So many! Just a few that come to mind: compound interest, observation selection effect, bias, differential technological development, function, present value, correlation, subjective experience, trivial inconvenience, self-amplifying capacity, expectation, etc.
Also, many conceptual distinctions in philosophy are useful: analytic-synthetic, a priori-a posteriori, de re-de dicto, phenomenal-intentional, proximate-ultimate, intrinsic-instrumental, factual-normative, contingent-necessary, etc. Taxonomies of views in a given field, too, can be quite helpful in conceptualizing the relevant boundaries (e.g. Chalmers on views about consciousness or Miller on views in metaethics).
I guess one could say the concept of a useful concept is itself quite useful.
Some perhaps-too-obvious ones: comparative advantage, arbitrage, Schelling point, plurality, transfer (in education), deliberate practice, tacit knowledge.
Most functions are not linear. This may seem too obvious to be worth mentioning, but it's very easy to assume that various functions that appear in real life are linear, e.g. to assume that if a little of something is good, then more of it is better, or if a little of something is bad, then more of it is even worse (apparently some people use the term "linear fallacy" for something like this assumption), or conversely in either case.
Nonlinearity is responsible for local optima that aren't global optima, which makes optimization a difficult task in general: it's not enough just to look at the direction in which you can improve the most by changing things a little (gradient ascent), but sometimes you might need to traverse an uncanny valley and change things a lot to get to a better local optimum, e.g. if you're at a point in your life where you've made all of the small improvements you can, you may need to do something drastic like quit your job and find a better one, which will temporarily make your life worse, in order to eventually make your life even better.
The reason variance in financial investments matters, even if you only care about expected utility, is that uti...
I never really consciously thought about the idea of status until I came across it in this forum. It helped me identify and understand some behaviors in myself and others which puzzled me before.
I'm pretty sure the idea has been around since long before Robin Hanson started writing about it.
The idea of talking about seeing status signaling everywhere is characteristically Hanson. I would not be surprised in the least if many smart politicians and socialites throughout history had also observed this but had the good sense not to talk about it in public.
From off site:
Energy and Focus is more scarce than Time (at least for me), Be Specific (somewhat on site, but whatever),
From on the site:
Mind Projection Fallacy, Illusion of Transparency, Trivial Inconveniences, Goals vs. Roles, Goals vs. Urges
Extracting examples from some of my past comments: proving too much, selection bias, Nash equilibrium, denotation & connotation, insight & intuition as recognition.
Others from game theory & economics: free riders & hold outs, the tragedies of the commons & the anticommons, precommitment, coordination games, average-marginal confusion, thinking at the margin.
Two more that're a bit Sequences-esque but which I like so much and use so often I'll highlight them anyway:
Reference class forecasting. It doesn't just help one beat the planning fallacy by predicting durations; it can predict probabilities too, and one can apply it to other people as well. Will a flaky friend show up to a meal? Run a reference class forecast. Am I likely to get a "yes" if I ask someone for such & such a favour? Run a reference class forecast. How likely is it that a claim an acquaintance has just made is true? You get the idea. (Guess I should throw in reference class tennis as well. Fortunately, just as with actual tennis, it's hard to play reference class tennis on my own, so reference class tennis isn't too big a risk when I do solo reference class forecasts.)
The typica
Credibility also can be useful. Most importantly: Are the threats, precommitments and offers you make credible? Could and would you actually go through with them if you found yourself in a situation where the conditions you stated are fulfilled? If you arrange the exchange in such a way that acting on your words imposes a low cost (better yet: no cost) on yourself, you'll gain lots of bargaining power.
A quick example: When educating children, misbehaviour has to have consequences. Now, you have to choose these punishments in such a way that they impose little organizational and emotional cost on yourself while being serious enough that kids want to avoid them (but, of course, also not too serious ;)). If done correctly, you'll have to punish a few children a few times, but then they will have learned. If done incorrectly, you continuously threaten with punishment, but there is no clear line where you have to act, and put in such a situation you don't even want to punish them, so the children will continue to misbehave.
Unfortunately, this quick example is something that teachers and school administration often don't get. If you make a threat for misbehavior, you must follow through, otherwise you have seriously undermined your and every other teacher's credibility, and then you will predictably get misbehavior on almost every lesson since now.
Unfortunately, the reality is often that teachers make empty threats, hoping that using big words will scare students, and when this does not work, they rationalize not following through by "they are just children" and "they need to get a second chance", although some students already had literally hundreds of "second" chances. And the worst thing is when teacher insists on the punishment, but after a phone call from parent, the school administration overrides their decision. Of course students share their "success stories", so the next day the whole school know about the winning strategy.
Unfortunately, this quick example is something that teachers and school administration often don't get.
It is possible that their target audience is their superiors, not the students. Threat is cheap, punishment is expensive, and they can always report to their superiors (and possibly parents) "we do not condone this behavior, see, we threatened them with ".
The justice system of the old Soviet Union had, rather ironically, the following maxim:
Inevitability of punishment is more effective than its severity
From an article about the US justice system, but the relevance to misbehaving schoolchildren (or simply schoolchildren whose behaviour one doesn't like) is obvious:
Cesare Beccaria—the Italian criminologist from whom Jeremy Bentham borrowed not only the term “utility” but many of his ideas for criminal-justice reform—identified three characteristics that determine the deterrent efficacy of a threatened punishment: its swiftness, its certainty, and its severity. Of the three, severity is least important. If punishment is swift and certain, it need not be severe to be efficacious. If punishment is uncertain and delayed, it will not be efficacious even if it is severe. (It was only two and a half centuries after Beccaria that psychologists and behavioral economists discovered that some degree of excessive present-orientation, and excessive discounting of the risk of large losses, is normal.) The sort of bad gamble represented by most offenses tends to attract precisely those whose departures from rationality are most egregious.
[...]
Not only is severity an inadequate substitute for swiftness and certainty, it actually interferes with them. The more severe a punishment is, the more due process (leading to delay) is required to impose it, and (if severity is measured in sentence length) the less often it can be imposed before the prisons fill up.
eterrent efficacy of a threatened punishment: its swiftness, its certainty, and its severity.
Interestingly, these correspond to delay, expectancy and value in the procrastination equation. It's interesting to see "negative" values used to form a kind of anti-motivation.
The concept of privilege of the "check your..." variety. It's not without it's problems as a tool - it can too easily be used as a Fully General Counterargument - but it's an important thing to be aware of and probably the single concept I've learned in the last two years that has most changed my outlook on the world.
Robin Hanson's marginal charity has been quite useful for me.
Especially, when I use it for doing marginal charity towards myself. Example: I'm eating a slice of cake. The difference in utility for me between eating 3/4ths of it and all of it is small. So if I leave a 1/4th of it for future-me, the difference in utility for future-me is much larger since it is the difference between having no cake and having some cake.
Various bits from Dennett: cranes versus skyhooks, the Cartesian Theatre, 'figment', the intentional stance, the notion of an intuition pump.
Braitenberg's Vehicles does something indescribably non-verbal. It's a tiny book that passes through your mind silently, like a ninja, and then any lingering shreds of vitalism you have just sort of explode and blow away on the wind. Every child should have a copy (and robot parts to use it with).
Cost of delay. If you have two projects which when finished will generate (say) the same amount of value per time and it takes 2 weeks to do the first and 1 week to do the second, by sequencing them in the other order you gain 1 weeks' worth of value. If instead you interleave them, working "in parallel", with no real gains in total time, you lose 1 weeks' worth of value. Also and more obviously, if one project generates way more value per time, finish it first. If a project loses value while not finished, consider finishing it first. (for example taking an idea to market - your market research undergoes depreciation)
The tradeoff between efficiency and accuracy. It's essential for computational modeling, but it also comes up constantly in my daily life. It keeps me from being so much of a perfectionist that I never finish anything, for instance.
It's not so much a way to understand the world as it is a deep engineering principle. You want to design systems in such a way that if there is a problem, the system fails sooner rather than later. One very counter-intuitive technique used in software engineering is the assertion, which has no effect other than to shut the system down if a certain expression evaluates to false. Naively, it seems crazy that we would ever want to add to the set of conditions that will cause a crash - but that is exactly the point.
Failfast is part of the more general strategy expressed by the slogan tighten your feedback loops. If you are doing something stupid, you want to know as soon as possible. This is hard for humans to do, since we have a natural aversion to bad news and discipline.
Moral Foundations theory (all moral rules in all human cultures appeal to the six moral foundations: care/harm, fairness/cheating, liberty/oppression,loyalty/betrayal, authority/subversion, sanctity/degradation). This makes other people's moralities easier to understand, and is an interesting lens through which to examine your own.
The Big Five Personality Traits - though I've heard these don't seem to fit non-Westerners very well. Probably still useful when thinking about Westerners. (For example, when evaluating someone as a romantic partner or a business...
[META]
I suggest moving “repository” threads to Main, because they are threads where it would still make sense to add new entries arbitrarily long after they are originally posted, and ISTM that new comments in old threads are more likely to be noticed in Main than in Discussion.
Supervenience. For example, "the mind supervenes on the brain." The idea here is that a mind cannot be different without the corresponding brain being different as well.
I have a list of ~500 concepts / "patterns in reality" that I think it would be useful to have "handles" to, by having words/phrases for them or just having them as mentally-cached concepts. (Once I started actively looking for such concepts I found quite a lot of them.) I'm planning to someday-soon sit down and actually make up words/phrases for each of these; I've made up words/phrases for 37 of them, and my notes-to-self are already peppered with them. Unfortunately I don't have the time right now to put them all here, but I probably...
Someone put together a nice list of concepts based on Charlie Munger's "mental models"
tangent: System 1 seems to control how "profound", and thus likely-to-apply-in-the-future, any given concept feels. Venkatesh Rao has written a piece on this I can't find right now, but the gist was that we glom onto concepts that allow more efficient mental organization. For example discovering that two phenomenon we thought were separate are actually sub-cases of some more basic phenomenon. An important point is that we do this speciously, as our pattern recognition is overactive (it is worth false alarms when checking for leopards). This pred...
My personal "interesting concepts repository" lists are probably grossly inappropriate to post here, since they've got thousands of entries, and they're not accumulated systematically or sorted well or even specifically selected for usefulness. In fact many entries might even be anti-useful if examined uncritically, since they were saved as reminders that "a lot of people think/thought X" despite not satisfying "I think X". I'm also hesitant to post the lists on the web for that latter reason; who knows what idiot in HR migh...
Learning about Neurobiology. I found the more I know about how the brain works, the more cognitive science makes sense.
People assume memories are stored in one region of the brain. From the inside, it feels like all this knowledge is obviously coming from one place. Factual information about an elephant (weight, where it lives, etc) is related the mental image of an elephant (gray skin, has big ears and a trunk,) but brains store that information in completely different places.
Ah, conceptual gardening. Meta, the fourth wall, diagonalization, God, Tathāgata/Tathāgatagarbha. Optimization, credit assignment, signal/noise. Marginalization, opportunity cost, comparative advantage. Incentive, affordance, salience, Schelling point. Likelihood ratio. Compilers/universality. Reversibility). Measure, decision-theoretic-significance/policy-relevance, justification. Levels of organization, levels of abstraction, level-crossing. Logos, Platospace. Pattern attractors, emergence, teleology. Timefulness/timelessness, self-fulfilling prophecy, s...
Meta happens when we go from talking about X, to talking about talking about X. Some examples:
"Meta" is also used to mean "at a higher level of organization". For instance, if there is a competitive game G, then the metagame of G is the interaction of different styles of play in a given pool of players.
See also: Boring Advice Repository, Solved Problems Repository, Grad Student Advice Repository
I often find that my understanding of the world is strongly informed by a few key concepts. For example, I've repeatedly found the concept of opportunity cost to be a useful frame. My previous post on privileging the question is in some sense about the opportunity cost of paying attention to certain kinds of questions (namely that you don't get to use that attention on other kinds of questions). Efficient charity can also be thought of in terms of the opportunity cost of donating inefficiently to charity. I've also found the concept of incentive structure very useful for thinking about the behavior of groups of people in aggregate (see perverse incentive).
I'd like people to use this thread to post examples of concepts they've found particularly useful for understanding the world. I'm personally more interested in concepts that don't come from the Sequences, but comments describing a concept from the Sequences and explaining why you've found it useful may help people new to the Sequences. ("Useful" should be interpreted broadly: a concept specific to a particular field might be useful more generally as a metaphor.)