As many of you probably know, in an Italian court early last weekend, two young students, Amanda Knox and Raffaele Sollecito, were convicted of killing another young student, Meredith Kercher, in a horrific way in November of 2007. (A third person, Rudy Guede, was convicted earlier.)
If you aren't familiar with the case, don't go reading about it just yet. Hang on for just a moment.
If you are familiar, that's fine too. This post is addressed to readers of all levels of acquaintance with the story.
What everyone should know right away is that the verdict has been extremely controversial. Strong feelings have emerged, even involving national tensions (Knox is American, Sollecito Italian, and Kercher British, and the crime and trial took place in Italy). The circumstances of the crime involve sex. In short, the potential for serious rationality failures in coming to an opinion on a case like this is enormous.
Now, as it happens, I myself have an opinion. A rather strong one, in fact. Strong enough that I caught myself thinking that this case -- given all the controversy surrounding it -- might serve as a decent litmus test in judging the rationality skills of other people. Like religion, or evolution -- except less clichéd (and cached) and more down-and-dirty.
Of course, thoughts like that can be dangerous, as I quickly recognized. The danger of in-group affective spirals looms large. So before writing up that Less Wrong post adding my-opinion-on-the-guilt-or-innocence-of-Amanda-Knox-and-Raffaele-Sollecito to the List of Things Every Rational Person Must Believe, I decided it might be useful to find out what conclusion(s) other aspiring rationalists would (or have) come to (without knowing my opinion).
So that's what this post is: a survey/experiment, with fairly specific yet flexible instructions (which differ slightly depending on how much you know about the case already).
For those whose familiarity with the case is low:
I'm going to give you two websites advocating a position, one strongly in favor of the verdict, the other strongly opposed. Your job will be to browse around these sites to learn info about the case, as much as you need to in order to arrive at a judgment. The order, manner, and quantity of browsing will be left up to you -- though I would of course like to know how much you read in your response.
1. Site arguing defendants are guilty.
2. Site arguing defendants are innocent.
I've chosen these particular sites because they seemed to contain the best combination of fierceness of advocacy and quantity of information on their respective sides that I could find.
If you find better summaries, or think that these choices reflect a bias or betray my own opinion, by all means let me know. I'm specifically avoiding referring you to media reports, however, for a couple of reasons. First, I've noticed that reports often contain factual inaccuracies (necessarily, because they contradict each other). Secondly, journalists don't usually have much of a stake, and I'd like to see how folks respond to passionate advocacy by people who care about the outcome, as in an actual trial, rather than attempts at neutral summarizing. Of course, it's fine if you want to read media reports linked to by the above sites.
(One potential problem is that the first site is organized like a blog or forum, and thus it is hard to find a quick summary of the case there. [EDIT: Be sure to look at the category links on the right side of the page to find the arguments.] If you think it necessary, refer to the ever-changing Wikipedia article, which at the moment of writing seems a bit more favorable to the prosecution. [EDIT: I'm no longer sure that's true.] [EDIT: Now I think it's true again, the article having apparently changed some more. So there's really no telling. Be warned.])
After you do this reading, I'd like to know:
1. Your probability estimate that Amanda Knox is guilty.
2. Your probability estimate that Raffaele Sollecito is guilty.
3. Your probability estimate that Rudy Guede is guilty.
4. How much you think your opinion will turn out to coincide with mine.
Feel free to elaborate on your reasoning to whatever degree you like.
One request: don't look at others' comments until you've done the experiment yourself!
For those whose familiarity with the case is moderate or high:
I'd like to know, as of right now:
1. Your probability estimate that Amanda Knox is guilty.
2. Your probability estimate that Raffaele Sollecito is guilty.
3. Your probability estimate that Rudy Guede is guilty.
4. How much you think your opinion will turn out to coincide with mine.
5. From what sources you've gotten the info you've used to arrive at these estimates.
Then, if possible, do the experiment described above for those with little familiarity, and report any shifts in your estimates.
Again, everyone should avoid looking at others' responses before giving their own feedback. Also, don't forget to identify your prior level of familiarity!
If the level of participation warrants it, I'll post my own thoughts (and reaction to the feedback here) in a later post. (Edit: That post can be found here.)
Not true. A perfect Bayesian updater will never make worse decisions in the light of new information. If new information causes worse decisions that is a reflection that the new information was not appropriately weighted according to the trustworthiness of the information source.
In other words, false information can only make for worse decisions if it is treated as true. The only reason you would treat false information as true is that you placed too much trust in the source of the information. The problem is not the receipt of the new information, it is incorrect updating due to incorrect priors regarding the reliability of the information source. That may be a common problem for actual imperfect humans but it is not an indication that acquiring new information can ever lead to worse decisions for a theoretical perfect Bayesian updater.
That's not quite right. The provision of all true but biased information (e.g. only those facts that are consistent with guilt) without complete awareness of the exact nature of the bias applied can increase the chances of an error.
Even unbiased info can't be said to always help. A good example is someone who has crazy priors. Suppose someone has the crazy prior that with probability .99999 creationism is true. If they have somehow aquired evidence that overcomes this prior but further information about problems with evolutionary theories would leave t... (read more)