You’re the captain of a team, and you want to select really good players. How do you do it?
One way is through what I call positive selection. You devise a test – say, who can run the fastest – and pick the people who do best. If you want to be really strict, like if you’re selecting for the Olympics, you only pick the top fraction of a percent. If you’re a player, and you want to get selected, you have to train to do better on the test.
The opposite method is negative selection. Instead of one test to pick out winners, you design many tests to pick out losers. You test, say, who can’t run very well when it’s hot out, and get rid of them. Then you test who can’t run very well when it’s cold out, and get rid of them. Then you test running in the rain, and get rid of the losers there. And so on and so forth. When you’re strict with negative selection, you have lots and lots of tests, so that it’s very hard for any one person to pass through all the filters.
I think a big part of where American society’s gone wrong over the last hundred years is the ubiquitous use of negative selection over positive selection. (Athletics is one of the only exceptions. It’s apparently so important that people really care about performance – as opposed to, say, in medicine, where we exclude brilliant doctors if they don’t have the stamina to work ninety hours a week.) A single test can always be flawed; for example, IQ tests and SATs have many flaws. However, with negative selection, how badly you do is determined by the failure rate of every test combined. If you have twenty tests, and even one of them is so flawed it excludes good players, then your team will suck.
Elite college admissions is an example of a negative selection test. There’s no one way you can do really, really well, and thereby be admitted to Harvard. Instead, you have to pass a bunch of different selection filters: Are your SATs good enough? Are your grades good enough? Is your essay good enough? Are your extracurriculars good enough? Are your recommendations good enough? Failure on any one step usually means not getting admitted. And as competition has intensified, colleges have added more and more filters, like the supplemental applications top schools now require (in addition to the Common Application). It wasn’t always this way – Harvard used to admit primarily based on an entrance exam – until they discovered this let too many Jews in (no, seriously). More recently, the negative selection has been intensified by eliminating the SAT’s high ceiling.
Academia is another example of negative selection. To get tenure, first you have to get into a top PhD program. Then you have to graduate. Then you have to get a good recommendation from your advisor. Then you have to get a good postdoc. Then you have to get another good postdoc. Then you have to get a good assistant professorship. Then you have to get approved by the tenure committee. For the most part, if even one of those steps goes wrong – if you went to a second-tier PhD program, say – there’s no way to recover. Once you’re off the “track”, you’re off, and there’s no getting back on. It’s fail once, fail forever.
Grades are another example – A is a good grade, but there’s no excellent grade. There’s no grade that you only get if you’re in the top 0.1%. Hence, getting a really good GPA doesn’t mean excelling, so much as it means never failing. If you’re in high school and are taking six classes, if you fail one, your GPA is now 3.3 or less, regardless of how good you are otherwise.
In any field, at the top end, you tend to get a lot of variance. (Insert tales of the mad artist and mad mathematician.) Negative selection suppresses variance, by eliminating many of the dimensions on which people vary. Students at Yale are, for the most part, all strikingly similar – same socioeconomic class, same interests, same pursuits, same life goals, even the same style of dress. A lot of people tend to assume performance follows a bell curve, but in some cases, it’s more like a Pareto distribution: the top people do hundreds or thousands of times better than average. Hence, if you eliminate the small fraction of people at the very top, your performance is hosed. Fortunately for VC funds, the startup world is still positive selection.
Less obviously, a world with lots of negative selection might be a nasty one to live in. If you think of yourself as trying to eliminate bad, rather than encourage good, you start operating on the purity vs. contamination moral axis. Any tiny amount of bad, anywhere, must be gotten rid of, and that can lead to all sorts of nastiness. “When you are a Guardian of the Truth, all you can do is try to stave off the inevitable slide into entropy by zapping anything that departs from the Truth. If there’s some way to pump against entropy, generate new true beliefs along with a little waste heat, that same pump can keep the truth alive without secret police.”
The Rationalist Conspiracy 
This seems to me to be a true observation, but the questions that it brings up to me are a) why is it so rarely brought up explicitly, and
b) what sort of cultural forces have pushed for this, and exaggerated it, with time?
In particular, to what extent does Democratic culture discourage acknowledging the large spread of right tail performance in domains where it isn’t easily measured? How many of the world’s 90th percentile and below academics would one give up rather than the one best in their field? How does this vary by field?
There seem to be two related issues here: 1) whether selection aims to avoid the worst people, or find the best, and 2) whether selection requires you to do well on a number of measures, or only one (maybe aggregate). It seems like the second characteristic is what you are concerned about, though you talk as if it is the first.
First, negative and positive selection is a false dichotomy. For example, another straightforward way to do selection is to compute some linear combination of a person’s attributes to score them, which is neither negative nor positive selection.
Second, entrepreneurship seems to me (and at least one successful entrepreneur I heard a lecture from) as a classic example of negative-type selection. To create a successful company, you have to be making a product people want, you have to get the business model right, you have to hire good people, you have to secure funding, you have to be good at acquiring customers, etc. Fail at any of these and your company is a flop.
I suspect you are confusing negative/positive selection and how forgiving a selection process is of failure. Tenure is not forgiving of failure; entrepreneurship is.
This sort of analysis can be deceptive because society is way more complicated than simple models make it out to be. For example, I expect medical residents are overworked because it so happens that hospitals profit maximize when they overwork their residents. I doubt anyone makes a deliberate effort to favor negative selection over positive selection for its own sake; they just respond to economic, cultural, political, and social forces. Yes, having mental models like this is nice, just be aware that you aren’t coming anywhere close to describing all the complexity under society’s hood.
Obviously these categories don’t have mathematical precision, there’s grey areas, etc., but I think they’re still very useful. See Paul Graham’s essay How To Do Philosophy for more on that (http://www.paulgraham.com/philosophy.html).
Entrepreneurship is not like that at all. The world is very very large, and there are a huge number of possible paths through it. It’s more like: each thing you do that works well makes your company more likely succeed, and when you do enough things well, your company is successful. But there are very few things you have to do well; there’s no checklist of things that everyone must cross off. Entrepreneurship is more like a positive selection test scored out of 100,000 points, where you need 1,000 points to pass, and the average score is 20.
The way you describe entrepreneurship isn’t forgiving of failure at all; according to that model, if you do even one thing wrong, your company is toast.
Re: models not being perfect, see http://lesswrong.com/lw/mm/the_fallacy_of_gray/, http://lesswrong.com/lw/nw/fallacies_of_compression/, http://lesswrong.com/lw/h8/tsuyoku_naritai_i_want_to_become_stronger/
http://kernull.com/bioradio.pdf “Why are modern scientists so dull? How science selects for perseverance and sociability at the expense of intelligence and creativity”
(Read it for my little essay http://www.gwern.net/Notes#conscientiousness-and-online-education )
I’m currently considering pursuing a PhD. Thank you for the first link – the more I read the more inclined I am to temper my enthusiasm with what appears to be a bleak reality.
I think negative selection is driven by fear of being blamed.
Choosing for excellence is sticking your neck out– what if you say someone is going to be excellent, and then they don’t do anything interesting?
Choosing for not having anything wrong means that you can just use common preconceptions.
Could positive/negative selection be related with knowing or not knowing what exactly you want? I mean, if you know you want X, you can select for X. But if you only have a vague idea that you want “something very good”, all you can do is filter out what you perceive as flaws, because obviously (halo effect) something with a flaw cannot be very good.
In addition to not knowing what you want, it may be a problem of not knowing how to measure what you want (either because it is generally difficult to measure, or because you specifically lack the ability to measure it), or perhaps different people having different opinions so they can’t agree on the positive goal but can still agree on many flaws.
I suspect that not knowing what you want often feels from inside as applying “holistic criteria”. So the people who don’t know what they want and instead use elimination of flaws as a proxy for a nebulous idea of goodness, might actually believe they are very smart and doing the right thing (e.g. the people doing admission exams for Harvard are probably proud about their superior methods). If your map is horribly complicated, you will congratulate yourself for your ability to navigate such complicated territory.