February 05, 2019

"Causal inference in social networks: A new hope?" (Friday at the Ann Arbor Statistics Seminar)

Attention conservation notice: Self-promoting notice of a very academic talk, at a university far from you, on a very recondite topic, solving a problem that doesn't concern you under a set of assumptions you don't understand, and wouldn't believe if I explained to you.

I seem to be giving talks again:

"Causal inference in social networks: A new hope?"
Abstract: Latent homophily generally makes it impossible to identify contagion or influence effects from observations on social networks. Sometimes, however, homophily also makes it possible to accurately infer nodes' latent attributes from their position in the larger network. I will lay out some assumptions on the network-growth process under which such inferences are good enough that they enable consistent and asymptotically unbiased estimates of the strength of social influence. Time permitting, I will also discuss the prospects for tracing out the "identification possibility frontier" for social contagion.
Joint work with Edward McFowland III
Time and place: 11:30 am -- 12:30 pm on 8 February 2019, in 411 West Hall, Statistics Department, University of Michigan

--- The underlying paper grows out of an idea that was in my paper with Andrew Thomas on social contagion: latent homophily is the problem with causal inference in social networks, but latent homophily also leads to large-scale structure in networks, and allows us to infer latent attributes from the graph; we call this "community discovery". Some years later, my student Hannah Worrall, in her senior thesis, did an extensive series of simulations showing that controlling for estimated community membership lets us infer the strength of social inference, in regimes where community-discovery is consistent. Some years after that, Ed asked me what I was wanting to work on, but wasn't, so I explained about what seemed to me the difficulties in doing some proper theory about this. As I did so, the difficulties dissolved under Ed's questioning, and the paper followed very naturally. We're now revising in reply to referees (Ed, if you're reading this --- I really am working on it!), which is as pleasant as always. But I am very pleased to have finally made a positive contribution to a problem which has occupied me for many years.

Constant Conjunction Necessary Connexion; Enigmas of Chance; Networks; Self-Centered

Posted at February 05, 2019 21:04 | permanent link

February 03, 2019

On Godzilla and the Nature and Conditions of Cultural Success; or, Shedding the Skin

Attention conservation notice: 1100+ words of Deep Thoughts on a creature-feature monster and cultural selection, from someone with no qualifications to write on either subject. Expresses long-held semi-crank notions; composed while simultaneously reading Morin on diffusion chains and drinking sake; revived over a year after it was drafted because Henry was posting about similar themes, finally posted because I am procrasting finishing a grant proposal celebrating submitting a grant proposal on time.

Godzilla is an outstanding example of large-scale cultural success, and of how successful cultural items become detached from their original meanings.

Godzilla's origins are very much in a particular time and place, namely Japan, recently (if not quite immediately) post-WWII and the national trauma of the atomic bombings and their lingering effects. This is a very particular setting, on the world-historical scale. It is now seven decades in the past, and so increasingly gone from living memory, even for the very long-lived population of Japan.

Against this, Godzilla has been tremendously successful culturally all over the world, over basically the whole time since it appeared. I don't mean that it's made money (thought it has) --- I mean that it has been popular, that people have liked consuming stories (and images and toys and other representations) about it, that they have liked creating such representations, and that they have liked thinking about and with Godzilla.. (In contemporary America, for instance, Godzilla is so successful that the suffix "-zilla" is a morpheme, denoting something like "a destructive, mindlessly-enraged form of an entity".) Necessarily, the vast majority of this success and popularity has been distant in time, space, social structure and cultural context from 1950s Japan. How can these two observations --- the specificity of origins and the generality of success --- be reconciled?

To a disturbing extent, of course, any form of cultural success can be self-reinforcing (cf. Salganik et al.), but there is generally something to the representations which succeed (cf., again, Salganik et al.). But, again, Godzilla is endemic in many contexts remote in space, time and other cultural features from immediately-post-war Japan. So it would seem that whatever makes it successful in those contexts, including here and now as I write this, must be different from what made it successful at its point of origin.

It could be that Godzilla is successful in 1950s Japan and in 2010s USA because it happened to fit two very different but very specific cultural niches --- the trauma of defeat culminating in nuclear war, on the one hand; and (to make something up) a compulsive desire for re-enactments of 9/11 on the other hand. But explaining wide-spread success by a series of particular fits falters as we consider all the many other social contexts in which Godzilla has been popular. Maybe it happened, by chance, to appeal narrowly to one new context, but two? three? ten?

An alternative is that Godzilla has managed to spread because it appeals to tastes which are not very context-specific, but on the contrary very widely distributed, if not necessarily constant and universal. In the case of Godzilla, we have a monster who breaks big things and breathes fire: an object of thought, in other words, enduringly relevant to crude interests in predators, in destruction, and in fire. Since those interests are very common across all social contexts, something which appeals to them has a very good source of "pull".

This is not to say that Godzilla wasn't, originally, all about being the only country ever atom-bombed into submission. But it is to say that we can draw a useful distinction between the meanings successful cultural products had originally and those attached to them as they diffuse. It is analogous to the distinction the old philosophy of science used to draw between an idea's "context of discovery" and its "context of justification", though that had a normative force I am not aiming at. (For the record, I think that many of the criticisms of the discovery-justification distinction are weak, mis-conceived or just flat wrong, and that it's actually a pretty useful distinction. But that's another story for another time.)

For Godzilla, like many other successful cultural products, the "context of invention" was a very historically-specific confluence of issues, concerns and predecessors. But the "context of diffusion" was that it could appeal to vastly more generic tastes, and make use of vastly more generic opportunities. These are still somewhat historically-specific (e.g., no motion-picture technology, no Godzilla), but much less so. I am even tempted to formulate a generalization: the more diffused a cultural product is, in space or time or social position, the less its appeal owes to historically-specific contexts, and the more it owes to forces which are nearly a-historical and constant.

What holds me back from declaring cultural diffusion to be a low-pass filter is that it is, in fact, logically possible for a cultural product to succeed in many contexts because it seems to be narrowly tailored to them all. What's needed, as a kind of meta-ingredient, is for the cultural product to be suggestively ambiguous. It is ambiguity which allows very different people to find in the same artifact the divergent but specific meanings they seek; but it also has to somehow suggest to many people that there is a specific, compelling meaning to be found in it. When we consider cultural items which have endured for a very long time, like some sacred texts or other works of literature, then I suspect we are seeing representations which have been strongly selected for suggestive ambiguity.

It is a cliche of literary criticism that each generation gives its own interpretation of these great works. It is somewhat less of a cliche, though equally true, that every generation finds a reason to interpret them. Pace Derrida and his kin, I don't think that every text or artifact is equally amenable to this sort of re-interpretation and re-working. (Though that notion may have seemed more plausible to literary scholars who were most familiar with a canon of books inadvertently selected, in part, for just such ambiguity.) There are levels of ambiguity, and some things are just too straightforward to succeed this way1. It is also plainly not enough just to be ambiguous, since ambiguous representations are very common, and usually dismal failures at propagating themselves. The text or artifact must also possess features which suggest that there is an important meaning to be found in it2. What those features are, in terms of rhetorical or other sorts of design, is a nice question, though perhaps not beyond all conjecture. (I strongly suspect Gene Wolfe of deliberately aiming for such effects.) Something keeps the great works alive over time and space, saving them from being as dead as Gilgamesh, of merely historical interest. Because they are interpreted so variously, they can't be surviving because any one of their interpretations is the right one, conveying a compelling message that assures human interest. Rather, works outlast ages precisely because they simultaneously promise and lack such messages. This quality of suggestive ambiguity could, of course, also contribute to academic and intellectual success --- making it seem like you have something important to say, while leaving what that thing is open to debate, is one route to keeping people talking about you for a long time.

… or so I think in my more extreme moments. In another mood, I might try to poke holes in my own arguments. As for Godzilla, I suspect it's too early to tell whether it possesses this quality of suggestive ambiguity, but my hunch is that this dragon is not a shape-shifter.


  1. I seem to recall that Umberto Eco once, to make this point, had a parable about employing a screw-driver to clean out your ears. But if my memory has not invented this, I cannot now find the passage.^

  2. Though, again, we should be aware of the self-reinforcing nature of cultural success, the way that something might seem important to re-interpret or re-work in part because it is already widely known.^

The Collective Use and Evolution of Concepts; Scientifiction and Fantastica

Posted at February 03, 2019 15:08 | permanent link

Data Over Space and Time

Collecting posts related to this course (36-3467/36-667).

Posted at February 03, 2019 14:15 | permanent link

Three-Toed Sloth