Posted by crshalizi at March 22, 2007 17:46 |
| permanent link
Today's find, via Mind Hacks, is an online archive at UCSD dedicated to the memory of the great Soviet neuropsychologist Alexander R. Luria. (Lots of the links are broken, though.)
Today Luria's probably best known for the "neurographies" he wrote, like The Mind of a Mnemonist and The Man with a Shattered World, which inspired Oliver Sacks's famous ventures in this line. But he actually made really important scientific contributions, which deserve to be remembered.
Luria began his career as a disciple of Lev Vygotsky, who had a fascinating pre-cognitive theory of how individuals acquire higher mental functions through a scaffolding provided by cultural traditions (especially language) and social interaction. Vygotskyism was an explicitly Marxist theory: it was supposed to be a scientific account of how thought arises from practice. While it is very hard to accept some of Vygotsky's more extreme statements, there is I think a core of very real insight here, about both individual development and collective cognition, and one which moreover is fundamentally compatible with sound computational views of the mind.
To support the theory, Luria led an expedition to Uzbekistan which sought to document how the Soviet introduction of modern education and collective agriculture (!) was transforming the mentality of the natives. The resulting report — translated as Cognitive Development: Its Cultural and Social Foundations — is an astonishing mixture of fascinating experiments and conjectures, and equally fascinating displays of colonialist blindness. Most of Luria's subjects were Uzbekistani peasants who'd been forced onto collective farms a few years earlier; a decade previously the whole province was the scene of the basmachi revolt, which was suppressed by the Red Army with the usual measures. It never crossed Luria's mind, so far as I can tell, that a bunch of Russian academics, asking questions which clearly indicated that the Russians thought the Uzbeks were idiots, would meet with anything less than full and sincere cooperation. Consider the following dialogue (p. 112) with an illiterate peasant named Nazir-Said:
The following syllogism is presented: There are no camels in Germany. The city of B. is in Germany. Are there camels there or not?Luria's interpretation was that Nazir-Said had difficulty with hypothetical syllogistic reasoning, as opposed to more concrete inferences in practical situations, difficulties typical of those "whose cognitive activity was formed by experience and not by systematic instruction or more complex forms of communication" (p. 115). But it's also easy to interpret this as Nazir-Said parrying the question with a perfectly valid, if enthymemic, syllogism ("Every large city has camels; B. is a large city; therefore B. has camels"), and then supporting his major premise with another valid syllogism ("Every large city has Kazakhs or Kirghiz; Kazakhs and Kirghiz always have camels; therefore every large city has camels"). The greater success of members of collective farms in "solving" the syllogisms might just reflect their greater willingness to cooperate with the Russians. In other words, there is a whole layer of issues here, involving the social relations between the scientists and their subjects, to which Luria turned a blind eye...
Subject repeats syllogism exactly.
So, are there camels in Germany?
"I don't know, I've never seen German villages."
Refusal to infer.
The syllogism is repeated.
"Probably there are camels there."
Repeat what I said.
"There are no camels in Germany, are there camels in B. or not? So probably there are. If it's a large city, there should be camels there."
Syllogism breaks down, inference drawn apart from its conditions.
But what do my words suggest?
"Probably there are. Since there are large cities, there should be camels."
Again a conclusion apart from the syllogism.
But if there aren't any in all of Germany?
"If it's a large city, there will be Kazakhs or Kirghiz there."
But I'm saying that there are no camels in Germany, and this city is in Germany.
"If this village is in a large city, there is probably no room for camels."
Even in Russian, this book wasn't published until 1974. One reason, to which Luria and his translators allude, was the political sensitivity of saying that Central Asians had a child-like mentality, even if that was being transformed by socialist labor. The other, though, on which they are conspicuously silent, was the well-known fact that a crude Pavlovian behaviorism became the Official Soviet Line in psychology. Vygotsky was in a sense lucky to die of tuberculosis then, rather than be purged, and Luria had to lie low in an institute for retarded children. (An old New York Review piece on Luria goes into some of the history.) Luria's memoirs, written in the 1970s, are, let us say, extremely tactful about this turn of events. His American discipline Michael Cole, in an epilogue to those memoirs, is rather more open these matters, and confesses to finding some of what Luria wrote when, as it were, he was compelled to speak Pavlovian "unnerving". What I find unnerving is that none of this seems to have turned him against the Soviet system.
In any case, this forced switch in research ultimately led Luria, during and after the war, to rehabilitation work with soldiers with brain injuries, and so to neuropsychology, where he made his greatest contributions. His academic works from this period, like The Working Brain, present a picture of how cognition can work through what we would now call parallel, distributed processing, in which small brain regions perform specialized processing tasks, but none of the "higher cortical functions" maps directly, as it were phrenologically, onto a particular cortical area, but rather recruits these areas in shifting configurations. In particular, this would explain how lesions in single areas can lead to deficits in multiple functions, and conversely how there are many lesions which can cause a given functional deficit.
One could draw an analogy between this view of how the brain works and Marx's idea of how communism will overcome the division of labor. (This connection was never, so far as I know, even hinted at by Luria.) In a famous passage in The German Ideology, Marx and Engels write as follows:
[A]s soon as the distribution of labour comes into being, each man has a particular, exclusive sphere of activity, which is forced upon him and from which he cannot escape. He is a hunter, a fisherman, a herdsman, or a critical critic, and must remain so if he does not want to lose his means of livelihood; while in communist society, where nobody has one exclusive sphere of activity but each can become accomplished in any branch he wishes, society regulates the general production and thus makes it possible for me to do one thing today and another tomorrow, to hunt in the morning, fish in the afternoon, rear cattle in the evening, criticise after dinner, just as I have a mind, without ever becoming hunter, fisherman, herdsman or critic.Analogously, according to Luria, a region in the frontal cortex (say) might be involved in grammatical parsing in the morning, the planning of rapid motion in the afternoon, and mental arithmetic in the evening, without ever being a parser, a planner or a calculator exclusively. I am tempted to turn this conceit into a just-so story about why Hayek and Hebb, in their accounts of distributed neural information processing, put so much less emphasis on functional flexibility, but I am afraid that someone might take me seriously. (For the record: Marx and Engels's ideas on overcoming the division of labor were profoundly utopian, and that is not a compliment.)
For what it's worth, I think Luria was really on to something here, and the fundamental point against a purely "phrenological" view of the brain is valid. There are times when I wish that no one would write a press release about a neuroimaging study without reading The Working Brain first. (The rest of the time, I wish no one would write press releases about neuroimaging at all.) But I also think it's really a matter of how much and in what manner. Part of the subtext of my own work on information in networks is to develop tools to make these questions quantitative ones, about estimation, rather than qualitative ones, about interpretation.
Which is a good note on which to do some calculations...
Minds, Brains, and Neurons; The Progressive Forces; Afghanistan and Central Asia
Posted by crshalizi at March 30, 2007 16:06 |
| permanent link
Posted by crshalizi at March 30, 2007 15:38 |
| permanent link
Posted by crshalizi at March 30, 2007 15:38 |
| permanent link
Posted by crshalizi at March 30, 2007 15:38 |
| permanent link
Well, do you? If so, it's probably the casino magnetically stimulating your right dorsolateral prefrontal cortex:
How long, I wonder, before the tinfoil hat becomes the hallmark of the professional gambler?
Posted by crshalizi at March 30, 2007 15:38 |
| permanent link
Becaue this worked pretty well last time:
Hey, kid! Got anything lined up for the summer? No? Interested in winning eternal intellectual glory and entering the glamorous world of scientific research? Interested in $1500 a month for two summer months? Are you an undergrad at Carnegie Mellon University? If so, the statistics department has no less than eleven possible projects for you. (One of them is mine, building on this paper.) Apply now!
Posted by crshalizi at March 30, 2007 12:38 |
| permanent link
Posted by crshalizi at March 29, 2007 11:51 |
| permanent link
Via John Burke in e-mail, a fantastic video of the Helsinki Complaints Choir --- i.e., a choral work, reciting complaints collected around Helsinki.
A Pittsburgh complaints choir is being organized by Jen and Ray Strobel, and turns out to be rehearsing just down the street from where I live. Details here (under "January 23, 2007"). I am a little disappointed that we will no longer be able to grumble about having less amusing conceptual public art than the Finns.
Manual trackback: Nanopolitan
Posted by crshalizi at March 29, 2007 11:51 |
| permanent link
There is an old Soviet-era joke about a nail factory which was assigned a target, under the five year plan, of 1600 tons of nails, and spent the whole five years producing a single gargantuan nail weighing (of course) 1600 tons. The joke illustrates not only the follies of "actually existing socialism", but a broader problem with using quantitative performance targets, namely that people will tend to to meet the quantitative criteria, which can be only very poorly related to the real job they are supposed to be doing. This is not to say that objective performance criteria are always bad, because often the alternative is subjective evaluations by superiors, i.e., prejudice and caprice; but it does point to the need to carefully design those criteria, so that, as far as possible, they track what you actually want to have happen, and not just what's easy to measure or to calculate.
One place where easy calculation threatens to overwhelm substantive validity is in "bibliometrics", or the use of numerical methods to study patterns of scientific publication. For many years now, scientific journals have been advertising their "impact factor", as determined by ISI/Thompson Scientific, which is roughly the number of citations (as tracked by ISI/Thompson) to that journal, divided by the number of papers published in the journal. The idea is that journals with high impact factors are ones which publish articles people take note of, and go on to cite. Now, leaving to one side the big gap between "is cited a lot" and "is good science", there are huge, glaring holes with this as a way of measuring the quality or influence of a journal. An obvious one is that a citation from the World Journal of Cartesian Snooker and Even More Obscure Problems means much less than one from Nature. But another problem, perhaps even larger, is that different fields have different patterns of citation.
A stereotypical math paper, for example, will use a huge number of previously existing results, but contain very few citations, on the presumption that most of those results are assimilated background which its readers have already absorbed from any number of standard sources. If I write a paper on stochastic processes, I might well use the ergodic theorem for Markov chains, which says (roughly) that there is a way of assigning probabilities to states which is invariant under the chain's dynamics, and moreover the amount of time any sufficiently long trajectory spends in any one state is equal to that state's probability. This is a result with a very intricate history, going back to Markov himself in his struggles with his arch-enemy, but I'd look ridiculous if I cited any of this history, or even a textbook like Grimmett and Stirzaker. On the other hand, sociologists have a reputation for providing as many citations as possible for absolutely everything, and a pious habit of referring back to the 19th and early 20th century Masters. A leading sociology journal, then (say, American Journal of Sociology) might have an impact factor of around 5, while a leading mathematics journal (say, Annals of Probability) would have one significantly lower, even though both are near the top of their respective prestige hierarchies.
Now, you could say this is just another reason why we shouldn't try to rank journals. But there are times when doing things like this is going to be very helpful, e.g. when trying to decide which journals to spend a limited subscription budget on. So it would be nice if there was a way of doing something like this, which corrected for problems like the differences in citation customs across academic tribes.
One way to imagine doing this is as follows. Pick a completely random journal, and a random article from that journal. Now pick one of its references, again completely at random, and follow it up. Repeat this process by following a random reference in that paper, until you come to a dead end, namely a citation to something outside of your data set. Pick another random starting point and repeat, many times. Looking back over your random walks through the scientific literature, how much time did you spend in any given journal? It's not hard to convince yourself that you will spend more time in journals whose papers are highly cited by papers in other journals which are themselves highly cited. If you come to a paper with many references, you are that much less likely to follow any one of them, and so you will spend less time, all else being equal, on those papers than you will in the references of papers which are more sparing of citation. Saying "influential journals are ones which are often cited by influential journals" makes the definition sound hopelessly circular, but the random walk procedure makes it clear that it's not, or at least not hopelessly so.
It turns out that the random walk scheme is computationally very demanding — you need a lot of random walkers, taking a lot of very long walks, to get good results — but there is a short cut. The random process I've described is a well-behaved Markov chain. The ergodic theorem now tells us that a time average (how often does the walk hit a given journal?) can be replaced with a "space" average (what is the probability of being at a given journal?), where the probability weights are left unchanged by the action of the Markov chain. Finding these invariant distributions is an exercise in linear algebra; specifically it's going to be the leading eigenvector of the chain's transition matrix. (One of the beauties of the theory of Markov processes is how it lets us replace nasty nonlinear problems about individual trajectories with clean linear problems about probabilities.) And there are very nice, very fast algorithms for finding eigenvectors, even of very large matrices.
Thus the reasoning behind eigenfactor.org, the latest brainstorm from Carl Bergstrom's lab — most of the actual code and elbow-grease being provided by Jevin West and Ben Althouse. It covers all the journals that impact factor would, but also gives an estimate of the impact of citations to non-journals (which lets us see that some software is more influential than some journals). Plus you get to see all kinds of useful things about how much the journals cost (something Carl's been interested in for some time), and how that breaks down by paper or by citation. All in all, it's a very fun and potentially very useful tool for anyone interested in the academic publishing system, and/or applications of Markov chains.
Disclaimer/Incestuous Amplification: Rumors that Carl arranged for me to publicize everything his lab does in this weblog in exchange for beers from his private collection whenever I'm in Seattle are — sadly exaggerated.
Manual trackback: Geomblog; Muck and Mystery; Outsider; Structure+Strangeness; Flags and Lollipops
(Thanks to Own "Vlorbik" Thomas for typo correction.)
Posted by crshalizi at March 23, 2007 10:14 |
| permanent link
Posted by crshalizi at March 22, 2007 17:46 |
| permanent link
Academic life, especially in its sillier and more exasperating aspects.
Posted by crshalizi at March 22, 2007 14:19 |
| permanent link
Posted by crshalizi at March 20, 2007 21:09 |
| permanent link
...will be held July 9--13, 2007, at the Centre de Recherches Mathématiques, Université de Montréal, organized by David Campell, Giles Hooker and Jim Ramsay. They could hardly have come up with something I'd be more into if they'd been trying (which they weren't):
The term "dynamic system" typically implies a mathematical model expressed by a system of nonlinear differential or difference equations. Models of this nature have had a very long history in the physical sciences. More recently, these models have been employed for new areas such as clinical medicine, ecology, neurophysiology and the social sciences. There is, in addition, more and more attention given to assessing how well these models fit measured data in addition to displaying characteristics of the system being modeled at a qualitative level.Statisticians have played a relatively limited role in these developments, in part because methods for fitting data with models of this nature that could spin off approaches to testing hypotheses and supplying confidence intervals for estimated quantities have not been easy to develop. Consequently, we have proposed this workshop as a means of bringing those working with dynamic models together with statisticians so as to stimulate further development, collaboration and application of statistical methodology in this important area.
Official website here (or, in French, here). Financial support is available for graduate students.
This is also a good occasion to plug some of the work of the organizers, which I've been meaning to do since Hooker came here to give a talk about a year ago:
There has been a lot of work in the physical and nonlinear dynamics communities on reconstructing the state space of smooth dynamical systems (a.k.a. "geometry from a time series"), which more or less assumes that the time series you're interested in is the solution to a set of nonlinear differential equations. (Much of my own work has been based on these ideas, as extended to certain kinds of discrete stochastic processes.) What it concentrates on are the "qualitative" properties of the system, like the geometric type of the attractor, or the Lyapunov exponents. (More exactly, "qualitative" here means "left alone by a smooth change of coordinates", or in the jargon "invariant under a diffeomorphism". This is how the numerical values of the Lyapunov exponents, i.e., quantities, get to be "qualitative".) The strength of these methods --- not needing to know the actual variables comprising the physical state, or the precise form of the dynamics --- is also their weakness; they can tell us that we're dealing with a limit cycle, but not (say) how strongly the calcium and potassium concentrations are coupled.
To answer questions of the latter sort, we need information about the form of the equations of motion and their parameters. Perhaps oddly, the nonlinear dynamics community has done less work on these questions. (Less, but not exactly none.) But this is precisely what Ramsay et al. are doing, by ingeniously using existing spline-smoothing techniques to learn the parameters of the equations of motion in a statistically reliable manner. This opens the door to testing hypotheses about those parameters (are calcium and potassium concentrations coupled? are they as strongly coupled as other experiments would suggest?, etc.), estimating errors, and all the other conveniences of statistical inference. Those of us who care about modeling dynamics should all be very interested in what these two approaches can be made to say to each other.
Posted by crshalizi at March 20, 2007 21:09 |
| permanent link
The taxonomy of the yeti, the sasquatch, and related fauna has long been a vexed question. The most common position, exemplified by the magisterial work of Sanderson (still in print after forty years!) is that they are primates and probably either apes from some otherwise-extinct genus (e.g., Gigantopithecus), or hominids. The Church of the SubGenius, of course, lays down that SubGenii are, in fact, "Tibetan yetis from Atlantis" (among other things). A more extravagant suggestion was Lovecraft's, that they were mobile, intelligent extraterrestrial fungi, based in this solar system on Yuggoth (traditionally identified by commentators with Pluto, though whether that will survive the recent demotion of that body is unclear). I am happy to report, however, that the taxonomic question has recently been solved, through the power of Science.
To quote from the Milinkovitch et al. paper:
In 1992, Peter Matthiessen and photographer Thomas Laird were the first Westerners in over three decades to visit a remote region in the northernmost Himalaya. Located close to the boarder of Tibet, Sao Kohla is a mysterious valley outside of the main city of Lo Monthang. Here Matthiessen, Laird, and their Nepalese colleagues came upon some unusual foot prints in the snow, and were informed by locals that they were the prints of the Mehti (the local name for Yeti). Near a river at the bottom of the gorge, samples of twisted hair were recovered which were clearly identified as Mehti hair by their local guides (Matthiessen, 1995, p. 75--80). We were asked to analyze these samples, but first had to agree that any identification of a "new species" would have to be reported to the government of Nepal before publication.
They sequenced mitochondrial ribosomal RNA from the samples, and constructed a phylogenetic tree, which I reproduce below:
Similarly for Coltman and Davis:
In July 2005, nine residents of Teslin, Yukon, witnessed through a kitchen window a large bipedal animal moving through the brush. The next morning, they collected a tuft of coarse, dark hair and also observed a footprint measuring 43 cm in length and 11.5 cm in width. The tuft of hair was sent to Philip Merchant, a wildlife technician of the Government of Yukon Department of Environment...and so eventually to the authors, who sequenced the DNA. This produced the following tree:
A simple application of the comparative method leads us to conclude that both in western North America and in the Himalayas curious selective pressures have resulted in the convergent evolution of two different groups of ungulates with primates.
In all seriousness, it's not completely implausible that large mammals, even primates, remain undiscovered. As Coltman and Davis note, a new of bovid was described in Vietnam in 1992, and a new species of monkey in Tanzania in 2003, so it's by no means impossible that there is an undescribed primate at large in the Himalayas, or that something rare is shambling around in the Yukon. If you want fodder for speculation, note that Gigantopithecus is known to have survived to about 100,000 years ago, and the ground sloths even more recently than that in the Americas. (Of course, given the degree of armed conflict in and around the Himalayas in recent years, I for one find it only too easy to further imagine the last yetis getting caught in the cross-fire between India and Pakistan, or the Nepalese government and the Maoists.) But, really, every culture I've ever heard of has legends about the roughly human-sized and roughly human-shaped, but not human, creatures who live nearby, and for pretty obvious reasons. I honestly don't see any why cryptozoologists should take these stories more seriously when they come from Nepal or the Yukon than when the come from the British Isles.
(Thanks to Danny Yee for alerting me to these papers.)
Manual trackback: Pathologically Polymathic; Chrononautic Log; Untyping; Greg Laden; Gene Expression; MetaFilter; Southeast Sasquatch Association.
Posted by crshalizi at March 20, 2007 20:16 |
| permanent link
Posted by crshalizi at March 10, 2007 18:29 |
| permanent link
Posted by crshalizi at March 09, 2007 16:53 |
| permanent link
Via Nanopolitan, Yoram Bauman's hilarious and accurate translation of Greg Mankiw's "ten principles of economics", from the Annals of Improbable Research. (Bauman's free downloadable principles textbook, Quantum Microeconomics, looks interesting and, despite the title, sound; and reminds me that I still need to finish my post on econophysics.)
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Posted by crshalizi at March 09, 2007 16:50 |
| permanent link
Much to my loss (and, less importantly, embarrassment), I had never read this before this week. It really is as brilliant as everyone says, one of Lem's best, and bleakest, meditations on intelligence and alienness, cosmic strangeness and human pain. Most science fiction, like most fiction of any kind, is crap. Of the rest, most is mere brain-candy (which I devour eagerly, see side-bar at left). Of the rest, most is the literature of the great transformation, of humanity's passage out of pre-industrial darkness (perhaps into a different kind of darkness). This is science fiction as a literature that goes beyond the confines of our species.
I will not attempt a proper review, but I do want to draw out just one thread — I'm sure it's an old story to those who actually study Lem. The novel seems to owe something to two classic American stories of alien contact in the Antarctic, Lovecraft's At the Mountains of Madness and John W. Campbell's "Who Goes There?", though I have no idea if that's even historically possible, and Solaris is unquestionably at a far higher intellectual level. (There are a few places where the passage from Polish to English via French has reduced technical terms to gobbledygook, though I think I can guess what Lem meant.) In fact, I can't help but wonder if Solaris wasn't, in part, Lem's response to the challenge Campbell, as editor, set to his authors: "Write me a creature that thinks as well as a man, or better than a man, but not like a man". All those writers failed. (I think Lovecraft wanted to do this, but his best efforts ran a-ground in sentiments like this: "Radiates, vegetables, monstrosities, star spawn — whatever they had been, they were men!"). Lem actually succeeded here in making his readers imagine something which is so orthogonal to any sort of terrestrial mentality that even terms like "mind" or "intelligence" seem dubious, but inescapable. That he achieves this effect through, in part, an even more extreme version of the literal anthropomorphism indulged in by Campbell, that is artistry.
There is artistry, too, in the way Lem's protagonist realizes he has had a profound encounter with the utterly alien, but what matters to him is the all-too-human hope its side-effects offer of a tormented emotional redemption. "I knew nothing, and I persisted in the faith that the time of cruel miracles was not past."
Merry Christmas.
Posted by crshalizi at March 05, 2007 23:55 |
| permanent link
If you are in love, then this is obviously the most appropriate and touching image for the holiday. If you are out of love, then this is, again, the most appropriate image for the holiday:
(Via Sean Carroll at Cosmic Variance, who evidently belongs to the former set.)
Posted by crshalizi at March 05, 2007 15:34 |
| permanent link
On the one hand, this rings true.
On the other hand, I'm still going to Scott Aaronson's talk this afternoon.
Posted by crshalizi at March 05, 2007 15:34 |
| permanent link
Hosted, but not endorsed, by the Center for
the Study of Complex Systems