Wednesday, September 28, 2011

Skeptics and Bayesian epistemology

A few prominent skeptics have been arguing that science and medicine should rely upon Bayesian epistemology.  Massimo Pigliucci, in his book Nonsense on Stilts, on the Rationally Speaking podcast, and in his column in the Skeptical Inquirer, has suggested that scientists should best proceed with a Bayesian approach to updating their beliefs.  Steven Novella and Kimball Atwood at the Science-Based Medicine blog (and at the Science-Based Medicine workshops at The Amazing Meeting) have similarly argued that what distinguishes Science-Based Medicine from Evidence-Based Medicine is the use of a Bayesian approach in accounting for the prior plausibility of theories is superior to simply relying upon the outcomes of randomized controlled trials to determine what's a reasonable medical treatment.  And, in the atheist community, Richard Carrier has argued for a Bayesian approach to history, and in particular for assessing claims of Christianity (though in the linked-to case, this turned out to be problematic and error-ridden).

It's worth observing that Bayesian epistemology has some serious unresolved problems, including among them the problem of prior probabilities and the problem of considering new evidence to have a probability of 1 [in simple conditionalization].  The former problem is that the prior assessment of the probability of a hypothesis plays a huge factor in the outcome of whether a hypothesis is accepted, and whether that prior probability is based on subjective probability, "gut feel," old evidence, or arbitrarily selected to be 0.5 can produce different outcomes and doesn't necessarily lead to concurrence even over a large amount of agreement on evidence. So, for example, Stephen Unwin has argued using Bayes' theorem for the existence of God (starting with a prior probability of 0.5), and there was a lengthy debate between William Jefferys and York Dobyns in the Journal of Scientific Exploration about what the Bayesian approach yields regarding the reality of psi which didn't yield agreement. The latter problem, of new evidence, is that a Bayesian approach considers new evidence to have a probability of 1, but evidence can itself be uncertain.

And there are other problems as well--a Bayesian approach to epistemology seems to give special privilege to classical logic, not properly account for old evidence [(or its reduction in probability due to new evidence)] or the introduction of new theories, and not be a proper standard for judgment of rational belief change of human beings for the same reason on-the-spot act utilitarian calculations aren't a proper standard for human moral decision making--it's not a method that is practically psychologically realizable.

The Bayesian approach has certainly been historically useful, as Desiree Schell's interview with Sharon Bertsch McGrane, author of The Theory That Would Not Die: How Bayes’ Rule Cracked the Enigma Code, Hunted Down Russian Submarines, and Emerged Triumphant from Two Centuries of Controversy, demonstrates.  But before concluding that Bayesianism is the objective rational way for individuals or groups to determine what's true, it's worth taking a look at the problems philosophers have pointed out for making it the central thesis of epistemology.  (Also see John L. Pollock and Joseph Cruz, Contemporary Theories of Knowledge, 2nd edition, Rowman & Littlefield, 1999, which includes a critique of Bayesian epistemology.)

UPDATE (August 6, 2013): Just came across this paper by Brandon Fitelson (PDF) defending Bayesian epistemology against some of Pollock's critiques (in Pollock's Nomic Probability book, which I've read, and in his later Thinking About Acting, which I've not read).  A critique of how Bayesianism (and not really Bayesian epistemology in the sense defended by Fitelson) is being used by skeptics is here.

Monday, September 12, 2011

Rarely-used cliche on the Token Skeptic podcast

My favorite part of the Token Skeptic podcast #76's interview with Sara Mayhew and Jack Scanlan is 28:30-28:42, where Scanlan says "everyone hates pop songs."  That's a self-annihilating sentence along the lines of "No one goes there anymore; it's too crowded."

That reminds me of Saul Gorn's compendium, "Self-Annihilating Sentences: Saul Gorn's Compendium of Rarely Used Cliches," which I have in the original hardcopy but is now available online for everyone's enjoyment.

Saturday, September 03, 2011

The origins of Screaming Trees?

Here's a famous photograph of pulp fiction author and Scientology creator L. Ron Hubbard holding a tomato plant connected to an E-Meter.  Hubbard claimed in 1968 that tomatoes would "scream when sliced," as detected by the E-Meter. [UPDATE: The photo appeared in "30 Dumb Inventions" on Life magazine's website, attributed to the Evening Standard of January 1, 1968, but the claims and the photo appear to be from 1959, see below.]

Hubbard was likely inspired by Cleve Backster, who had made similar claims based on connecting plants to a polygraph starting in 1966.  Backster published his claims in the Journal of Parapsychology in 1968, and his work was subsequently popularized in the 1973 book, The Secret Life of Plants.

I wonder, however, whether the inspiration for both of these crackpots came from a piece of fiction in the September 17, 1949 issue of The New Yorker--Roald Dahl's "The Sound Machine," which is reprinted in numerous short story collections, including his volume Someone Like You (1973). In this tale, a man named Klausner, obsessed with sounds beyond the ability of human beings to hear, builds a machine to convert higher pitches into human-audible sounds.  He discovers, to his horror, that plants and trees shriek with pain when cut.

Does anyone know of any documented references from Hubbard or Backster to Dahl?  Or is there another common ancestor I've missed?

My title includes a reference to the Seattle-area grunge band, Screaming Trees, whose Wikipedia entry doesn't comment on the origin of their name--but Dahl's story seems a likely inspiration there, too.

UPDATE (6 February 2013): It looks like the Hubbard photo pre-dates Backster, and was likely taken in 1959 or 1960!  It prompted a feature titled "PLANTS DO WORRY AND FEEL PAIN." in the December 18, 1959 Garden News.

UPDATE (10 February 2013): David Hambling's "The Secret Life of Plants" in the December 2012 issue of Fortean Times (p. 18) points out that Charles Darwin's 1880 The Power of Movement in Plants suggested that plants have something like a nervous system, and that Jagadish Chandra Bose published a 1907 paper on the electrophysiology of plants.  He puts Backster before Hubbard, making the same mistake of dating Hubbard's claims by the Life magazine photo caption.

Backster, by the way, was inspired by Bose's work.  He says that he started his work with plants on February 2, 1966, as reported in the introduction of his "Evidence of a Primary Perception in Plant Life," International Journal of Parapsychology, Vol. X, No. 4, Winter 1968, pp. 329-348.

UPDATE (21 October 2021): On a 1966 episode of the Joe Pyne Show, in discussion with Lewis Marvin, Pyne asserted that it has been scientifically proven that tomatoes scream when cut, likely referencing Backster.

UPDATE (5 December 2022): Not sure how I missed including the Jack Handy "Deep Thoughts" that goes: "If trees could scream, would we be so cavalier about cutting them down? We might, if they screamed all the time, for no good reason."

Thursday, September 01, 2011

Scott Atran on violent extremism and sacred values

Chris Mooney has a very interesting interview with anthropologist Scott Atran on the Point of Inquiry podcast, in which Atran argues that terrorism is not the product of top-down, radical religious extremist organizations recruiting the poor and ignorant, but of groups of educated (and often educated in secular institutions) individuals who become disaffected, isolated, and radicalized.  Much U.S. counterterrorism and "homeland security" activity assumes the former and thus is attacking the wrong problem.

He also argues that reason and rationalism are the wrong tools for attacking religion, defends a view of religion as a natural by-product of the sorts of minds we've evolved to have (very similar to Pascal Boyer's account, which I think is largely correct), and throws in a few digs at the new atheists for making claims about religion that are contrary to empirical evidence.

Some of the commenters at the Point of Inquiry/Center for Inquiry forums site seem to be under the misapprehension that Atran is a post-modernist.  I don't see it--he's not making the argument that reason doesn't work to find out things about the world, he's making the argument that the tools of science and reason are human constructions that work well at finding things out about the world, but not so much for persuading people of things, or as the basis for long-term institutions for the sort of creatures we are.  Atran shows up in the comments to elaborate on his positions and respond to criticism.

My compliments to Chris Mooney for having consistently high-quality, interesting guests who are not the same voices we always hear at skeptical conferences.