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Comment by dsacco | Hacker News Reader

> But my understanding from an Intro to Psych class that I had years ago is that serial killers typically have six traits, including high IQ, plus other traits we would consider sociopathic, like lack of empathy.

Your understanding is incorrect. Serial killers do not typically have high IQs.[1] In fact they have normal IQs on average, and typically present themselves within a standard deviation of the norm.

The high IQ serial killer is a popular meme, but is ultimately unfounded.

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1.http://maamodt.asp.radford.edu/Serial%20Killer%20Information...

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Television-serial serial-killers typically have high IQs. It's the part of the conceit that keeps the character from getting caught, so they can keep making new episodes. They're smart enough to stay one step ahead of the law, but the chief investigator is also smart, so the killer can never get more than two steps ahead. The possibility of getting caught out from just one misstep keeps the tension in the show.

Real serial killers are average intelligence, chased by cops with average intelligence. They get caught for the same reasons that get other criminals collared. They get sloppy, and they fall into predictable patterns, or the cops get lucky. The only reason they can commit the same crime multiple times is that real investigative police work is difficult without CSI-style magical technology. Most people could formulate a simple set of rules that would keep their crimes separate from their public identity--until one of them hits a corner case and leaks critical information.

Don't burgle houses with dogs. Always burn the clothes you wore. Never look inside the package. Use encryption and dead drops. Put thermite on incriminating storage devices. Never work the same postal code twice. Don't work with a pimp. Always pay the boss exactly what you owe. Don't surface the submarine until you get within 50m of the floating dock. Wives and kids are off limits. Don't spend your share conspicuously. Don't sample the goods. Don't talk about Project Mayhem. &c. &c. &c.

It doesn't require mastermind-level plotting. The hardest part about crime is finding a person willing to do it. A lack of empathy goes a long way towards that, and an unwillingness to take responsibility for the consequences of one's actions gets even closer. The smart criminals don't murder people; instead they go into real-estate fraud, money laundering, and insider trading. The money is better and the prosecutions rarer.

There's an excellent book called How to lie with statistics. It goes into detail about the various ways you can package the same data to support whatever point you want to make. Having read that book more than once, I like to try to dig into the guts of the data, if possible, to see if it really says what people claim it says, which is very often not the case.

The piece you link to lists the lowest IQ as Simon Pirela with an IQ of 57. I found the following two pieces about Pirela:

http://caselaw.findlaw.com/us-3rd-circuit/1874807.html

http://articles.chicagotribune.com/2004-05-02/news/040502046...

He was apparently involved in four murders, but I am failing to find good details. From what I am reading of the one case where I can find a few details, you could conclude he was pressured into helping commit murder by other people and this occurred in part due to his low IQ. They commuted the death sentence due to his disability. So even the law doesn't hold him fully responsible.

The research you cite lists people as serial killers who killed at least two people. I don't think this is really what most people have in mind when talking about serial killers. Other research defines it differently, only including people who have killed at least three people.

Saying that someone typically has a high IQ doesn't mean they always have a high IQ. If you drop the very low figure of Simon Pirela's 57 IQ from the data, I imagine that would substantially change the means, medians, etc. cited.

My best understanding is that serial killers are typically bright. And the link you have provided is not really compelling evidence to the contrary.

I have spent part of my afternoon looking at this information because a. I did take Intro to Psych a long time ago, so perhaps what I know is outdated and b. I have a sincere interest in knowing what the truth is. That matters far more to me than winning internet arguments. I'm not here to argue with anyone anyway. That's not what motivates me.

But I'm really not finding your source compelling. So my mind has not been changed. I see no reason to believe the stated conclusion of this piece is better information than what I have previously been told. In fact, it looks pretty sketchy to me.

I'd recommend looking at the source of this information more closely: http://maamodt.asp.radford.edu/Serial%20Killer%20Information... on page 12 it breaks down the statistics relating IQ and serial killers. While you might find reason to disagree with 2 murders as sufficient to warrant the serial killer title (for the record, the reason they include 2 is because that is the official FBI definition), that breakdown shows what the average IQ is for those who committed three murders, 4 murders, and 5 or more. It also breaks things down by organized vs. disorganized killers, whether or not they raped victims, and the method of killing, and the N value for each subset. The only breakdown with an average greater than a standard deviation from average is for the serial killers that killed using bombs. And that it because it's only N=3 and includes Ted Kaczynski. Also keep in mind the median IQ is 86, and removing a couple of data points like Simon Pirela will have little effect on that value.

I can also give a personal citation of my own if that might help convince you. My Dad is a clinical psychologist who gives lectures on Conduct Disorder and Antisocial Personality Disorder, and does work for the courts evaluating the mental competency of defendants. He's the one who first told me there is no correlation between serial killers and intelligence.

Unless I am missing something, that's 20 pages of aggregate stats on things like age, race and gender. There is very little info here about IQ. It doesn't give me the data I need to draw meaningful conclusions.

It breaks down the average IQ based on the number of victims, which is what you mentioned in your comment. You said that defining serial killer as having at least 2 victims is too low. But this data has the IQ averages for those who killed three or more, four or more, etc. And in all cases it shows the average as being between 90 and 100. All of this data is just basic aggregates from the Serial Killer Database (http://skdb.fgcu.edu/info.asp) by the way, if you're skeptical of the source. Is there something specific you need?

Aggregated data is part of the problem. And even in that small data set, the average IQ trends up as the number of victims trends up. It comes a lot closer to average IQ than the overall number of 86, but it does trend up.

The piece you linked to seems to have an explicit political agenda of disproving the popular image of a serial killer as a young white male. And that makes the entire database questionable because if that is the goal, then you explicitly define things as broadly as possible so as to accomplish your political agenda.

I'm aware there are legitimately different profiles of serial killers. For example, your typical female serial killer has murdered multiple relatives by poisoning for the insurance money. This is very different from your typical male serial killer.

At this point I am tired and frustrated and I don't know how to sort out the answer to this question. I know we have IQ scores for a number of high profile cases that clearly fit my understanding of what a serial killer is and those IQs are on the high side, fitting my general understanding. I don't know where to look for data that doesn't have a political agenda of explicitly rebutting popular perception. For the moment, I feel stymied. And the reality is this is not important enough for me to keep digging into the question indefinitely. It's already eaten an excess of my time.

>Aggregated data is part of the problem.

Even more so than confirmation bias?

>And even in that small data set, the average IQ trends up as the number of victims trends up. It comes a lot closer to average IQ than the overall number of 86, but it does trend up.

Obviously, duh. It's not because serial killers tend to be of higher IQ, but because serial killers of higher IQ can get uncaught for longer, and thus manage bigger "number of victims".

Correlation != causation and all.

Very interesting research, thank you for linking. I only wish they'd broken out IQ by broad motive, I imagine it would differ between those doing it for "thrill/lust/power" vs "financial gain".

> My best understanding is that serial killers are typically bright. And the link you have provided is not really compelling evidence to the contrary.

Your understanding is incorrect. But I read How to Lie With Statistics too, so I'm happy to help you with more sources for your perusal. Keep in mind that merely invoking How to Lie With Statistics does not refute a statistical analysis, you actually have to identify the problem.

1. This document goes into much greater depth about the statistics you're criticizing: http://maamodt.asp.radford.edu/Serial%20Killer%20Information..., including a coverage of serial killers with 2 or more versus 3 or more victims.

2. The FBI's profile of serial killers, from their behavioral science unit, in which they explicitly call out the popular conception of high IQ serial killers as being a myth: https://www.fbi.gov/stats-services/publications/serial-murde...

3. This study conducts a meta analysis of published literature that finds no correlation between verbal intelligence and traits traditionally associated with psychopathy: https://www.ncbi.nlm.nih.gov/m/pubmed/28836093/ (also on bioRxiv if you'd like to read the non-paywalled version).

4. This study finds that, for a set of intelligence metrics and psychopathy checklist traits, psychopathy and intelligence are orthogonal: http://journals.sagepub.com/doi/abs/10.1177/0093854807309806

5. For good measure, since you like popular media like true crime TV, I'll throw in a Scientific American article for you: https://www.scientificamerican.com/article/5-myths-about-ser...

> But I'm really not finding your source compelling. So my mind has not been changed.

I suppose I should be transparent with you: I don't debate with people online to persuade them, I debate with people online to persuade the audience. I don't particularly mind if you're convinced, but it is important to me that misinformation not be spread unchallenged. So now we're at a crossroads. I've provided empirical evidence from a variety of cited sources, and you've provided an anecdote from an undergraduate course you took years ago. My sources might be incorrect! The beauty of science is that you can challenge its findings. I welcome you to challenge the sources I've provided as well (though I'd remind you that you've continually abstained from providing any of your own). But if you don't, that's also totally fine, because I think I've sufficiently demonstrated my point either way. Considering your lukewarm dismissal of an academic dataset based on a disagreement with one particular data point out of 206, it appears true crime television and your recollection of an old psych class are better authorities than published research.

Considering your lukewarm dismissal of an academic dataset based on a disagreement with one particular data point out of 206

I can't find info on the other 204. I see 2 names listed, one a famous case I already had heard about. So I tried to find details on the only other data point where I was provided a name and came up short on the kind of info I would like to see.

Your comments are not written in a good faith fashion. I don't plan to engage you further.

Do you plan on addressing the other four citations he provides? Or, even better, providing a citation of your own?

Off topic: It's always strange to see my alma mater in the wild (Radford University)

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