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Finding Sociopaths on Facebook

schneier.com

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Re: Finding Sociopaths on Facebook

#21

Post by Samuel_Michon »

jokoon wrote: post #19
Samuel_Michon wrote: post #17

Earlier quoted context omitted.

Perhaps you’re thinking of people who are antisocial? I wouldn’t be surprised if some of the Facebook members who are most active and have the most ‘friends’ are sociopaths.

I have no real idea. I was just saying this, as in, I don't think criminal hang around facebook. If that'd be the case, would facebook just be some sort of crime catching tool ? I wonder though, is sociopathy a crime, or some trait that will turn people into criminal ? > I wouldn’t be surprised if some of the Facebook members who are most active and have the most ‘friends’ are sociopaths. I doubt the people you are t…

I’m not talking about crime. Most sociopaths never commit any crimes and it’s not illegal to be a sociopath. That would be silly, like jailing someone for having red hair. Also, it’s quite possible that there are more sociopaths than there are people with red hair – estimates range from 1% to 4% of the population.

> I don't think criminal hang around facebook.

Are you sure about that?

Re: Finding Sociopaths on Facebook

#22

Post by bandushrew »

anigbrowl wrote: post #18
paganel wrote: post #6

Earlier quoted context omitted.

> and guarantee that a quarter of the people on that list are terrorists, Honest question, what would happen to the other three quarters?

Most likely nothing. It depends on what sort of test it is; if it's something non-intuitive like (say) a habit of writing sentences that always have a prime number of words in them, you'll get your false positives but most those people won't pass any other tests, whereas the actual terrorists will. What Schneier is missing is that while you can't ID people that well from a single test, you can apply a bunch of them.…

Waiting until someone actually commits a crime provides a list that is 100% accurate.

Re: Finding Sociopaths on Facebook

#24

Post by fpgeek »

anigbrowl wrote: post #18
paganel wrote: post #6

Earlier quoted context omitted.

> and guarantee that a quarter of the people on that list are terrorists, Honest question, what would happen to the other three quarters?

Most likely nothing. It depends on what sort of test it is; if it's something non-intuitive like (say) a habit of writing sentences that always have a prime number of words in them, you'll get your false positives but most those people won't pass any other tests, whereas the actual terrorists will. What Schneier is missing is that while you can't ID people that well from a single test, you can apply a bunch of them.…

Applying multiple tests only works if the tests are independent. When you're searching for the proverbial needle in the haystack, you probably don't have enough needles to let you reliably calibrate several independent tests in the first place.

Re: Finding Sociopaths on Facebook

#25

Post by DanBC »

6ren wrote: post #12
DanBC wrote: post #2

An excellent post by Schneier. > The problem isn't just that such a system is wrong, it's that the mathematics of testing makes this sort of thing pretty ineffective in practice. It's called the "base rate fallacy." Suppose you have a test that's 90% accurate in identifying both sociopaths and non-sociopaths. If you assume that 4% of people are sociopaths, then the chance of someone who tests positive actually being…

I found his version clearer because "%" distinguishes proportions from quantities.

Yes, but imagine you're taking the test.

Suppose you have a test that's 90% accurate in identifying both people with X and people without X. If you assume that 4% of people are people with X and you're told that you test positive for someone who has X.

Do you really find it easy to arrive at your actual chance (26%) of having X? Let's not forget that most people on HN are at the smarter end of the bell curve. It'd be interesting to see the results of a large scale study about answers to questions like this.

Re: Finding Sociopaths on Facebook

#26

Post by ZeroGravitas »

coffeemug wrote: post #4
DanBC wrote: post #2

An excellent post by Schneier. > The problem isn't just that such a system is wrong, it's that the mathematics of testing makes this sort of thing pretty ineffective in practice. It's called the "base rate fallacy." Suppose you have a test that's 90% accurate in identifying both sociopaths and non-sociopaths. If you assume that 4% of people are sociopaths, then the chance of someone who tests positive actually being…

This is a pretty bad example to illustrate the fallacy because a 25% confidence is actually extremely good. I don't know what good a test for sociopathy is, but if we had a test this good at identifying terrorists, it would be incredibly useful. If signals intelligence could produce a list of people and guarantee that a quarter of the people on that list are terrorists, it would absolutely revolutionize law enforceme…

I think the fact that in this hypothetical 4% of all people are actually terrorists, and the potential terrorist list would be 10% of the total population, would have a greater impact on law enforcement than the accuracy of the test.

Even 0.4% of the population that get tested and are incorrectly "proved" innocent of being a terrorist amounts to more than a million undetectable terrorists in the US alone.

Re: Finding Sociopaths on Facebook

#28

Post by jkldotio »

paganel wrote: post #6
coffeemug wrote: post #4

Earlier quoted context omitted.

This is a pretty bad example to illustrate the fallacy because a 25% confidence is actually extremely good. I don't know what good a test for sociopathy is, but if we had a test this good at identifying terrorists, it would be incredibly useful. If signals intelligence could produce a list of people and guarantee that a quarter of the people on that list are terrorists, it would absolutely revolutionize law enforceme…

> and guarantee that a quarter of the people on that list are terrorists, Honest question, what would happen to the other three quarters?

They'd end up on a no fly list and be deprived of basic liberties to travel with no right to appeal secret courts and determinations. Or they'd get invasive checks even though they are a kid, or in a collapsible wheelchair and obviously not a terrorist.

All because people can't understand the example in question, which appears in the first few chapters of most introduction to statistics books. And while all that money is being spent on useless checks the 9/11 terrorists, who the agencies were warned about, and the Boston bombers, who the agencies were ALSO warned about, are not followed up on because human and other resources are being spent on mass surveillance.

Re: Finding Sociopaths on Facebook

#29

Post by 7952 »

smackay wrote: post #20
coffeemug wrote: post #4

Earlier quoted context omitted.

This is a pretty bad example to illustrate the fallacy because a 25% confidence is actually extremely good. I don't know what good a test for sociopathy is, but if we had a test this good at identifying terrorists, it would be incredibly useful. If signals intelligence could produce a list of people and guarantee that a quarter of the people on that list are terrorists, it would absolutely revolutionize law enforceme…

This issue has nothing to do with the efficacy of the tests. In a perfect world having a list where 25% of the names are potential trouble-makers (for various definitions of trouble-maker) would be an enormous benefit and allow resources to be targeted more efficiently. The real problem is what happens in the imperfect world where law enforcement, government, self-imposed officers of authority get lazy or down-right…

The best outcome would be for these kind of traits to be passively detected and for the community to provide help and support as an emergent property of that community. In a way this already happens on sites like Reddit where suicide prevention emerged organically based on the dynamics of the community. This is in stark contrast to the "real world".

The internet is well known as a negative influence on certain people, but couldn't it be having a positive effect that is harder to measure and more an unintended side effect.

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