I was somewhat disappointed to find a lack of Magic: the Gathering players on LessWrong when I asked about it in the off-topic thread. You see, competitive Magic is one of the best, most demanding rationality battlefields that I know about. Furthermore, Magic is discussed extensively on the Internet, and many articles in which people try to explain how to become a better Magic player are, essentially, describing how to become more rational: how to better learn from experience, make judgments from noisy data, and (yes) overcome biases that interfere with one's ability to make better decisions.
Because people here don't play Magic, I can't simply link to those articles and say, "Here. Go read." I have to put everything into context, because Magic jargon has become its own language, distinct from English. Think I'm kidding? I was able to follow match coverage written in French using nothing but my knowledge of Magic-ese and what I remembered from my high school Spanish classes. Instead of simply linking, in order to give you the full effect, I'd have to undertake a project equivalent to translating a work in a foreign language.
So it is with great trepidation that I give you, untranslated, one of the "classics" of Magic literature.
Stuck In The Middle With Bruce by John F. Rizzo.
Now, John "Friggin'" Rizzo isn't one of the great Magic players. Far from it. He is, however, one of the great Magic writers, to the extent that the adjective "great" can be applied to someone who writes about Magic. His bizarre stream-of-consciousness writing style, personal stories, and strongly held opinions have made him a legend in the Magic community. "Stuck in the Middle with Bruce" is his most famous work, as incomprehensible as it may be to those who don't speak our language (and even to those that do).
So, why am I choosing to direct you to this particular piece of writing? Well, although Rizzo doesn't know much about winning, he knows an awful lot about what causes people to lose, and that's the topic of this particular piece - people's need to lose.
Does Bruce whisper into your ear, too?
The thing about magic which sets it apart in terms of rationality training is that you can't go at it with theory alone. It takes hours of experimentation to get your deck built right, testing a variety of maindeck and sideboard permutations until you find one which is optimal against the current metagame**. As soon as the metagame changes, it's back to testing. Since magic is never "solved," at least not permanently, it forces you to become good at coming up with guesses and testing them, at least within this specific domain.
terms for the bewildered:
*maindeck and sideboard: your deck consists of at least 60 cards in the maindeck and exactly 15 in the sideboard. During a match (at least 3 games, sometimes 5) after the first and second games, you can trade cards from your maindeck for cards in your sideboard.
**metagame: the game outside the game, in other words, the different decks you are likely to face. In any given format, there are usually a handful of strong decks which dominate the field in some variation or another. As such, you end up playing against them more often then other decks.