About Rationally Speaking

Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.

Saturday, January 19, 2013

Ian’s Picks

by Ian Pollock

* Richard Chappel (channeling Derek Parfit) clarifies issues of personal identity, “one case where common-sense is utterly senseless.”

* RS readers may be interested to know that many of the topics we love to discuss, such as probability updating and cognitive biases, are also discussed a lot in the poker community. For example, here is Barbara Connors on the Texas sharpshooter fallacy and the sunk cost fallacy. I can confirm that poker is excellent practice for really “getting” concepts like calibration and expected utility. Too bad the culture is so irritatingly macho.

* Brian Earp of Practical Ethics argues that the recent push for adult male circumcision to prevent HIV transmission is based on bad science, compounded by misleading statistical trickery.

* The Ford Pinto case is known for Ford’s infamous use of cost/benefit calculations that “put a dollar value on human life.” It is even referenced in Michael Sandel’s lectures on ethics, as a reductio of heartless utilitarian calculus. But like many pop-culture legends, the details are more complicated. Key points, which can be gleaned from this interesting article: (1) the Pinto was a severely flawed vehicle; (2) the famous cost-benefit calculation had nothing directly to do with the Pinto; (3) the dollar figure on human life ($200,000) was specified as a target by auto regulators, not Ford; (4) it is not clear how regulators or corporations are supposed to make any coherent safety decisions without using cost/benefit analysis.

* Finally, since time immemorial, January has provided an opportunity to reflect on our predictions for the future — will the crops be good, will the earth be wiped out by a meteor, et cetera. Here are some interesting variations on that theme:

The Calibration Game (great for queues)
PredictionBook (group calibration practice)

RS readers: now’s your chance to record your longshot predictions (along with your credences, of course), so you can legitimately crow about them later!


  1. If you like Barbara Connors and “sunk cost”, check out Dan Ellsberg’s book, “Risk, Ambiguity, and Decision”, or read (for free) the article it was based upon: “Risk, Ambiguity, and the Savage Axioms”.

    Available at: http://www.nssl.noaa.gov/users/brooks/public_html/feda/papers/ellsberg1961savage.pdf

    1. I think I will read that book. The article is very interesting, although I confess my intuitions are totally indifferent between bets in these cases of ambiguity.

      I think what's intuitively throwing us off is that an "ambiguous" bet carries with it a high value for further information. So if you offered me a bet at say 1.2:1 on

      (a) a coin flip coming up heads; or
      (b) the democrats winning in 2016 (to which I assign about 1:1 odds)

      my response would not be a *preference* for the coin flip, just a request for an hour on google to investigate recent polling etc.

      If you refuse to give me an hour on google, then I have no preference between the two bets. (Well, except that I can collect earlier on the coin flip. Nevermind that factor.)

  2. Small problem with the circumcision article. Although it is well and good to question the methodology of this kind of study, I have an issue with the following statement by Earp:

    "That’s right: 60% is the relative reduction in infection rates, comparing two vanishingly small percentages: a clever bit of arithmetic that generates a big-seeming number, yet one which wildly misrepresents the results of the study. The absolute decrease in HIV infection between the treatment and control groups in these experiments was a mere 1.31%, which can hardly be considered clinically significant, especially given the numerous confounds that the studies failed to rule out."

    Ahem! If I say the rate of something is decreased by 60% due to some measure, it means this: The rate after the measure is applied is 40% lower than the rate without the measure. That is all.

    For example, suppose I read a study that shows that using seat belts decreases the rate of fatalities from traffic accidents by 60%. I am smart enough to know that the rate wasn't (X + 60)% before the measure, and is X% after the measure. If there are 1000 deaths for every million accidents without seat belts, then this means there would be 400 deaths for every million accidents with seat belts. This isn't some "clever bit of arithmetic", it's just common sense. I just wish Earp could see that. I'm sure he'd be happy to point out that wearing seat belts only decreases the risk of death from traffic accidents by .06% (assuming my hypothetical numbers).

    1. Correcting myself: "The rate after the measure is applied is 40% lower than the rate without the measure" should read: "The rate after the measure is applied is 40% of the rate without the measure."


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