so random

September 28, 2009 at 1:10 pm

| Gabriel |

Nate Silver at 538 has accused Strategic Vision of fudging their numbers and his argument is simply that few of their estimates end in “0” or “5” and a lot of them end in “7.” The reason this is meaningful is that there’s a big difference between random and the perception of random. A true random number generator will give you nearly equal frequency of trailing digits “0” and “7,” but to a human being a number ending in “7” seems more random than one ending in “0.” Likewise clusters occur in randomness but human beings see clustering as suspicious. A scatterplot of two random variables drawn from a uniform has a lot of dense and sparse patches but people expect it to look like a slightly off-kilter lattice. That is, we intuitively can’t understand that there is a difference between a uniform distribution and a random variable drawn from a uniform distribution.

This reminded me of two passages from literature. One is in Silence of the Lambs when Hannibal Lector tells Clarice that the locations of Buffalo Bill’s crime scenes is “desperately random, like the elaborations of a bad liar.” The other is from Stephenson’s Cryptonomicon, where a mathematician explains how he broke a theoretically perfect encryption scheme:

That is true in theory, … In practice, this is only true if the letters that make up the one-time pad are chosen perfectly randomly … An English speaker is accustomed to a certain frequency distribution of letters. He expects to see a great many e’s t’s, and a’s, and not so many z’s and q’s and x’s. So if such a person were using some supposedly random algorithm to generate the letters, he would be subconsciously irritated every time a z or an x came up, and, conversely, soothed by the appearance of e or t. Over time, this might skew the frequency distribution.

Going a little bit further afield, in a recent bloggingheads, Knobe and Morewidge discuss the latter’s psych lab research on various issues, including how people tend to ascribe misfortune to malicious agency but fortune to chance. They then note that this is the opposite of how we tend to talk about God, seeing fortune as divine agency and misfortune as random. This is true for Americans, but this has less to do with human nature than with the unusual nature of the Abrahamic religions.*

Ironically, the lab research is pretty consistent with the modal human religious experience — animism organized around a “do ut des” relationship with innumerable spirits that control every aspect of the natural world. Most noteworthy is that much of this worship appears aimed not at some special positive favor but at getting the gods to leave you alone. So the Romans had sacrifices and festivals to appease gods like Robigus, the god of mold, and Cato the Elder’s De Agricultura explains things like how when you clear a grove of trees you need to sacrifice a pig to the fairies who lived in the trees so they don’t haunt the farm. These religious practices seem pretty clearly derived from a human tendency to treat misfortune as the result of agency and to generalize this to supernatural agency, absent cultural traditions to the contrary.

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*I generally get pretty frustrated with people who talk about religion and human nature proceeding from the assumption that ethical monotheism and atheism are the basic alternatives. Appreciating that historically and pre-historically most human beings have been animists makes the spandrel theory of hyper-sensitive agency-detection much more plausible than the group-selectionist theory of solidarity and intra-group altruism.

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