Mass shootings, bullying and retaliation, and other acts of violence — why did the human brain evolve to be so aggressive? Dr. Heather Berlin, assistant professor of psychiatry at the Icahn School of Medicine, talks about the genetics of violence, the “mean girl” phenomenon, and why some psychopaths end up in jail while others land in the corner office.
Dr. Stieg: It seems like every time we turn on the TV or go to our computer or onto our cell phone, we learn about another terrible act of public violence to help us better understand what’s happening in society and in the brains of individuals committing these crimes. I’ve invited Heather Berlin, an assistant professor of psychiatry at the Icahn School of Medicine at Mount Sinai to delve into this subject more deeply. Heather, thank you so much for joining me. One of the most worrisome things is it seemed like violent crime was actually on a downtick. Now all of a sudden it seems to be on an uptick. Why is it that this violent crime is on an uptick?
Dr. Berlin: I think that aggression and violence is adaptive for survival. We’ve evolved to be aggressive and really it’s less natural to override our aggressive impulses. It takes cognitive energy. And so when people are agitated, whether it’s because of poor economic situation, because of social isolation, and we see this in other animals as well, they tend to act out aggressively. If you take people or other animals again and put them under significant amount of stress, they are much more likely to act out aggressively. It’s an instinct. Now, if you add weapons to that guns, you know, and that people can now go and grab a gun and when they have that impulse to be violent ends up shooting tens or even hundreds of people. That’s where these big problems come in.
Dr. Stieg: But are they acts of violence or are they acts of rage? Are they manifestations of the social environment? I mean, what’s really going on?
Dr. Berlin: Well, there are a number of different reasons why people act up. Some of them are impulsive aggression. So you have this overwhelming emotion and you just act on it. You’re not able to say suppress it. And there’s a number of neuro-biological explanations for that, which we could talk about. But in other cases, people, it’s more methodical. It’s actually very, they’re very cognizant of what they’re doing. They’re planning ahead and these are the differences that you get into in terms of punishment between like first degree and second degree murder, so there’s just acts of, when it’s passionate and you walk in and your spouse is in bed with someone else and you shoot them and that’s a crime, but you’ll have less of a charge than if you had planned for weeks or months in advance to to kill the person she’s having an affair with.
Dr. Stieg: There’s a little bit of an implicit bias in the way you’re answering these questions and I just wanted to challenge you on this, in that there is aggressive behavior —understanding what we know about the development of the human brain. The male brain has a more dominant amygdala, which is the anxiety and anger manifestation portion of the brain. Whereas the female brain is more frontal lobe cognitive, rational, more thinking and memory. Is there this fundamental boy, girl, male, female, gender difference in violence?
Dr. Berlin: On average, we see that, I think in humans, it’s like 90% of violent crimes are committed by men, and in chimps it’s like 95%. But this does not mean that women are not aggressive. But they can, it can manifest behaviorally in different ways. So whereas men you have this interaction with testosterone, which we know is linked to aggressive acts, tend to be violent towards other people. They end up going to jail. Whereas women, and this is all on average, obviously there are exceptions to these roles, but they tend to be more inwardly directed, introverted and they can be aggressive to themselves. Like we see things like self-harming as much more prevalent in women and they tend to get then diagnosed with something like borderline personality disorder. But what I see is, what’s interesting is, and something that I found is that a certain part of the prefrontal cortex, the orbital prefrontal cortex is involved in impulsive and aggressive behavior. So when you have either too little activation in that part of the brain or differences, structural differences, you tend to be more impulsive and aggressive, but men tend to act out on others and they’ll get diagnosed as antisocia personality disorder. Women tend to be aggressive towards themselves, self-harming and they’ll get diagnosed as borderline personality disorder. But it’s the same underlying neurobiological problem just interacting with male versus female traits and manifesting itself in different ways.
Dr. Stieg: There is a fair amount of data though coming out both on the neurobiology and also the genetics part of this. Yes, gender is important, but in terms of the neurobiology, there are things that occur in the male brain; there are deletions from chromosomes. Can we go into that a little bit?
Dr. Berlin: Yeah, so well there’s been a number of genetic components that have been linked to aggression but but one in particular, which is on the X chromosome where you see a deletion that would relate to something called monoamine oxidase, which is a precursor to serotonin.
Dr. Stieg: And serotonin is a neurotransmitter that’s responsible for making us… happy.
Dr. Berlin: Happy in general, yeah. And other things.
Dr. Stieg: So it means if you have, if you lose this enzyme, you don’t have enough serotonin, you’re not happy.
Dr. Berlin: Exactly. And you tend to be more aggressive also more impulsive. It was also interesting, sort of a side note, is that when people, there’s been studies which look at people in the throes of passionate love in the early stages of love and they actually have decreased serotonin, which related to obsessional thinking, you’re obsessed with the person and also more aggressive behavior, which makes sense because you need to fight off competitors. So you can see it, you know, even in people without the deletion, but that lower serotonin levels are linked to more aggressive behavior overall.
Dr. Stieg: I want to get back into the motive behind this. Is there anything scientific we can say is, you know, the murders that were committed in Columbine versus the temple in Pittsburgh and, more recently, the shopping mall in Texas, I guess, somebody drove in with a van. What’s the, what’s the differences or what’s the similarities?
Dr. Berlin: Well, it’s hard to generalize, right? I think there could be different underlying causes for each particular crime. We do know that there have been studies which look at incarcerated murderers and they find that they have significantly less gray matter in parts of their prefrontal cortex.
Dr. Stieg: So the brain is lighter, less mass.
Dr. Berlin: Yeah. Particularly the brake system of the brain is not as heavy, let’s say, or it’s not. The other aspect is that it’s not connected as well to the amygdala. So you have the amygdala, which is kind of like related to that fight or flight response and the aggressive responding. We see that people who are aggressive have more activation in the amygdala. And then you have the prefrontal cortex, which kind of modulates that amygdala response. So in people who have less matter or gray matter in the prefrontal cortex or the connection between the, I’m going to say orbital prefrontal cortex and the amygdala is they have sort of either damaged connection or the connection isn’t as robust as in sort of what we’d call a healthy or normal control, then they tend to be more aggressive. They can’t control these sort of basal instincts.
Dr. Stieg: The reason that we’re talking about this orbital prefrontal cortex is basically the part of the brain that sits directly above your eyes, right behind your forehead.
Dr. Berlin: Yeah.
Dr. Stieg: And those are the areas that can either be underdeveloped or as a result of multiple traumas, say from multiple concussions or boxing. This is the area of the brain that is injured.
Dr. Stieg: We talked a little bit about genes, but is violent behavior genetic? You know, if my dad was a mass murder or am I going to be a mass murderer?
Dr. Berlin: Well, it’s not a one-to-one correspondence, but we do see that there is some heritability. So there is a genetic component, but that basically gives you a predisposition towards being aggressive, but then it interacts with your environment. So we call it the stress diathesis model, which means that you have a sort of vulnerability or a predisposition that, if that interacts with a very stressful environment, then you’re more likely to manifest that sort of genetic predisposition.
Dr. Stieg: And we’re all aware of the changes that go on during the development of the teenage brain. What role does parenting play during that time period for helping to develop an overly aggressive male or female?
Dr. Berlin: So against what our sort of inclination is and my inclination as a parent, the research actually suggest that the influence of the parent is not, it’s not that much that they’ve looked at. The peers matters more. And really your genetics play a large role in terms of let’s say your personality. So they find that something like antisocial personality disorder is there from early on you can recognize it. And when it’s a child it’s called conduct disorder. It’s those kids that are, you know, harming animals or bullying and sort of lack empathy. And you know, whether you’re a really great parents or not, if there’s a certain genetic predisposition that is gonna make you sort of behave in a certain way throughout the course of your life. So the upbringing can like, push you in a little bit, one direction or another. But some of these personality disorders are just lifelong.
Dr. Stieg: What about, let me give you the example of the abusive parent or the stressful parent in a, you know, in a child doesn’t or couldn’t that have impact on the child’s stress levels, which means that their cortisol levels, the stress hormone might be up — that’s going to have impact on the things we were talking about. The dopamine levels, they’re not high so they’re not happy. The serotonin levels are low. So they’re…
Dr. Berlin: Mmhm. Studies do show that during these critical periods of brain development, like if you’re exposed to stress early in life, the cortisol actually affects, for example, hippocampal development. And so we find that people who are older who have disorders like something like dissociative identity disorder, which is a disorder. It used to be called multiple personality disorder. And when we find that they have smaller hippocampi and smaller amygdali, but they usually were exposed to early life stressors. So the stressor can not only affect, how certain genetic predispositions kind of manifest themselves behaviorally. They can also actually affect the brain development itself.
Dr. Stieg: I can’t fathom that during that developmental phase in a child’s life, if you have a parent that is overly aggressive, abusive, not constructive in terms of normal development, that that’s not going to have an impact on the way that child, male or female envisions the world or interacts with.
Dr. Berlin: Yes. But I think it’s hard to disentangle. So, usually if the parent is significantly aggressive and abusive, there tends to be a genetic component as well. So now you’re mixing the genetic predisposition with the sort of modeling behavior of the parent and a stressful situation. So not good all around. However, I do think that there are genetic and neuroprotective mechanisms that if maybe you did not inherit a genetic predisposition and you have a parent who is abusive, it’s not going to be a good childhood for you, but it doesn’t mean that you are doomed to now sort of repeat the mistakes of your parents.
Dr. Stieg: Are there ways that we can look at this? Can we do functional MRI studies, PET scans or something and flash something violent and look at what happens to the brain? And, if so, is it different between me who is kind of a docile teddy bear versus somebody else who’s got a violent behavior pattern?
Dr. Berlin: Yes, yes. So we do see differences and we also see differences just within the course of a person’s life. So when you look at, for example, murder rates, you get a spike just around the age of 13 in men of a violent crime. And that’s a very clear association with puberty and testosterone levels. And then you can see it gradually kind of, it’s like a slope that goes down. We call it the minivan, like a hill that goes down as you, once you have children and testosterone levels go down, you see much less aggressive behavior. Now we can also look in people’s brains and see that for example, people who are sociopaths or have antisocial personality disorder have a few problems. One is they could have increased amygdala activation to stressful stimuli or fearful stimuli that’s presented to them. They have less prefrontal cortex activation so they can inhibit that aggressive impulse. And they also, there’s an empathy network in the brain. So when we show people certain pictures that are meant to elicit empathy, like somebody getting hurt or a baby is crying helplessly, we see a certain pathway and involves parts of the brain, like the anterior cingulate and the insula. But in people who don’t experience that type of empathy, who are more likely to act out aggressively, we don’t see the same activation in that network.
Dr. Stieg: Want to flip away, a little bit from the massive violent crime and deal more specifically with self-harm that women will commit against themselves. What’s the basis for that?
Dr. Berlin: There are a couple of things. One is that usually they’re having some internal strife or some emotional dysregulation, and in a way it seems counter intuitive, but it’s, it’s a way to relieve pain, their own internal emotional pain. So if you kind of like do something very sharp and painful, actually it hurts at first, it kind of takes you away from your emotional pain. But then when your body releases endorphins actually after you’ve gotten, you’ve had a cut, let’s say, and it could actually feel good after. So in a way it’s to sort of relieve their own internal emotional pain by self-harming. And another way that women are aggressive, not just themselves but to others is they do it in more covert ways. So they’re aggressive. Women might not go and, and, and punch someone or beat someone up at school, but they can manipulate people for their own gain. It’s kind of the mean girl at school who doesn’t care about hurting other people’s feelings so she can get an advantage and become more popular. So there are ways that women can be aggressive. It’s just as aggressive as men, but just in, in different ways.
Dr. Stieg: That’s common during the teen years that so often just gets overlooked as a manifestation of that time period in life. And we watch it and hope that they grow out of it. Correct. And the majority of people do.
Dr. Berlin: Right, but not all. And there’s actually been a recent study which shows that actually in men who are what they call successful psychopaths. So there are the ones who don’t commit crimes but they end up as CEOs on Wall Street because they were able to kind of not worry about who they were hurting along the way. And they find that they have similar aggressive instincts. However they have actually, they had more gray matter in their prefrontal cortex compared to their non-successful sort of psychopaths who ended up in jail. So they had some, a bit more ability to modulate those aggressive impulses, still being manipulative and still having a lack of empathy. So they’ll do what they can for self gain, but they’re doing it in a way where they actually achieve success rather than ending up in jail.
Dr. Stieg: There’s been a lot of news lately about average behavior by certain individuals outside of violence. Do you envision a day where people are going to get off by virtue of the fact that they’re going to have a genetic test? It’s going to say, “Gosh, I had no control over it. It was in my gene pool.”
Dr. Berlin: It’s an interesting sort of ethical question. They’re already allowing brain scans to be submitted in courts as evidence. If you take someone who’s done some horrible crime, let’s say a mass murderer, you don’t have to show me a picture of their brain for me to know that there’s something abnormal there and that they need to be removed from society so that they don’t harm other people. And if we get really sort of a little bit into the weeds, but more philosophically speaking, we don’t really have free will so to speak. I mean we are really, we are our brains and what we do is determined by how our brains function. But I think that we can hold people responsible for their actions to the extent that they have the capacity to have self control. So if they have a huge lesion in their prefrontal cortex, they just have no ability to control themselves. We hold them less responsible. If they have a genetic predisposition towards violence, however they were able to hold down a job and perfectly well controlled their sort of aggressive instincts and other circumstances and then they just go murder someone. We hold them more responsible.
Dr. Stieg: I understand that there’s some new animal studies and human studies looking at children that grow up in an aggressive environment and the impact that that can have not only on their aggressive behavior but also on their overall health such as depression and immune complex diseases and things like that. Can you give us some insight on those studies?
Dr. Berlin: if you take a healthy adult person with no sort of genetic problems and you have them just simply imagine an aggressive scenario versus imagining a neutral scenario. Imagining aggression actually decreases prefrontal cortex activation in the brain. So theoretically you could go out and become more aggressive just by like, let’s say, watching something aggressive. So if you scale that down to children whose brains are still developing and they’re observing aggressive behavior, they might either develop sort of helplessness and hopelessness, which can lead down a path of depression or they might, you know, sort of mimic that behavior and become abusive themselves. But we also, again, I want to, you know, as with anything, it’s very difficult to disentangle the genetic and the learned. But there are some studies which look at morality in, in very young infants as young as like 18 months, six months. Um, the studies were done by Karen Wynn at Yale, and she basically would show these infants a bad puppet that was stealing something from another puppet or a good puppet that was helping another puppet. And then she would just ask them to choose which one they wanted, the good one or the bad one. And the majority of the time they would choose the good puppet. Right? So they were making these moral decisions very early on. But there was that handful of kids that were choosing the bad puppet, right? So it’d be interesting to kind of follow them up through life and see are those the ones that go on to develop conduct disorder and become sociopaths. And you know, at that point it’s like, I don’t know, no matter how much good parenting you throw into the mix, that it’s really going to change fundamentally who they are.
Dr. Stieg: Do you think that compassion and empathy can be taught or if you’re not empathic, you’re never going to be empathic?
Dr. Berlin: For example, like with biases, right? Implicit biases. So, to get people to wear virtual reality glasses and see, for example, um, take a Caucasian person and see what it would feel like for them if they were an African American and how they’re being treated and sort of to get them to be able to walk in someone else’s shoes, to maybe increase their empathy or their understanding. So I think there is some flexibility there, but when you take the extreme cases of people that really just have — when they see an image which you really should feel something and they don’t get any amygdala activation… it’s going to be very hard to train them to feel something. But I think that, the average person, you can enhance their empathy.
Dr. Stieg: And is that at all related to educational level, religious background? I mean it seems to be that there are so many variables when we start talking about the neuropsychology of behavior, that it’s, it’s really hard to say if I change that I’m going to fix everything.
Dr. Berlin: Yes. Well there’s so many factors that it’s hard to pinpoint, but I can say that I don’t think that, for example, like people who are the more or more highly religious or devout are necessarily the most moral,
Dr. Stieg: if there was an easy answer, we would probably have it by now. Do you have any suggestions? Everybody has to go through school. Yeah. Are there things that we could do in the elementary and middle level schools that would help us identify some of the individuals that might have overly aggressive behaviors that we can help them before this craziness happened?
Dr. Berlin: Yeah, I mean I think one of the biggest problems with a lot of these, these recent crimes, I mean starting from Columbine on is to do with social isolation. So I think when a lot of these kids feel like they don’t have any prospects to integrate socially or, or any chance, let’s say with the opposite sex, this is their way of either acting out of rage or getting attention. This is their only option they feel. So if we can work on the aspect of social isolation by, by, by working on inclusion and acceptance of diversity, people, teachers, you know, adults noticing when there’s somebody who’s the social outcast and figuring out how they can integrate them. Now with the, with the internet and online people are becoming even more and more socially isolated and then they are in these sort of thought bubbles where they can enter hate groups and get really worked up. And so we got to start it early on — the process of breaking that cycle, which I think the key element is, is socialization. So, and we know that, like, if you, there are studies which show that kids who are online more, on screens more, the time that they usually used to spend learning how to sort of pick up on emotional social cues they’re losing. So they, they’re not even understanding how to socialize, but we see that if you take them off the screens they can recover that ability. So I think part of it is getting them off screens, getting them to interact and working that into the school system somehow.
Dr. Stieg: You see that happening in the school systems?
Dr. Berlin: Um, in certain schools, yes. Um, but I don’t see it happening as a matter of policy in public schools.
Dr. Stieg: Yeah, that’s been my great concern is, is the impact that social media is having on isolating people within society. Heather, I want to thank you for opening our eyes and our view on violent crime. You’ve shown that there isn’t really going to be a simple answer, but I couldn’t agree with you more that at the early school levels, we have to start getting our children integrated into society. When we’re employing individuals, one of the major things we look at is emotional IQ, and that has to be as important in our educational process as reading, writing, and arithmetic. And unfortunately, I think that that’s been a little bit overlooked in the past decades. Thank you so much for being with us.
Dr. Berlin: Thank you so much.