September 2007

Friday Random Ten: Honorable Estate Edition

Okay, not really random, nor for that matter ten. Nor even Friday, as the big event is tomorrow.

Here’s the first twenty songs of the playlist:

  1. Louis Armstrong & Duke Ellington, I’m Just a Lucky So and So
  2. Lyle Lovett, Good Intentions
  3. Al Green, I’m Glad You’re Mine
  4. Patricia Barber, Lost In This Love
  5. Emerson, Lake & Palmer, So Far to Fall
  6. Rahsaan Roland Kirk, Never Can Say Goodbye
  7. Loving Paris, Loco
  8. Parliament, Mothership Connection
  9. Yannick Noah, December 1963 (Oh, What a Night)
  10. Gary Moore, Eyesight to the Blind
  11. Maria Papadopoulou, Maskaremeni
  12. Gipsyland, Salaam
  13. Esther Phillips, Cry Me a River Blues
  14. Either/Orchestra, No Me Molesta
  15. Joe Strummer & the Mescaleros, Mondo Bongo
  16. Alihan Samedov, Sen Gelmez Oldun
  17. Cesaria Evora, Nho Antone Escaraderode
  18. Billie Holiday, Comes Love
  19. Madeliene Peyroux, Don’t Wait Too Long
  20. Living Colour, Love Rears It’s Ugly Head

We hit ’em heavy right at the beginning; once Satchmo and Duke are finished, there won’t be a dry eye in the house. A few more lovey-dovey songs to set the mood, and then the tempo ratchets up and stays there. Never Can Say Goodbye is the first of many lesser-known covers of well-known songs; it’s a nice way to mix in some familiarity without stooping to cliche. And Yannick (not Noah — see comments) has a version of December 1963 that is really too catchy to be believed. Joe Strummer tops the list with three entries in the total of eighty songs; Mondo Bongo because it’s romantic and we’re rocking the Mr. and Mrs. Smith vibe; All In a Day because there’s a line in there about “East of Chavez Ravine,” where the actual wedding is being held; and the Clash’s Death or Glory because Death or Glory is awesome.

A keen eye will detect that we haven’t limited ourselves to conventionally romantic tunes, but have allowed the occasional foray into ironic detachment; that’s okay, the relationship is like that too.

Now if you’ll excuse me, I have to go get married.

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Unsolicited Advice, IV: How to Be a Good Graduate Student

Past installments of Unsolicited Advice dealt with such mechanical topics as how to choose an undergraduate school or graduate school, or how to get into graduate school. (Hell if I know how to get into undergraduate schools.) Now we step fearlessly into somewhat more treacherous territory: how to be a good graduate student. As always, this is one idiosyncratic viewpoint, and others should be offered in the comments.

It’s treacherous, of course, because there is certainly no right way to go about being a good graduate student. Once upon a time, as part of my ongoing campaign to discredit the notion of make-or-break general exams, I had the physics department at Chicago do a survey of their faculty, asking them to give a subjective rating of all the Ph.D. students who had graduated in the last five years (and with whose work they were familiar). We then plotted the resulting scores against how well they did on the candidacy exam. Result: there was a small handful of students who completely dominated on the exam, and were pretty much recognized as excellent physicists, clustered in the corner. Other than that, a complete scatterplot — there was no correlation between test scores and success in physics (among this highly-selected sample). But if you plotted candidacy-exam scores against incoming physics GRE scores, it was almost a perfect correlation. There are some students who are the kind who are really good at physics in an exam-type environment, and who have the ability to carry through that talent to actually doing research. But there are others who struggle with the tests, yet nevertheless are great physicists. And vice-versa: you can be a crappy physicist, whether or not you do well at the GRE’s and general exams.

The point being, there are many ways to be a successful physicist, and a corresponding number of ways to be a successful grad student. So the first piece of advice, possibly too vague to be useful, is: Look to maximize your talents. Typically, your first year or two in grad school you have some flexibility. You’re taking classes (this is written from an American perspective, sorry), and possibly also doing research, but you haven’t necessarily been tied down to a final choice of thesis advisor, or even research field, or even theory vs. experiment. This would be a good time to be honest with yourself — what are you really good at? You might have had your heart set on building the next great particle accelerator ever since you deconstructed your parents’ stereo when you were twelve, but when someone puts a soldering iron in your hand you just can’t seem to stop breaking things. But you did get a perfect score on the GRE. Well, maybe it’s time to face the music and switch to string theory.

But I’m burying the lede here. If I had to concentrate on a single useful piece of advice for grad students, it would be: Take the initiative. The deep truth of grad school is that the transition from undergrad to grad is when you go from primarily being “a student” to primarily being “a scientist.” As a student, your primary responsibility was to do what your professors told you to. As a scientist, your primary responsibility is to do good science. Many students struggle in grad school, especially in the early years, because they are implicitly waiting to be told what to do. Don’t wait — try to figure out what you should be doing, and do it. Check the arxiv in the morning to look for interesting papers. Go to colloquia and seminars, even if you don’t understand them — nobody really understands them, and it’s the best way to get a feeling for what those things are that you should be working toward understanding. Talk to people! Knock on professors’ doors (or, more politely, email them to make an appointment), and chat with them about what they are doing and what you might like to be doing. Even better, talk to senior grad students and — best of all — postdocs! They have more time than professors, and have a better understanding of the situation you are in right now. (When it comes time to apply for postdocs yourself, you’re going to need three letters of recommendation from scientists who know you and your work very well. If you can only think of one or two people who might qualify, you’ve badly mismanaged your time in grad school.) Come up with ideas! A good advisor will set you on a productive path for your first research projects, but that’s no reason why you shouldn’t also be trying to come up with good ideas yourself; at some point that’s going to be your job, after all. And when it comes to the nitty-gritty of actually doing research, whether it’s theory or experiment, don’t expect anyone to hold your hand at every step — use your brain to try to figure out what should be done next. At some point you will sit back and realize that it’s kind of fun. And then it will dawn on you that you’ve passed the threshold toward which you’ve been progressing for quite a number of years — you’re an honest-to-goodness scientist.

We can’t pretend, of course, that being a scientist is just a matter of willpower; you do have to learn some stuff. One of the eternal grad-school dilemmas is how many courses you should take, vs. how quickly you should just devote yourself to doing research. I’m going to have to be wishy-washy here, as there is no right answer, although it’s certainly possible to go too far in either direction. If you dive into doing research without having a proper grounding in coursework, you can end up being an expert in the one particular hyper-specialized thing that you are researching, but be left with a rather fuzzy grasp of all the rest of physics. Not only does a situation like that doom you to a lifetime of sitting in on talks that you don’t understand, but it might prevent you from making crucial connections that would actually be useful in your own work. But contrariwise, it’s certainly possible to spend too much of your time taking classes. Classwork is what you have trained to be good at, and in some ways it’s a comforting environment. But it’s ultimately not the point of why you are in grad school. Likewise, sometimes you will really want to learn some particular subject, but your department doesn’t offer a course in it. Here’s where you should figure out that it’s your responsibility to teach it to yourself. Especially these days, when there are not only five good textbooks but countless reviews on every subject available online, there’s no excuse for waiting for a teacher to come along — see the previous paragraph.

Even once you get past courses and are unambiguously doing research, a similar dilemma presents itself — calculating vs. contemplating. (That would be the theorist’s version of the dilemma, anyway; experimenters are invited to suggest alliterative formulations of “tinkering vs. collecting data.”) Being a scientist is a back-and-forth process, between on the one hand looking at the big picture, learning the basics, thinking deeply, coming up with new ideas, and on the other hand digging into the details, getting your hands dirty, and actually coming up with some tangible results. Science depends on both, although many people are happier on one side than the other. Despite what was said earlier about finding your strengths, here’s a situation where you should make an extra effort to compensate for your weaknesses. You might be someone who loves doing calculations, producing page after page of equations, or file after file of simulation output. But if they don’t add up to an interesting result, people aren’t going to care that much. Or you might have deep and creative ideas about the nature of space and time or high-temperature superconductivity. But if you can’t wrestle those ideas down to some specific calculations, your colleagues aren’t going to be all that impressed. Sometimes, remember, the best ideas actually come about because you are simply fooling around with some calculations for their own sake.

All of this has been necessarily vague, in accordance with the fact that there are many good ways to be a successful grad student. But at the end, the goal (for most people) is pretty concrete: to land a good postdoc. Do keep that in mind. So, no matter what your individual approach to success is, here is the eyes-on-the-prize advice: Be the kind of grad student that people would like to hire as a postdoc. What kind of student is that? Well, just ask yourself what you would be looking for, if you had a pile of promising postdoc applications in front of you. Some people are lucky enough to get general-purpose fellowships that are based simply on their genius; so if the genius thing is working for you, great. More postdocs are hired by some particular person or group, to perform some fairly well-defined kind of research. What those people are looking for is a postdoc who will contribute to their group, whether by being an awesome individual researcher, or by being a useful collaborator. So, be that person. While you’re in grad school, establish a track record of productivity by writing papers. Even better, write good papers — write about things that other people are interested in. What is it about your research or skill set that makes you useful to people hiring postdocs? Become the world’s expert in some hot topic, or the master of some novel technique, along with establishing your broad-based competence. A good postdoc is expected to enliven a research group by being plugged into all the latest good stuff going on in the field, bubbling with new ideas and the energy and know-how to turn those ideas into tangible results. That should be you.

(Certainly, not everyone will become a postdoc, nor should they. One of my best students didn’t even apply for postdocs, after he determined it just wasn’t for him. There are many other directions in which to steer your career after a successful time in grad school, and it pays to keep those possibilities in the back of your mind all along. But I’m not really the one to ask about them.)

To be more concrete yet: Be a finisher. After several years of grad school, what do you have to show for it? Write papers, do analyses, build equipment, finish experiments. Demonstrate beyond any doubt that you can take the project from beginning to end, not just sit around the coffee room and lob probing questions. Give talks! Have something to say, and be confident that other people want to hear it. I’ve actually heard some students say that they love science, but don’t like writing papers or giving talks. That’s like saying you love being a butcher, just aren’t very fond of cutting up animals. (Suggestions for more illuminating similes are welcome.) Writing papers and giving talks is the entire point of what you are doing. Be enthusiastic about it, and while you’re at it, be good at it. There are so many smart people out there who write impenetrable papers or give incomprehensible talks, one good way to distinguish yourself from the herd is to learn to communicate effectively. But it won’t help unless you have something tangible to communicate.

September has long been my favorite month of the year, as campuses come to life with the incoming students, many of them starting off on a new adventure of one sort or another. Go get ’em, tiger.

Update: Many other people, of course, have offered advice on how to be a good grad student. If you know of any, mention them in the comments and I’ll link from here.

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Academics: Still Totally Lame

And Deirdre McCloskey wins the award for most ostentatious lameness. Not that I have anything really against Deirdre McCloskey; she’s an influential economist, a gifted writer, and has a compelling personal story to boot. But still.

Here’s the thing: the Chronicle of Higher Education asked a handful of academics to divulge their guilty pleasures. Seems like a potentially amusing parlor game, no? Well, as a moment’s reflection would reveal, no. Because you see, what could they possibly say? Most academics, for better or for worse, basically conform to the stereotype. They like reading books and teaching classes, not shooting up heroin or walking around in public dressed up in gender-inappropriate undergarments. (See, I don’t even know what would count as a respectable guilty pleasure.) And if they did, they certainly wouldn’t admit it. And if they did admit it, it certainly wouldn’t be in the pages of the Chronicle.

I was one of the people they asked, and I immediately felt bad that I couldn’t come up with a more salacious, or at least quirky and eccentric, guilty pleasure. I chose going to Vegas, a very unique and daring pastime that is shared by millions of people every week. I was sure that, once the roundup appeared in print, I would be shown up as the milquetoast I truly am, my pretensions to edgy hipness once again roundly flogged for the enjoyment of others.

But no. As it turns out, compared to my colleagues I’m some sort of cross between Hunter S. Thompson and Caligula. Get a load of some of these guilty pleasures: Sudoku. Riding a bike. And then, without hint of sarcasm: Landscape restoration. Gee, I hope your Mom never finds out about that.

But the award goes to Prof. McCloskey, who in a candid examination of the dark hedonistic corners of her soul, managed to include this sentence:

Nothing pleases me more than opening a new textbook.

Arrrgh! Stuff like that sets back the cause of academic non-geekiness for centuries!

The irony is, I totally know what she means.

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US/LHC Blogs

This has already been batted around a bit, but for those of you who depend on CV for absolutely all of your news, there is a new US/LHC website, brought to you by the collective US institutions involved in the Large Hadron Collider. Like any hip contemporary internet presence, it comes complete with a blog. A group blog, in fact, featuring four physicists working on different aspects of the LHC: Monica Dunford, Pamela Klabbers, Steve Nahn, and Peter Steinberg. (I thought Peter already had a blog, but apparently some people can’t be confined to just one.) It’s great that we’ll get more inside scoop about what is happening at the LHC, in addition to the awesome scoop you can already get here and elsewhere.

There has been some fretting that the LHC, scheduled to turn on next year, is already getting too much hype. On the list of my own personal worries, this does not crack the top million. If you’re someone who reads several physics blogs and scans the Science Times and the wire services for stories about particle physics, you may have been subjected to a lot of stories about an experiment that hasn’t yet collected any data. But the more casual reader is very far from reaching a point of LHC over-exposure. This is by far the most important experiment in the last thirty years in an undeniably significant subfield of physics. The excitement is perfectly justified, and there will be much more to come.

ATLAS cavern

The ATLAS cavern. Those poor particles won’t know what hit them!

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Disinviting Larry

Larry Summers is an extremely smart guy who said some extremely stupid things about women and science at a conference. For this and many other reasons (mostly “other,” but it’s a messy story), he lost the confidence of Harvard’s faculty and eventually resigned. And good riddance; for all of his talents and all the good he did for Harvard, he caused more harm by antagonizing people and generally playing the autocrat when the office of university president calls for something more subtle.

Which doesn’t mean that he should be banned in perpetuity from giving talks to university audiences. A recent invitation from the University of California Regents has been rescinded after a group of UC faculty circulated a petition demanding that Summers be disinvited. Whether or not you had any sympathy for what Summers said at the NBER conference (I certainly don’t), he is a serious academic, and should be accorded the usual protections for saying what he thinks. Bitch PhD is wondering about the situation, and here’s the comment I left at her blog:

I think the disinvitation was a bad idea, on substantive grounds as well as for the bad image it projects.

For one thing, the proposition that innate differences play a large role in determining the distribution of genders (and races) throughout academia is certainly controversial — it’s not just a matter of scholarly vs. otherwise. There are smart and well-informed people who believe that innate differences are the most important thing suppressing the number of women in science; Stephen Pinker is an obvious example. I personally think those people are crazy and wrong, but won’t deny that they are smart and well-informed.

Second and more importantly, it’s just wrong to think of Summers as symbolizing prejudice. Although there are smart and well-informed prejudiced people per above, Summers was certainly not well-informed when he made his comments at the NBER conference. He has since apologized profusely and allocated millions of dollars toward making things better. It all may be perfectly insincere, but when there are plenty of actual sexists out there who are willing to defend such positions even when they are well-informed, it seems like a mistake to hold that the only possible role Larry Summers can play is buffoonish sexist. He does have other things on his CV.

Finally, I haven’t seen any evidence that Summers was actually invited to talk about gender or science or anything like that. If he were, that would be evidence of rank stupidity (of which the Regents are of course well-known masters).

Among the “image” problems alluded to above, stuff likes this makes it possible for conservatives to beat the drum of leftist intolerance of other people’s views. Ironically, the incident comes on the same week of a much more serious violation of academic freedom: UC Irvine’s withdrawal of a the offer of the job of Dean at its brand new law school, to Duke constitutional scholar Erwin Chemerinsky. That act, which has apparently been reversed so that Chemerinsky can in fact be the Dean, resulted from right-wing pressure against a professor who they thought was too liberal. Becoming the Dean is a noticeably bigger deal than giving a dinner-time talk to the UC Regents. Nevertheless, the Summers flap has given conservatives the chance to argue that “the primary challenge facing academic freedom in American universities” is “the rise of an academic far-left establishment that seeks to use universities as a base for political activism, and is perfectly willing to violate accepted standards of academic freedom to achieve that goal.” And they’ve taken it!

Well, if we go around disinviting speakers because we disagree with their views, we deserve what we get. In the wake of Summers’s original speech, there was much heat, but also a good deal of light — data and arguments were produced that showed to any reasonable person that women interested in science face extraordinary amounts of discrimination at all steps of the process. Let’s stick with the “data and arguments” approach.

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Play Guess-the-Histogram

Charts and graphs are always exciting. They add an undeniable aura of quantification to any set of claims. What I like to do, when I see a graph illustrating some news item, is to guess what is being plotted before reading the text or axes labels very carefully. Here, via Ezra Klein, are the results of a BBC/ABC News poll:

Iraqis polled on surge

The large-type words at the top give away the basic issue being addressed: has the U.S. “surge” of additional forces into the Baghdad area made things better or worse? But you can still get the picture from glancing at the colorful vertical bars, before reading any of the tiny text. Tiny red and yellow outliers flank a rampant baby-blue cohort. So my guess was, red meant “better,” blue meant “stayed the same,” while yellow meant “worse.” That would reflect what I had been hearing in the wake of Gen. David Petraeus’s testimony before Congress, that overall Americans were not in the slightest convinced that the escalation was bringing an end to sectarian and helping to nuture the first flowerings of Iraqi participatory democracy, with checks and balances for all.

But no! A glance at the fine print reveals that it was blue that corresponded to “worse,” while yellow meant “had no effect.” (In my defense, why wasn’t “had no effect” put in the middle?) I knew the war and the surge were unpopular, but had no idea they were that unpopular.

It takes a dip into the text in the article accompanying the graph to figure out what is going on: this was a poll of Iraqis, not Americans. So now it all makes sense; as unpopular as our military efforts are here at home, it’s nothing like the scorn that we receive from the country we are purportedly saving. Admittedly, closer scrutiny did provide clues that the poll might not have been sampling Americans: the question referred specifically to the escalation “in Baghdad and surrounding provinces,” rather than just “in Iraq,” a distinction that is rather too fine for most Americans to fret about. And there were six different forms of the question, addressing levels of detail that again would not be foremost of the minds of anyone who saw things in terms of supporting vs. attacking our brave men and women in uniform. Like the President.

The best argument for leaving Iraq is that the Iraqis don’t want us there. (It’s not an argument that is discussed very much, for reasons about which you are free to speculate.) This poll from earlier this year is illuminating. On the basic issue of “Do you support the presence of Coalition forces in Iraq?” we find that 46% strongly oppose and 32% somewhat oppose, with only 22% support, strongly or otherwise. It’s not completely unambiguous; when asked if those selfsame forces should get up and leave, only 35% just say “leave now” — which you will notice is smaller than the number who strongly oppose their presence. A full 63% want the forces to stay until they achieve some goal of improving the political or security situation, even though they are not judged to be doing a very good job at that. (The numbers might look worse, post-surge.) Which goes to show that Iraqis don’t necessarily think any more clearly about these things than Americans do.

Of course, only 1% of Iraqis want American forces to stay forever, which is what our government has been preparing to do. So someone is going to end up being disappointed.

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Bacon-Flavored Chocolate

I thought Atrios was kidding, but no. Vosges Haut Chocolat has indeed come out with a bacon-flavored chocolate bar. I’m not sure if it qualifies as long-awaited, but it should have been.

Vosges Bacon Chocolate

From the description:

Bacon Exotic Candy Bar – New

Applewood smoked bacon + Alder smoked salt + deep milk chocolate

Deep milk chocolate coats your mouth and leads to the crunch of smoked bacon pieces. Surprise your mouth with the smoked salt and sweet milk chocolate combination.

Crisp, buttery, compulsively irresistible bacon and milk chocolate combination has long been a favorite of mine. I started playing with this combination at the tender age of six while eating chocolate chip pancakes drenched in maple syrup. Beside my chocolate-laden cakes laid three strips of fried bacon, just barely touching a sweet pool of maple syrup. Just a bite of the bacon was too salty and yearned for the sweet kiss of chocolate syrup. In retrospect, perhaps this was a turning point, for on that plate something magical happened: the beginnings of a combination so ethereal and delicious that it would haunt my thoughts until I found the medium to express it–chocolate.
–Katrina

Vosges is my favorite chocolatier (if you know what I mean). Not only do they blend excellent chocolate with a wide variety of exotic spices to create uniformly interesting and delicious combinations, but I stumbled upon them when they were just a tiny one-shop operation in Chicago, before their blossoming into international success. And a friend of mine once claimed that every type of food is enhanced by the addition of bacon, including ice cream. (Although I did manage to give her pause with my suggestion of bacon-flavored water.) So I’m thinking I’m going to have to give the new experiment a try. You only live once.

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Rationality Revisited

Speaking about how someone with a physics background might approach economics, you might prefer intimidatingly-informed commentary over my unfettered-by-knowledge noodling. In that case, you should zip over to Cosma Shalizi’s blog, where he offers a thoroughly-hyperlinked meditation on the state of econophysics. Full of good stuff along the lines of:

So then: why oh why don’t we have better econophysics?

The first reason which occurs to me, now that I’m a dues-paying, card-carrying statistician, is that almost all econophysicists are theoretical physicists, and moreover statistical physicists. (I’m one myself, or at least was through my Ph.D.) Modern physics began, in the 17th century, by fusing mathematical
theorizing
and artisanal craft, but one result of our progress has been to impose a specialized division of labor, sharply separating theory and experiment; Fermi was probably the last physicist to be both a great theorist and a great experimenter. (Perhaps this is connected to his invention of Monte Carlo?) This means that it is very rare for a theoretical physicist to analyze actual empirical data (say, measurements of magnetic susceptibility), which is what the experimentalists do. Theorists instead deal with experimental results (say, that the susceptibility depends on temperature in such-and-such a way). In high energy physics, theorists are actually so remote from contact with experimentalists that a separate guild of interface specialists (“phenomenologists”) has arisen to mediate between them. As a natural consequence of this division of labor, theorists receive no instruction at all in data analysis, let alone statistical inference.

There is much more. Jim Cronin once loaned me some videotapes of old news shows from the 1940’s that featured interviews with Enrico Fermi. He was an amazing guy, the kind who would kill time on a free afternoon by coming up with an explanation for the origin of cosmic rays. It’s too bad that, in the popular or semi-popular imagination, his name doesn’t immediately pop up on the list of the demigods of 20th-century physics. You could make a solid case that he should be number two after Einstein.

Crooked Timber links to Cosma’s post, and also features a post by John Quiggin that follows up on mine. He notes that most of my suggestions are well-incorporated into economics, which is no surprise. The part that is judged interesting is the idea that social scientists would be well-served to distinguish between descriptive notions of what people do and prescriptive notions of what is considered “rational.” A blog at The Economist (the magazine they like to call a newspaper) makes a similar point, so maybe there is something there. Indeed, we are informed that this kind of reasoning keeps popping up despite the fact that Joseph Butler demolished it 300 years ago, so there must be something attractive about it. (Hey, David Hume demolished the argument from design before William Paley even popularized it, but you don’t see it fading away, do you?)

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So What Have You Been Maximizing Lately?

A while back, Brad DeLong referred to Ezra Klein’s review of Tyler Cowen’s book Discover Your Inner Economist. (Which I own but haven’t yet read; if it’s as interesting as the blog, I’m sure it will be great.) The question involves rational action in the face of substantial mark-ups on the price of wine in nice restaurants:

I did once try to convince Bob Hall at a restaurant in Palo Alto not to order wine: the fact that the wine would cost four times retail would, I said, depress me and lower my utility. Even though I wasn’t paying for it, I would still feel as though I was being cheated, and as I drank the wine that would depress me more than the wine would please me.

He had two responses: (i) “You really are crazy.” (ii) “Think, instead, that it’s coming straight out of the Hoover Institution endowment, and order two bottles.”

He is crazy, of course — crazy like an economist. I left a searingly brilliant riposte in the comment section of the post, which mysteriously never appeared. He will probably claim it was a software glitch or that I hit “Preview” instead of hitting “Post,” but I know better. What are you afraid of, Brad DeLong!?

Economists have a certain way of looking at the world, in which (to simplify quite a bit) people act rationally to maximize their utility. That sort of talk pushes physicists’ buttons, because maximizing functions is something we do all the time. I’m not deeply familiar with economics in any sense; everything I know about the subject comes from reading blogs. Any social science is much harder than physics, in the sense that constructing quantitative models that usefully describe the behavior of realistic systems is made enormously difficult by the inherent nonlinearities of human interactions. (“Ignoring friction” is the basis of 98% of physics, but nearly impossible in social sciences.) But I can’t help speculating, in a completely uninformed way, how economists could improve their modeling of human behavior. Anyone who actually knows something about economics is welcome to chime in to explain why all this is crazy (very possible), or perfectly well-known to all working economists (more likely), or good stuff that they will steal for their next paper (least likely). The freedom to speculate is what blogs are all about.

Utility is a map from the space of goods (or some space of outcomes) to the real numbers:

U: {goods} -> R

The utility function encapsulates preferences by measuring how happy I would be if I had those goods. If a set of goods A brings me greater utility than a set B, and I have to choose between them, it would be rational for me to choose A. Seems reasonable. But a number of issues arise when we put this kind of philosophy into practice. So here are those that occur to me, over the course of one plane ride across a couple of time zones.

  • Utility is non-linear.

This one is so perfectly obvious that I’m sure everyone knows it; nevertheless, it’s what immediately popped into mind upon reading the wine story. We need to distinguish between two different senses of linear. One is that increasing the amount of goods leads to a proportional increase in utility: U(ax) = aU(x), where x is some collection of goods and a is a real number. Everyone really does know better than that; the notion of marginal utility captures the fact that eating five deep-fried sliders does not bring you five times the happiness that eating just one would bring you. (Likely it brings you less.)

But the other, closely related, sense of linearity is the ability to simply add together the utility associated with different kinds of goods: U(x+y) = U(x) + U(y), where x and y are different goods. In the real world, utility isn’t anything like that. It’s highly nonlinear; the presence of one good can dramatically affect the value placed on another one. I’m also pretty sure that absolutely every economist in the world must know this, and surely they use interesting non-linear utility functions when they write their microeconomics papers. But the temptation to approximate things as linear can lead, I suspect, to the kind of faulty reasoning that dissuades you from ordering wine in nice restaurants. Of course, you could have water with your meal, and then go home and have a glass of wine you bought yourself, thereby saving some money and presumably increasing your net utility. But having wine with dinner is simply a different experience than having the wine later, after you’ve returned home. There is, a physicist would say, strong coupling between the food, the wine, the atmosphere, and other aspects of the dining experience. And paying for that coupling might very well be worth it.

Physicists deal with this by working hard at isolating the correct set of variables which are (relatively) weakly-coupled, and dealing with the dynamics of those variables. It would be silly, for example, to worry about protons and neutrons if you were trying to understand chemistry — atoms and electrons are all you need. So the question is, is there an economic equivalent to the idea of an effective field theory?

  • Utility is not a function of goods.

Another in the category of “surely all the economists in the world know this, but they don’t always act that way.” A classic (if tongue-in-cheek) example is provided by this proposal to cure the economic inefficiency of Halloween by giving out money instead of candy. After all, chances are small that the candy you collect will align perfectly with the candy you would most like to have. The logical conclusion of such reasoning is that nobody should ever buy a gift for anyone else; the recipient, knowing their own preferences, could always purchase equal or greater utility if they were just given the money directly.

But there is an intrinsic utility in gift-giving; we value a certain object for having received it on a special occasion from a loved one (or from a stranger while trick-or-treating), in addition to its inherent value. Now, one can try to account for this effect by introducing “having been given as a gift” as a kind of good in its own right, but that’s clearly a stopgap. Instead, it makes sense to expand the domain set on which the utility function is defined. For example, in addition to a set of goods, we include information about the path by which those goods came to us. Path-dependent utility could easily account for the difference between being given a meaningful gift and being handed the money to buy the same item ourselves. Best of all, there are clearly a number of fascinating technical problems to be solved concerning strategies for maximizing path-dependent utility. (Could we, for example, usefully approximate the space of paths by restricting attention to the tangent bundle of the space of goods?) Full employment for mathematical economists! Other interesting variables that could be added to the domain set on which utility is defined are left as exercises for the reader.

  • People do not behave rationally.

This is the first objection everyone thinks of when they hear about rational-choice theory — rational behavior is a rare, precious subset of all human activity, not the norm that we should simply expect. And again, economists are perfectly aware of this, and incorporating “irrationality” into their models seems to be a growth business.

But I’d like to argue something a bit different — not simply that people don’t behave rationally, but that “rational” and “irrational” aren’t necessarily useful terms in which to think about behavior. After all, any kind of deterministic behavior — faced with equivalent circumstances, a certain person will always act the same way — can be modeled as the maximization of some function. But it might not be helpful to think of that function as utility, or as the act of maximizing it as the manifestation of rationality. If the job of science is to describe what happens in the world, then there is an empirical question about what function people go around maximizing, and figuring out that function is the beginning and end of our job. Slipping words like “rational” in there creates an impression, intentional or not, that maximizing utility is what we should be doing — a prescriptive claim rather than a descriptive one. It may, as a conceptually distinct issue, be a good thing to act in this particular way; but that’s a question of moral philosophy, not of economics.

  • People don’t even behave deterministically.

If, given a set of goods (or circumstances more generally), a certain person will always act in a certain way, we can always describe such behavior as maximizing a function. But real people don’t act that way. At least, I know I don’t — when faced with a tough choice, I might go a certain way, but I can’t guarantee that I would always do the same thing if I were faced with the identical choice another hundred times. It may be that I would be a lot more deterministic if I knew everything about my microstate — the exact configuration of every neuron and chemical transmitter in my brain, if not every atom and photon — but I certainly don’t. There is an inherent randomness in decision-making, which we can choose to ascribe to the coarse-grained description that we necessarily use in talking about realistic situations, but is there one way or the other.

The upshot of which is, a full description of behavior needs to be cast not simply in terms of the most function-maximizing choice, but in a probability distribution over different choices. The evolution of such a distribution would be essentially governed by the same function (utility or whatever) that purportedly governs deterministic behavior, in the same way that the dynamics in Boltzmann’s equation is ultimately governed by Newton’s laws. The fun part is, you’d be making better use of the whole utility function, not just those special points at which it is maximized — just like the Feynman path integral established a way to make use of the entire classical action, not just those extremal points. I have no idea whether thinking in this way would be useful for addressing any real-world problems, but at the very least it should provide full employment for mathematical economists.

Okay, I bet that’s at least three or four Sveriges Riksbank Prizes in Economic Sciences in Memory of Alfred Nobel lurking in there somewhere. Get working, people!

So What Have You Been Maximizing Lately? Read More »

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Facing the Future

We now have a Facebook group for Cosmic Variance! But let me work up to it.

I had heard about Facebook many times, but had effortlessly resisted the temptation to learn anything about it or get involved in any way. It’s a social-networking site, allowing people to keep each other up to date with stuff they are doing. A pastime in which I pretty much have no interest, despite what one might gather from the fact that I have a blog and all that. While I’ll tell stories about travel or amusing anecdotes for purposes of local color, and mention the occasional big event, for the most part I prefer to use the blog to talk about ideas and keep the fascinating details of my everyday life a tightly-shrouded mystery.

But at some point, the “everyone is doing it, how hard can it be, and maybe it could even be fun” argument kicks in, and in a moment of weakness you sign up. I blame Carl Zimmer, who just joined himself, with the usual disclaimers. It’s free, and easy as pie — you sign up, post a photo if you like, and that’s it.

The basic point of Facebook, according to my limited understanding, is to have “Friends.” That is, a set of other Facebookers with whom you have (mutually) agreed to allow access to your profile and information. There is a quite brilliant application via which, if you choose to allow it, Facebook can zip through a conventional email program (Gmail, apple, etc) looking for email addresses of other people with Facebook accounts, and let you ask them to be friends. And then there are networks of common interest and all that stuff. The obvious use is that you can simply tell Facebook when you’ve decided to quit your job and hike across the Andes, rather than emailing all of your friends individually.

But there is a deep problem of postmodern community ethics here — who is a “Friend,” in the official Facebook sense? One group would be, you know, your actual friends. Another would be people with whom you have some less tangible, but nevertheless pretty mutual and well-defined, relationship — maybe you’ve exchanged emails, or comments on each others blogs. It’s all up to you where to draw the line.

But personally, I wouldn’t count someone as a “Friend” if I had simply read their book, or visited their blog, or listened to their radio show, without them knowing me at all. And vice-versa. I mean, I think — to be honest, I’m new at this, and have no idea what the standards are. It might be very natural, for example, for regular CV readers to want to be my friend, but I’m not really sure it fits my notion of what friendship is really all about.

Then I noticed that Crooked Timber has its own Facebook group. Which seemed, at first, like the dumbest thing in the world — why do you need some proprietary social network when you already have the damn blog?

Upon digging deeper, however, I realized it was actually the smartest thing in the world. (A very fine line.) With the Facebook group, people can come together and share pictures, or relevant stories or rants, without being “friends” and dealing with constant updates about what they all had for dinner last night. (Although advancing to friendship — or more! — is always possible.) And in fact there are lots of blogs that have their own Facebook group.

So, now, so do we. Go ahead and join up. Upload your photo (or not). Share videos and pictures from the regular “Fans of CV” get-togethers which I’m sure happen all the time. The Pharyngula group has over a hundred members — you don’t want to be shown up by a bunch of godless cephalophiles, do you?

But there’s no way I’m ever having a MySpace page.

Update: Seems to be working! Over a hundred members, and the irrepressible Mark Jackson has even started a conversation about physics-related movie titles.

Facing the Future Read More »

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