopath,

32:42things that they struggle with. So one fateful day, 2005, coming back to Fallon, he's looking at these scans that are sitting on his desk, and he just happened to have scans of his and his family's brains out as well, for a different study that he was working on at the time. And he noticed that in one of these family scans, one of the brains showed clear signs of psychopathy. And the image had been de-identified,

33:12so he didn't know which family member it belonged to, and like that's pretty standard in medical studies, because like you don't want the researcher to be biased, and like especially if he's dealing with images of his own family's brains, you don't want him to know exactly who it is, or else it might affect his interpretation. But for this case, he was like, well, shit, like someone in my family is a psychopath based on this brain scan. So he decided to check to see whose brain it was,

33:42and like break the blinding that was in place. And turns out it was his own brain. I love this story. I know, it's such a good story. And like obviously Fallon is not a serious violent criminal. He's a neuroscientist who's like studying why people act violently. He is obviously kind of rattled by this, and he went on to check to make sure there wasn't an issue with the PET scan machine that he was using.

34:15Like, did it just, you know, have a false positive for him? He did some follow-up testing on himself, both genetic testing, but also found out that he had, I think it was like seven other murderers in his family line, including Lizzie Borden. But anyway, he does this follow-up testing, does this follow-up research, and ultimately concludes, okay, well, this is what my brain says, and this is the corroborating evidence that I have. Like, I am a psychopath, I guess.

34:46But he would be what's considered a pro-social psychopath. So someone who has trouble feeling empathy for others, but like still behaves in socially acceptable ways. So, like, it's lucky for everybody else. And also, like, is that the worst thing? Like, don't you sometimes wish you felt less empathy for people?

35:15Lately, life might be easier.

35:21To that point, what I was going to say, and this is sort of like my own interpretation, but like, I do sort of think that the tendencies that, you know, the lack of empathy and sort of that kind of stuff, like, that might make somebody else a killer, like, could be part of what makes him a good scientist. Like, he's probably more able to remain objective and stuff because he's less affected by, like, emotional ties to his subjects or his work. And I guess he himself said, like, once he started thinking about this,

35:55he is quoted as saying he is obnoxiously competitive and, like, would consider himself to be aggressive, but not in, like, a physically violent way, but, like, in a, like, I need to win an argument kind of way. But, like I mentioned before, he's also sort of the perfect example of nature versus nurture because, like, he grew up in this very loving family. His parents were very involved and supportive of him. And so, like, he obviously did not become a serial killer.

36:27But anyway, their brains can be different, which is fascinating. Yeah, I love that story so much. Yeah, it's a great one. So that brings us to the second type of difference, which is neurochemical imbalances. So, Paige, you can tell us about that. So I specifically focused on serotonin and dopamine, which I think you mentioned upstairs. You mentioned it upstairs. Yeah, upstairs. Earlier.

36:56Mostly because there has long been a relationship between low levels of serotonin and dopamine and impulsivity and aggression. So I don't have, like, Megan, you had, like, a specific story about somebody who is a psychopath, but mine is more focused around how serotonin and dopamine can cause people to have impulsive behaviors or aggressive behaviors. And serotonin and dopamine are known by most as the feel-good chemicals.

37:30And both are neurotransmitters, and they play important roles in things like mood and emotion regulation and sleep. So important things. And I said I focused on both of them, but to be honest, I really kind of just focused on serotonin. But that's okay. That's fine. I lied. They kind of interact with each other, right? Yeah, yeah, they do. So serotonin specifically is more for mood and sleep regulation, and dopamine plays a crucial role in the reward system in our brain.

38:01So things that drive, like, our motivation and desires. I did learn through this that apparently 90% of your serotonin is produced in your intestines. Which, like, am I just an idiot for not knowing that?

38:15Is that, like, a thing that everybody knows? No. But, yeah, there's been, like, a lot of studies that have been done recently looking at ties between, like, people's gut microbiome and whether or not they suffer from, like, neurological conditions. So, like, because that's where serotonin is. Yeah, and I guess, like, I knew that, but I guess, yeah, I guess I just didn't know, like, why. Like, I had seen that before, but I don't know that I've, like, actually read why that was the case. So, oh, I don't know.

38:45It's also why, like, if you, like, start, like, an antidepressant or, like, an SSRI or whatever, a lot of people experience upset stomachs and stuff because, you know, that's where the magic happens normally. So. Huh. Well. There you go. Now I know.

39:03Anyways, I didn't know that, like, 90% of it wasn't even produced in the central nervous system. That really blew my mind. Yeah. It's crazy. So, yes, serotonin makes you feel good and has been linked to these, like, impulsive and aggressive behaviors. And a study published in Biological Psychiatry, which apparently is a word I can't say, in 2011 by Dr. Molly Crockett and Dr. Luca Passamonte

39:33at University of Cambridge, they studied this exact thing. So they were looking to see how a decrease in serotonin would affect how people respond to feelings of anger. So, like, if it makes them more aggressive or makes them angrier or are they able to control those feelings. And so, what they did is they basically manipulated the participants' diets. On test day, participants were given a mixture of amino acids

40:04that lacked tryptophan, which is the building block for serotonin. And then on placebo day, they were given the exact same diet, only that one had the normal amount of tryptophan. And they would give them the diet and then use functional magnetic resonance imaging or fMRIs to scan the participants' brains while looking at images of angry faces compared to a neutral or a sad face. And, which is like,

40:35reading it at first, I was like, I don't understand. And so what they did is they would look at what different parts of the brain lit up and how they would communicate with each other. And they were specifically looking at the amygdala, which is where those feelings of anger are generated, and then the prefrontal cortex, which is where responses to those feelings are controlled. And they also gave a questionnaire to all the participants at the beginning to identify

41:06which individuals had like a natural tendency to behave aggressively. And then after the serotonin depletion, they looked at the results from the fMRIs. And they found that not only did the lower serotonin levels make for like a weaker communication between the prefrontal cortex and the amygdala, meaning that like you have the feelings