[Violet-Rose]

I've heard on the internet rumours that police and career criminals have nearly identical psychological profiles and I wondered if it was true?

If it is could someone link me to an article that says more?

[PhDwannabe]

The origins (maybe not the original ones, but those substantially responsible for its enduring popularity) come from old reports associated with a still-widely used self-report personality measure, the MMPI (or Minnesota Multiphasic Personality Inventory). The MMPI was developed in a time in which factor analysis (a new statistical technique which could pull out factorial patterns in large chunks of data) was thought to hold great promise in showing us the fundamental sub-units of big constructs like intelligence, personality, and psychopathology.

The MMPI was almost completely empirically derived--you ask your validation sample a billion questions, see which ones are endorsed positively by the people who are nutty in particular ways, ergo, those questions come to denote particular kinds of nuts. So, it's not theory-driven, per se. You could ask "I always think desk chairs don't lean back far enough" and find that it's almost always endorsed positively by really anxious people. You might have no idea what this really has to do with anxiety, but the data are the data, so this item becomes part of an anxiety scale. This is actually one of the cool things about the measure: it often has relatively low face-validity (the person can't always tell what this question is really measuring, so it's theoretically tougher to fake things.) Through this process (it's a bit more complicated, but these are the basics) they generated ten clinical scales corresponding to many of the large issues psychiatry was facing at the time--they've retained some of their old-timey psych names, much to our current amusement.

When people take the measure, we plot all of their scale scores on a chart and look for elevations. Their pattern of elevations is expressed by naming the two or three most elevated scales in order, like this: "the patient has a 2-0-6 profile," which would correspond to elevations on the Depression, Introversion, and Paranoia scales. The idea was that we could do all sorts of big studies and establish what patterns of scale elevation corresponded exactly to certain conditions--we'd have a big body of data we could use to find out what Mr. 2-0-6 was like, and how his condition would progress, etc. We still have the results of many of these efforts (we call them "cookbooks.")

So, bottom line, much of this has not panned out exactly as planned. That's another discussion in itself, but to get (finally) to your question: there's a response pattern--a quite famous one--known as a "4-9," corresponding to elevations on the Psychopathic Deviate and Hypomania scales. We're talking here about somebody who's somewhat agitated or easily excitable, and who doesn't have a lot of respect for society's usual rules. Essentially, we're talking about people with what we'd now usually diagnose as Antisocial Personality Disorder (ASPD).

The old story goes that there are two populations you find a lot of 4-9s in: incarcerated criminals, and police academy graduates. Look, I have no idea if this is even true. This scale has been around for so long, it's gone around and around, and you're likely to find a study that supports, and a study that does not support, any given relationship you can think of between a code type and a behavior or population difference of some kind. A cursory google doesn't give me much on the matter, my area of psych expertise is decidedly not personality assessment, and this also happens to be the area of empirical literature I really least like poking around in, so I'm ducking out of that job. But I can tell you that the 4-9/criminals/cops story has been going around forever, and whether it is based in any fact or isn't, it's a large part of the foundation for the rumor you've heard.

This post has been edited by PhDwannabe: 27 August 2011 - 03:04 PM

[Violet-Rose]

Wow. that was absolutely riveting reading. Thank you