(not by Parker Bros., or, for that matter, Waddingtons)
A response to: 3 Levels of Rationality Verification
Related to: Diplomacy as a Game Theory Laboratory
It's a classic who-dun-it…only instead of using an all-or-nothing process of elimination driven by dice rolls and lucky guesses, players must piece together Bayesian clues while strategically dividing their time between gathering evidence, performing experiments, and interrogating their fellow players!
Hematology Lab -- bring a blood sample over here, and you can find out one bit of information about the serotype…is it A or O? B or O? + or - ? The microscope knows. Don't know how to use a microscope? Try reading up on it in the Library.
Autopsy Table -- bring a body part over here, and you can take an educated guess as to what kind of weapon caused the murder wounds. (Flip over 1 of 10 cards, 4 of which show the correct murder weapon and 6 of which are randomly distributed among the other five weapons.) The error in guesses doesn't correlate across body parts, so if you personally examine enough of them, or if you can persuade your fellow dinner-guests to bust out all the body parts at the same time, you should be able to get the right answer.
Lie Detector -- bring a fellow player over here, and you can ask him/her a yes-or-no question and get some evidence as to whether it was answered honestly. Have the answerer roll a D10, add a secret constant unique to his/her character, multiply the sum by the truth value of his/her statement (1 for true, 2 for false), and then look up the number on a chart that returns the value "stress" or "no-stress." It's up to the interrogator to figure out the correlation (if any) between stress and lying for each player! How do you get the other player into the Lie Detector room in the first place? Good question! When you figure it out, let me know…I have a paper I'd like you to co-author with me on the Prisoner's Dilemma.
Plus the usual collection of Kitchens, Billiards Rooms, Parlours, and so forth. One room is inaccurately labeled.
PIECES OF EVIDENCE:
If you spend your turn searching a room, you might find…
Blood stains -- most of them are either from the murderer or the victim, but some are not. You can take a sample so as to carry it with you to the Hematology Lab.
Body parts -- all of them belong to Mr. Boddy, and all the parts are nice and portable…just the right size to shove one in your pocket and dash back to the autopsy table to sneak a peek by yourself. Of course, if you're feeling cooperative, it might be more efficient to get the gang together and lay all your cards, er, on the table, at the same time.
Video footage of the murder -- just kidding. What kind of game did you think you were playing here, anyway?
WHERE DID THE MURDER TAKE PLACE?
The game rules chattily assure you that the murder did not take place in the Lab, on the Table, or by the Detector…but of course this is simply disinformation coming from a source that you are likely to erroneously assume is authoritative, even though you have no firm evidence that the rulebook is a reliable narrator.
You don't need to know where the murder took place to win, as each player only gets one guess, and there are 36 weapon * character possibilities, which is a lot to sift through with just a handful of sadistic clues. However, for bonus points, you can try noticing that most of the useful clues come from the same room, and that the murderer knows where (s)he killed Mr. Boddy, so if you ask real nicely you might be able to ask him/her a few thoughtful questions over at the Lie Detector.
HOW DOES THE GAME END?
Once you realized Mr. Boddy had been killed on a dark, snowy night that shut down all travel in and out of the mansion, one of you took the precaution of activating the house's high-tech security cameras -- the murderer will not kill again this night. Rather, you will all dither endlessly until all but one of you can agree on a prime suspect, at which point you will join forces, handcuff him or her to the telescope in the Observatory, and wait for the snowplow to come through and the police to arrive, at which point you will find out just how right (or wrong) you were.
This has the distinct advantage that if most people want to stop playing they can rule-fully end the game at any time.
Note, by the way, that while I hope at least some parts of my description are funny, this is not really a joke -- I would like to design this board game and then playtest it with casual Less Wrong readers to see if it motivates us or otherwise helps us to test, develop, or practice rationality skills. If you have feedback about either the game's playability or its educational value, I'd love to hear it.