In the book "The Sociopath Next Door: The Ruthless vs. the Rest of Us" by Martha Stout Ph.D. (Broadway Books, New York, 2005, ISBN 0-7679-1581-X) the author claims that 1 in 25 people are sociopaths. (It is referenced here)

I'm sure I've heard that statistic before, but I've never heard it explained or elaborated. How could anyone really know that? Is there a way to prove a person is a sociopath unless they are willing to provide honest answers?

There are additional claims that sociopaths are disproportionately represented among the prison population.

Again, how can anyone know that? Isn't it possible that some may not answer questions of remorse honestly?

Basically, is there any objective test for Antisocial Personality Disorder?

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    Here at Skeptics, it's about 2 in 3. ;) Commented Sep 15, 2011 at 18:42
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    I assume this claim would require a pretty liberal definition... Commented Sep 15, 2011 at 19:30
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    No. No. No. No. Yes. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. Commented Sep 15, 2011 at 19:34
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    I've had a researcher come and ask me if I'm a sociopath once. I had a nice dinner with fava beans and a bottle of Cianti... but something was missing.
    – user5341
    Commented Sep 15, 2011 at 21:05
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    I'm not a sociopath, I hate everyone. None of you are real, anyway.
    – Darwy
    Commented Sep 19, 2011 at 12:09

2 Answers 2


The National Institute of Mental Health says it's 1 in 100 and that it's more likely to find Antisocial Personality Disorder (the DSM-IV term) in men.

For some reason, they stuck the information in an image

The link cites data from the National Comorbidity Survey, which you can find more about here and specifics regarding how they make dianoses here. Here is a PDF talking about how they select interviewees and do their interviews. To sum it up, 300 trained professionals went out and personally interviewed around 10000 people in the continental US once and then did follow-up interviews with around half of them.

That does line up with what my professors were telling me in college, but I can't very well cite my old notes here. They were probably just quoting me figures from the NCS, too.

Here is a PDF that talks about the five axis diagnosis process, since that's also relevant to part of your question.

The MMPI is supposed to be pretty good at picking out different disorders.

  • Thanks for that, but NIMH doesn't explain their methodology, and only lists a survey. Is this based on interviews of sociopaths who seek treatment? I still don't see whether there's an objective test or if this is all just highly sample biased data Commented Sep 15, 2011 at 22:09
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    @Michael - All determinations of abnormality are relative to the population norm, so if you're looking for something like a blood test that shows the psychopath protein, you're SOL.
    – dtanders
    Commented Sep 15, 2011 at 22:21
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    Fair enough, but if they're using self-reporting as a diagnostic method for a condition which those affected are likely to lie about for a number of social reasons then I'm not sure the measurement is very useful. Do you know what methodology they used? Was it based on diagnoses made after crimes, or self committing individuals or a large screening done over a population for some reason? Commented Sep 15, 2011 at 22:50
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    @Michael - Added a couple links to the NCSR information site. It's very informative because there's a lot of information and no paywalls that I could see. Basically, trained professionals personally interviewed several thousand people, so there was self-report involved, but it was exactly the same amount you would have if you went to a therapist. I'll also try to find a good explanation of how the MMPI detects personality disorder, but I rather doubt I'll find one as good as my old notes.
    – dtanders
    Commented Sep 16, 2011 at 13:38
  • Great answer and thanks for putting up with my (nearly) endless questions. It's people like you who make this site great :) Commented Sep 19, 2011 at 23:17

Dtander's answer is quite alright, but because you kept asking about the problem with self-report:

First: There is hardly any incentive to pretend that you don't feel empathy, so an estimate that we get from self-report would be lower-bound (if the criteria are proper).

Secondly, sociopath, psychopath, dissocial and antisocial personality disorder are not exactly the same concepts depending on who you ask. For example Hervey Cleckley has asserted that psychopaths are immune to suicide but there is differential evidence for two factors that Hare's PCL-R comprises.
So some argue that the deviancy/delinquency without lack of empathy/remorse is antisocial personality disorder, and the afflicted will sometimes seek help. I'm not on top of the debate, but I'd say it's likely that it will not come to an inherent endorsement of the term "psychopath" because it has a quite "evil" connotation (the Stout book sounds quite scaremongering as well) and the people Hare means wouldn't seek help anyway.

Third, not all of the criteria in antisocial/dissocial personality disorder and even fewer in the PCL-R need to be based on self-reports. There are case files about activities like (juvenile) delinquency, many short-term marital relationships, promiscuity, etc.
And not all think they have something to hide. A quote from Geoffrey Miller's Mating Mind:

Very few psychopaths flaunt their lack of sympathy like Hannibal Lecter, because very few of them are glamorous, urbane geniuses. Mostly, they are just ordinary creeps who beat their girlfriends, stab guys in bars for no reason, get caught, and then apply for parole four times as often as non-psychopaths because they don't think they've done anything wrong.

Fourth, I'd say the MMPI isn't good, it's just widespread. The SKID and the DIPS are supposed to be better. Many prefer the MMPI though for reasons such as sunk cost and the ability to fax your answer sheets in to get a score.
Can't dig up an English reference now, sorry.
Hank, P.,& Schwenkmezger, P. (2003). Das Minnesota Multiphasic Personality Inventory-2 (MMPI). Testbesprechung im Auftrag des Testkuratoriums. Report Psychologie, 28(5), 294-303.

  • Thanks for this answer. It dose follow up on a lot of my questions. I do have to take issue with the "no incentive to lie" part. There are huge social and economic costs to being outed as a sociopath. Granted, the interviews are bound by a confidentiality agreement. I'd wonder if a true sociopath would doubt if anyone could abide by such an agreement and thus not trust it. Just a thought, but seeing as I don't have another suggestion I suppose it doesn't amount to much. Plus good point on using physical evidence to supplement a diagnosis (crime, divorce, etc). Commented Sep 19, 2011 at 23:21
  • @Michael There is hardly any incentive to pretend you're a sociopath because of the costs you mention (I'll spell it out more clearly in the answer). Thus, a lower-bound estimate of true prevalence.
    – Ruben
    Commented Sep 21, 2011 at 15:52
  • @Ruben The question is about whether 4% of people are psychopath. The answers that based on the MMPI got 1%. As you say the MMPI likely produced a lower bound estimate. Is there reason to believe that the true prevelance might in fact be 4% or higher?
    – Christian
    Commented Nov 2, 2012 at 13:21
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    @DVK Don't fall for that pick up line. I saw you commented on the relevant question which gives a more nuanced version of that statement (so you should know better) and still comes out in favour of "bad boys" too much. Also, "unable to put yourselves in someone else's shoes" is probably not how most people would define your prototypical bad boy. Maybe "unwilling". Do you think people would advertise a "parasitic lifestyle" and "many short-term marital relationships" to impress the "cute interviewer"?
    – Ruben
    Commented Mar 13, 2013 at 9:19
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    @Jack I didn't assert that. It's one of the things on Hare's checklist, not sure how well supported, but also: all Greeks are humans, but not all humans are Greeks. Don't use promiscuity as an index of psychopathy please.
    – Ruben
    Commented Oct 24, 2014 at 11:56

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