"Oh, my brain scan shows I am a psychopath. How very useful!"
While I do believe neuroscientists mostly know less than often implied, the research is very interesting.
He describes himself to be competitive, wrangling with his own ego. But wouldn't it be true then to say that he is no psychopath and a brain scan is insufficient for diagnosis?
And what is defined as healthy? Certainly not the absence of competitiveness or ego.
> But when he underwent a series of genetic tests, he got more bad news. “I had all these high-risk alleles for aggression, violence and low empathy,” he says, such as a variant of the MAO-A gene that has been linked with aggressive behavior. Eventually, based on further neurological and behavioral research into psychopathy, he decided he was indeed a psychopath—just a relatively good kind, what he and others call a “pro-social psychopath,” someone who has difficulty feeling true empathy for others but still keeps his behavior roughly within socially-acceptable bounds.
> It wasn’t entirely a shock to Fallon, as he’d always been aware that he was someone especially motivated by power and manipulating others, he says. Additionally, his family line included seven alleged murderers, including Lizzie Borden, infamously accused of killing her father and stepmother in 1892."
...
> “I’m obnoxiously competitive. I won’t let my grandchildren win games. I’m kind of an asshole, and I do jerky things that piss people off,” he says. “But while I’m aggressive, but my aggression is sublimated. I’d rather beat someone in an argument than beat them up.”
I read the article, that is why I referenced being competitive for example. But the "quote" wasn't meant to be attributed to him, I just thought it funny. Just wanting to throw in the idea, that maybe he isn't a psychopath, not even in the pathological sense.
One of the defining characteristics of a psychopath is the lack of empathy. That is not to say you cannot learn when to feel empathic, and he touches on that too. Maybe we just need to change our definition, or invent a new one. One can be a pathological psychopath, but not be "a psychopath", because they was loved and cared for properly. Essentially they learned that social connections was overwhelmingly beneficial for them.
Psychopaths can fake empathic behaviours. In fact they're so good at this they can appear unusually friendly and caring.
They do this by modelling social interactions and replaying them. It's more of a scripted response: "In this situation, act as if you feel like this."
I don't think they can learn to have genuine empathic feelings, because the part of the brain that would normally have them doesn't work very well.
It's not something good parenting can fix. It can maybe mitigate it to an extent, but it's not unusual for average-to-good parents to be completely baffled by a son/daughter with serious personality issues that are primarily genetic.
> But wouldn't it be true then to say that he is no psychopath and a brain scan is insufficient for diagnosis?
That question can't be answered without buttoning down the term. Generally diagnostic manuals don't recognise such a condition without actualized anti-social behaviour.
I think that jims aggressive arguments behaviour comes not from its genetics or frontal lobe abnormality. Its come from his past childhood. Being loved so much in childhood make people become a competitive person and egocentric. They get used to be a center of attention and think that arguments, will and other persons needs is irrelevant. They are not violent in physical things but violent in how they treat people.
There were studies that said that people with higher IQ have more self control ability under alcohol influence. I think its the same in this case. Jims ability to control itself come from good education that furthermore increase his self control.
"Being loved so much in childhood make people become a competitive person and egocentric"
No it doesn't, that's a ridiculous generalisation, children are specifically taught to restrain their competitiveness by their role models reactions to it, it's not the amount of love they get, it's the priorities of parents, there are many noncompetitive people who received a lot of love as children.
I wonder how many of those who run for public office would willingly present results of such a scan... I would bet money that that particular demographic would show an interesting trend.
Seriously, gross deformations of the brain, visible to the naked eye, are pretty dubious and questionable in my mind.
Meanwhile, the genetics that produce psychological disposition are more than hotly debated. Why? Because, think very carefully about where this story takes us. If we can say intellect is linked to genes, this puts a huge number of people in a box they cannot escape. Should the "dumb" people reproduce? Do we put laws in place so that only useful people have children?
I don't doubt that there may be a trend, but to me it sounds very unfair to allow people's immutable biological characteristics to enter into an adversarial debate about how they might act.
Also, the mechanics of how macro-scale neurology affects a person's psychology and sociology is still poorly understood, which makes the data especially easy to abuse. More than anything, I think the researcher's findings highlight this point; he was a counterexample to the theory that a diminished prefrontal cortex implies anti-social behaviour, showing the phenomenon to be more nuanced.
I don't doubt that while some "psychopaths" will be detectable ahead of time, and maybe mitigated (whether or not that's ethical), there may be many with "correct" views read as possibly psychopathic that will get strawmanned into oblivion due to their diagnosis.
Because it is prejudicial, which is unfair because it fails to take into account the person's individuality. Such traits do not simply equate to behaviour, the relationship is complex, incomplete and the mechanics not understood. A person's membership of a class which they neither chose to be in, nor can choose to remove themselves from (in this case a genetic brain anomaly), can not infer a fact about their mind or behaviour.
I'm not so sure about politicians but there have been studies that showed that there are more psychopaths as CEOs and people at the top of businesses. Politicians in reality do a lot of soft people work - more so than a business man would - and they are often more motivated by and need empathy for their job.
Psychopaths do have people skills, if only as superficial, learned behavior. And they have excellent intuition, and perhaps even empathy, of a sort (in that they do seem to have a feel for what others might be going for) for zero-sum, win-lose situations, like politicking. This does come at a cost, of course: they lack pro-social emotions and the ordinary empathy that relates to those; hence, they tend to fail at things like creative negotiation, adaptation and compromise (that are critical to success in win-win scenarios), and to also lack traits like intellectual and social curiosity, openness to experience, a sense for human achievement, for culture and the arts, etc. Maybe even a sense of humour! All-in-all, by and large, they are not good policy-makers - they don't exert what Bernard Crick (a widely-quoted political scientist) called the "political virtues".
On a side note: Should he have been able to see whose results he was looking at? It's surely unethical in my book. Even when, or perhaps even more when, working with data from relatives the burden of ethical behavior lies with the researcher. De-anonymising shouldn't be the researchers option without safeguards imho.
Yes, researcher needs to be trained on ethics specifically. It is a part of psychological education, it is a part of APA's mission[1]. Psychology takes it seriously after Little Albert Experiment[2], Ash Conformity Experiment[3], Zimbardo's Standford Prison Experiment[4], Milgram Experiment[5] and a lot of others. Now it couldn't be done, a researcher needs to approve his experimental plan with APA Ethics Committee.
It means, that any competent researcher in a psychology would know ethical risks (due to education), and if he is testing his research plan on his family, he must be ready to find something unexpected, and he must inform participants on the risks.
We are missing the boat with ethics everywhere--I work with people every day that aren't even aware of the unethical actions they are taking in the healthcare realm. It's very easy to avoid ethical behavior if you have never received any training in ethical practices.
Breaking the double-blind restrictions of his study was an ethical breach. He was affecting the outcome by damaging a key instrument in the study (himself). Breaking the rules and being a maverick is sometimes useful, even ethical behavior, but in scientific research, if you go through all the effort to design a study, you should uphold the plan.
As far as all this psychopaths can be detected with a brain scan bs, well, it is just that--bs. I don't think there is an easy test to determine who is going to lead a life of crime and who isn't. I do think a lot of unsavory people rise to leadership roles. That is for certain. It would be nice if we could do something to control those types of people before they take such a huge toll on the rest of us.
What I found most annoying was his propensity for drawing easy conclusions about how his loving upbringing somehow prevented him from being another Lizzie Borden. Again, does this guy have any scientific training? There are tens of thousands of lurking variables unacknowledged there!
After reading that book a couple of years ago I've wondered if psychopaths are a lot more common than previously thought. Am I one myself? I mean, how can you know for sure? We have no way of comparing our inner workings with other people. Even brain scans are not 100% conclusive, see the link below.
I think it's easy to draw a flawed conclusion from research like this. While it can be shown that a majority of psychopathic serial killers have the prefrontal cortex brain anomaly, it's also the case that almost all such criminals are male. Yet we have an abundance of plainly apparent counterexamples to dismiss the idea that being male implies criminality. Interestingly, there are similarities here, as one of the largest brain differences between genders is in the development of the amygdala. The brain anomaly here concerns the connectivity between the prefrontal cortex and the amygdala.
> So the first thing I thought was that maybe my hypothesis was wrong, and that these brain areas are not reflective of psychopathy or murderous behavior.
> Eventually, based on further neurological and behavioral research into psychopathy, he decided he was indeed a psychopath—just a relatively good kind ...
It sounds to me as though he simply combined his finding with more research possessing the same systematic error, in order to support his conclusion, in spite of a counterexample. He then bends an established definition to suit his theory.
When sampling the extremes of a population (e.g. the most prolific murderers), combinations of compounding additive factors will naturally be common. To draw a causal link about any of them would be flawed, without a thorough and unbiased analysis of the rest of the population.
> While it can be shown that a majority of psychopathic serial killers have the prefrontal cortex brain anomaly, it's also the case that almost all such criminals are male. Yet we have an abundance of plainly apparent counterexamples to dismiss the idea that being male implies criminality
That's a bloody weird argument, and AFAICS wrong: (psychopath -> male) /-> (male -> psychopath), where -> is logical implication and /-> is is 'does not imply'. You are confusing implication with equality.
> with more research possessing the same systematic error ... in spite of a counterexample
What systematic error? What counterexample?
> without a thorough and unbiased analysis of the rest of the population
Sampling not good enough?
Serious question, do you have any background in either classical logic or statistics? And what is your area of research?
It seems there's a misunderstanding. According to me you are actually pointing to the same logical fallacy. The systematic error is indeed to think that correlation does imply causality. There's no more reason to think prefontal cortex anomaly causes psychopathy than being male does.
Indeed. Thanks for putting this more succinctly than I did.
I'd add that it's easier to observe the logical fallacy in the case of being male, because half of people are male, and being male is obvious. The occurrence of the PFC abnormality is much smaller, and we don't tend to see people's brains, so it's much harder to point to the counterexamples.
Blair, a researcher who pioneered research into psychopathic tendencies stated, “With regard to psychopathy, we have clear indications regarding why the pathology gives rise to the emotional and behavioral disturbance and important insights into the neural systems implicated in this pathology”.
From the same wiki article
Researchers have linked head injuries with psychopathy and violence. Since the 1980s, scientists have associated traumatic brain injury, such as damage to the prefrontal cortex, including the orbitofrontal cortex, with psychopathic behavior and a deficient ability to make morally and socially acceptable decisions, a condition that has been termed "acquired sociopathy", or "pseudopsychopathy".[72] Individuals with damage to the area of the prefrontal cortex known as the ventromedial prefrontal cortex show remarkable similarities to diagnosed psychopathic individuals, displaying reduced autonomic response to emotional stimuli, deficits in aversive conditioning, similar preferences in moral and economic decision making, and diminished empathy and social emotions like guilt or shame
> There's no more reason to think prefontal cortex anomaly causes psychopathy than being male does.
No, I'm not. This is the very point I was making. I was using the example (psychopath -> male) ^ !(male -> psychopath) to show how deducing (abnormal brain -> psychopath) from (psychopath -> abnormal brain) is flawed.
Perhaps I made this confusing with my tangential remark about the amygdala connection.
> What systematic error?
The systematic error of deducing a causality from correlation with under-sampling, in the aforementioned way the brain abnormality was determined to imply psychopathy despite neglecting to significantly sample occurrences of people with the prefrontal cortex abnormality in the non-murderous population.
> Sampling not good enough?
The sample has to be meaningful. If you find that everyone in the extremely rare serial killer group has a particular brain abnormality, you can't deduce that the brain abnormality causes their behaviour (rather than simply being prerequisite), without proving that this brain abnormality does not occur benignly within the non-serial killer population (to a significant degree). Because serial-killers are very rare (as far as we can observe), the sample of the remaining population would need to be very large.
If we were to sample such a large portion of the population as we would need to probabilistically rule out a given proportion of those with the abnormality being benign social individuals, then that would be convincing.
“Using MRI scans we found that psychopaths had structural brain abnormalities in key areas of their ‘social brains’ compared to those who just had ASPD,” he said.
He noted there is a clear difference between those with ASPD and those with ASPD+P.
“We describe those without psychopathy as hot-headed and those with psychopathy as cold-hearted,” he said.
“The cold-hearted psychopathic group begin offending earlier, engage in a broader range and greater density of offending behaviors, and respond less well to treatment programs in adulthood, compared to the hot-headed group. We now know that this behavioral difference corresponds to very specific structural brain abnormalities which underpin psychopathic behavior [my emphasis], such as profound deficits in empathizing with the distress of others.”
The researchers used magnetic resonance imaging (MRI) to scan the brains of 44 violent offenders diagnosed with ASPD. Crimes committed included murder, rape, attempted murder and grievous bodily harm. Of these, 17 met the diagnosis for psychopathy (ASPD+P) and 27 did not. Those that met the antisocial personality disorder but did not meet the psychopathy criteria (via the Psychopathy Checklist) were referred to as the ASPD-P group by the researchers. They also scanned the brains of 22 healthy non-offenders.
So they found a link, causal or not, between abnormalities and psychopathy, and they had a control group too.
> The systematic error of deducing a causality from correlation with under-sampling
I grant the control group here is small, but for you to claim it's 'under-sapled' is a bit cheeky. There seem to have been other studies too, from wikipedia "Blair, R. J. R. (2003). "Neurobiological basis of psychopathy". The British Journal of Psychiatry. 182 (1): 5–7. doi:10.1192/bjp.182.1.5. PMID 12509310." My guess is these people aren't so stupid as to overlook issues of under-sampling and mistaking correlation with causation.
> If you find that everyone in the extremely rare serial killer group has a particular brain abnormality [...] As serial-killers are very rare (as far as we can observe), the sample of the remaining population would need to be very large.
True, but psychopaths are neither rare nor automatically serial killers. If you're not equating them why did you mention serial killers?
Logical conjugation ("and"). I should have used ¬ instead of ! to have been more conventional.
> Is it [flawed to deduce (abnormal brain -> psychopath) from (psychopath -> abnormal brain)]?
Yes. That they show the group has a brain anomaly, and hypothesise a mechanism which links it to the behaviour is not enough. It's plausible that people who possess this brain abnormality within the rest of the population commonly are not psychopaths. You aren't going to find that within "22 healthy non-offenders", the sample is too small.
> So they found a link, causal or not, between abnormalities and psychopathy
I don't dispute this.
> There seem to have been other studies too, from wikipedia "Blair, R. J. R. (2003). "Neurobiological basis of psychopathy".
They aren't making the conclusion that the brain anomaly implies psychopathy, they only theorise a biological basis for it being foundational.
Furthermore their article they states: "However, all of these studies, with the exception of one by (Raine et al, 2000), have been with violent offenders rather than individuals with psychopathy. [...] Indeed, neuropsychological work with individuals with psychopathy, unlike work with individuals who are violent, has repeatedly found frontal functioning to be intact (Kandel & Freed, 1989)." This gives more weight to the argument that it is flawed to make deductions primarily by studying incarcerated offenders.
Neuropsychological studies are often compromising. Scanning brains is expensive. I don't believe that these researchers are stupid, as you asked, but it would be silly to say that scientists never theorise without concrete proof. Neurobiology is still highly hypothetical, and experiments are often very limited by practical and ethical concerns.
> why did you mention serial killers?
From the Smithsonian article: "neuroscientist James Fallon was looking at brain scans of serial killers."
33 comments
[ 4.2 ms ] story [ 79.9 ms ] threadWhile I do believe neuroscientists mostly know less than often implied, the research is very interesting.
He describes himself to be competitive, wrangling with his own ego. But wouldn't it be true then to say that he is no psychopath and a brain scan is insufficient for diagnosis?
And what is defined as healthy? Certainly not the absence of competitiveness or ego.
> But when he underwent a series of genetic tests, he got more bad news. “I had all these high-risk alleles for aggression, violence and low empathy,” he says, such as a variant of the MAO-A gene that has been linked with aggressive behavior. Eventually, based on further neurological and behavioral research into psychopathy, he decided he was indeed a psychopath—just a relatively good kind, what he and others call a “pro-social psychopath,” someone who has difficulty feeling true empathy for others but still keeps his behavior roughly within socially-acceptable bounds.
> It wasn’t entirely a shock to Fallon, as he’d always been aware that he was someone especially motivated by power and manipulating others, he says. Additionally, his family line included seven alleged murderers, including Lizzie Borden, infamously accused of killing her father and stepmother in 1892."
...
> “I’m obnoxiously competitive. I won’t let my grandchildren win games. I’m kind of an asshole, and I do jerky things that piss people off,” he says. “But while I’m aggressive, but my aggression is sublimated. I’d rather beat someone in an argument than beat them up.”
One of the defining characteristics of a psychopath is the lack of empathy. That is not to say you cannot learn when to feel empathic, and he touches on that too. Maybe we just need to change our definition, or invent a new one. One can be a pathological psychopath, but not be "a psychopath", because they was loved and cared for properly. Essentially they learned that social connections was overwhelmingly beneficial for them.
They do this by modelling social interactions and replaying them. It's more of a scripted response: "In this situation, act as if you feel like this."
I don't think they can learn to have genuine empathic feelings, because the part of the brain that would normally have them doesn't work very well.
It's not something good parenting can fix. It can maybe mitigate it to an extent, but it's not unusual for average-to-good parents to be completely baffled by a son/daughter with serious personality issues that are primarily genetic.
That question can't be answered without buttoning down the term. Generally diagnostic manuals don't recognise such a condition without actualized anti-social behaviour.
No it doesn't, that's a ridiculous generalisation, children are specifically taught to restrain their competitiveness by their role models reactions to it, it's not the amount of love they get, it's the priorities of parents, there are many noncompetitive people who received a lot of love as children.
Seriously, gross deformations of the brain, visible to the naked eye, are pretty dubious and questionable in my mind.
Meanwhile, the genetics that produce psychological disposition are more than hotly debated. Why? Because, think very carefully about where this story takes us. If we can say intellect is linked to genes, this puts a huge number of people in a box they cannot escape. Should the "dumb" people reproduce? Do we put laws in place so that only useful people have children?
Who is useless?
Are all people really created equal?
Also, the mechanics of how macro-scale neurology affects a person's psychology and sociology is still poorly understood, which makes the data especially easy to abuse. More than anything, I think the researcher's findings highlight this point; he was a counterexample to the theory that a diminished prefrontal cortex implies anti-social behaviour, showing the phenomenon to be more nuanced.
It means, that any competent researcher in a psychology would know ethical risks (due to education), and if he is testing his research plan on his family, he must be ready to find something unexpected, and he must inform participants on the risks.
[1] https://www.apa.org/ethics/
[2] https://en.wikipedia.org/wiki/Little_Albert_experiment
[3] https://www.simplypsychology.org/asch-conformity.html
[4] https://en.wikipedia.org/wiki/Stanford_prison_experiment
[5] https://www.simplypsychology.org/milgram.html
Breaking the double-blind restrictions of his study was an ethical breach. He was affecting the outcome by damaging a key instrument in the study (himself). Breaking the rules and being a maverick is sometimes useful, even ethical behavior, but in scientific research, if you go through all the effort to design a study, you should uphold the plan.
As far as all this psychopaths can be detected with a brain scan bs, well, it is just that--bs. I don't think there is an easy test to determine who is going to lead a life of crime and who isn't. I do think a lot of unsavory people rise to leadership roles. That is for certain. It would be nice if we could do something to control those types of people before they take such a huge toll on the rest of us.
What I found most annoying was his propensity for drawing easy conclusions about how his loving upbringing somehow prevented him from being another Lizzie Borden. Again, does this guy have any scientific training? There are tens of thousands of lurking variables unacknowledged there!
He's a psychopath.
They were specifically ones from his own family, so I imagine he had consent.
https://news.ycombinator.com/item?id=6787092
https://www.businessinsider.com/what-a-psychopath-brain-look...
You may get someone who is particularly aggressive and mean-spirited but who is generally honest, the opposite, and so on
> So the first thing I thought was that maybe my hypothesis was wrong, and that these brain areas are not reflective of psychopathy or murderous behavior.
> Eventually, based on further neurological and behavioral research into psychopathy, he decided he was indeed a psychopath—just a relatively good kind ...
It sounds to me as though he simply combined his finding with more research possessing the same systematic error, in order to support his conclusion, in spite of a counterexample. He then bends an established definition to suit his theory.
When sampling the extremes of a population (e.g. the most prolific murderers), combinations of compounding additive factors will naturally be common. To draw a causal link about any of them would be flawed, without a thorough and unbiased analysis of the rest of the population.
That's a bloody weird argument, and AFAICS wrong: (psychopath -> male) /-> (male -> psychopath), where -> is logical implication and /-> is is 'does not imply'. You are confusing implication with equality.
> with more research possessing the same systematic error ... in spite of a counterexample
What systematic error? What counterexample?
> without a thorough and unbiased analysis of the rest of the population
Sampling not good enough?
Serious question, do you have any background in either classical logic or statistics? And what is your area of research?
I'd add that it's easier to observe the logical fallacy in the case of being male, because half of people are male, and being male is obvious. The occurrence of the PFC abnormality is much smaller, and we don't tend to see people's brains, so it's much harder to point to the counterexamples.
You know, despite the trope sometimes it does. Does it here? From wikipedia <https://en.wikipedia.org/wiki/Psychopathy>:
Blair, a researcher who pioneered research into psychopathic tendencies stated, “With regard to psychopathy, we have clear indications regarding why the pathology gives rise to the emotional and behavioral disturbance and important insights into the neural systems implicated in this pathology”.
From the same wiki article
Researchers have linked head injuries with psychopathy and violence. Since the 1980s, scientists have associated traumatic brain injury, such as damage to the prefrontal cortex, including the orbitofrontal cortex, with psychopathic behavior and a deficient ability to make morally and socially acceptable decisions, a condition that has been termed "acquired sociopathy", or "pseudopsychopathy".[72] Individuals with damage to the area of the prefrontal cortex known as the ventromedial prefrontal cortex show remarkable similarities to diagnosed psychopathic individuals, displaying reduced autonomic response to emotional stimuli, deficits in aversive conditioning, similar preferences in moral and economic decision making, and diminished empathy and social emotions like guilt or shame
> There's no more reason to think prefontal cortex anomaly causes psychopathy than being male does.
It seems experts think otherwise.
No, I'm not. This is the very point I was making. I was using the example (psychopath -> male) ^ !(male -> psychopath) to show how deducing (abnormal brain -> psychopath) from (psychopath -> abnormal brain) is flawed.
Perhaps I made this confusing with my tangential remark about the amygdala connection.
> What systematic error?
The systematic error of deducing a causality from correlation with under-sampling, in the aforementioned way the brain abnormality was determined to imply psychopathy despite neglecting to significantly sample occurrences of people with the prefrontal cortex abnormality in the non-murderous population.
> Sampling not good enough?
The sample has to be meaningful. If you find that everyone in the extremely rare serial killer group has a particular brain abnormality, you can't deduce that the brain abnormality causes their behaviour (rather than simply being prerequisite), without proving that this brain abnormality does not occur benignly within the non-serial killer population (to a significant degree). Because serial-killers are very rare (as far as we can observe), the sample of the remaining population would need to be very large.
If we were to sample such a large portion of the population as we would need to probabilistically rule out a given proportion of those with the abnormality being benign social individuals, then that would be convincing.
> Serious question [...]
Yes; computer science.
> (psychopath -> male) ^ !(male -> psychopath)
I don't know what ^ means here, and !(m->p) is very different from (m/->p)
> to show how deducing (abnormal brain -> psychopath) from (psychopath -> abnormal brain) is flawed.
Is it? From <https://psychcentral.com/news/2012/05/11/scans-show-psychopa...
“Using MRI scans we found that psychopaths had structural brain abnormalities in key areas of their ‘social brains’ compared to those who just had ASPD,” he said.
He noted there is a clear difference between those with ASPD and those with ASPD+P.
“We describe those without psychopathy as hot-headed and those with psychopathy as cold-hearted,” he said.
“The cold-hearted psychopathic group begin offending earlier, engage in a broader range and greater density of offending behaviors, and respond less well to treatment programs in adulthood, compared to the hot-headed group. We now know that this behavioral difference corresponds to very specific structural brain abnormalities which underpin psychopathic behavior [my emphasis], such as profound deficits in empathizing with the distress of others.”
The researchers used magnetic resonance imaging (MRI) to scan the brains of 44 violent offenders diagnosed with ASPD. Crimes committed included murder, rape, attempted murder and grievous bodily harm. Of these, 17 met the diagnosis for psychopathy (ASPD+P) and 27 did not. Those that met the antisocial personality disorder but did not meet the psychopathy criteria (via the Psychopathy Checklist) were referred to as the ASPD-P group by the researchers. They also scanned the brains of 22 healthy non-offenders.
So they found a link, causal or not, between abnormalities and psychopathy, and they had a control group too.
> The systematic error of deducing a causality from correlation with under-sampling
I grant the control group here is small, but for you to claim it's 'under-sapled' is a bit cheeky. There seem to have been other studies too, from wikipedia "Blair, R. J. R. (2003). "Neurobiological basis of psychopathy". The British Journal of Psychiatry. 182 (1): 5–7. doi:10.1192/bjp.182.1.5. PMID 12509310." My guess is these people aren't so stupid as to overlook issues of under-sampling and mistaking correlation with causation.
> If you find that everyone in the extremely rare serial killer group has a particular brain abnormality [...] As serial-killers are very rare (as far as we can observe), the sample of the remaining population would need to be very large.
True, but psychopaths are neither rare nor automatically serial killers. If you're not equating them why did you mention serial killers?
Logical conjugation ("and"). I should have used ¬ instead of ! to have been more conventional.
> Is it [flawed to deduce (abnormal brain -> psychopath) from (psychopath -> abnormal brain)]?
Yes. That they show the group has a brain anomaly, and hypothesise a mechanism which links it to the behaviour is not enough. It's plausible that people who possess this brain abnormality within the rest of the population commonly are not psychopaths. You aren't going to find that within "22 healthy non-offenders", the sample is too small.
> So they found a link, causal or not, between abnormalities and psychopathy
I don't dispute this.
> There seem to have been other studies too, from wikipedia "Blair, R. J. R. (2003). "Neurobiological basis of psychopathy".
They aren't making the conclusion that the brain anomaly implies psychopathy, they only theorise a biological basis for it being foundational.
Furthermore their article they states: "However, all of these studies, with the exception of one by (Raine et al, 2000), have been with violent offenders rather than individuals with psychopathy. [...] Indeed, neuropsychological work with individuals with psychopathy, unlike work with individuals who are violent, has repeatedly found frontal functioning to be intact (Kandel & Freed, 1989)." This gives more weight to the argument that it is flawed to make deductions primarily by studying incarcerated offenders.
Neuropsychological studies are often compromising. Scanning brains is expensive. I don't believe that these researchers are stupid, as you asked, but it would be silly to say that scientists never theorise without concrete proof. Neurobiology is still highly hypothetical, and experiments are often very limited by practical and ethical concerns.
> why did you mention serial killers?
From the Smithsonian article: "neuroscientist James Fallon was looking at brain scans of serial killers."