Wednesday, September 30, 2009

Carnival of the Africans #11

The 11th edition of the Carnival of the Africans is out over at The Skeptic Detective. My picks: Simon of Amaneunsis with some fact checking on pregnancy and sushi, George Claassen at Prometheus Unbound on religion in South African state schools, and Richard at The Botswana Skeptic on fortune tellers and the law...

We need a host for next month, so email me if you're interested...

Wednesday, September 23, 2009

Fun with fallacies: Poisoning the well

An unfortunate byproduct of philosophical training, other than the obvious of annoying everyone at the dinner table, is that I cry inwardly every time I see terms such as “fallacy” or “invalid” misused. On the theory that I shouldn’t complain about it if I’m not doing something about it, I figured I’d start an irregular series on critical thinking and logical fallacies. So, welcome to the inaugural edition of Fun with Fallacies…

First, some background. There are two different dimensions along which to evaluate arguments: one, the truth of premises and, two, the validity of argument structure. Premises (the content of arguments – e.g. “Scotland is in the Northern Hemisphere”, “All monkeys are purple”) are either true or false. Arguments (the logical structure linking premises – e.g. “If A then B, A therefore B”, “A and B, therefore C”) are either valid or invalid. And these two dimensions, importantly, are separate. In logic, saying a premise is invalid makes no sense: it is much like saying someone has scored a touchdown in soccer. Similarly, arguments cannot be true or false; they are only ever valid or invalid. As the perceptive reader no doubt noticed, my first example of a premise was true and the second was false and my first example of an argument was valid (if you like your Latin, this particular structure is known as modes ponens) and the second was invalid. Note that you can have an invalid argument with true premises and a true conclusion (“Elephants are mammals, Elvis Presley is dead, therefore homeopathy is bollocks”), that you can have a valid argument with false premises and a false conclusion (“All women are pregnant, Angela is a woman, therefore Angela is pregnant” "All women are pregnant, Michael is a woman, therefore Michael is pregnant") and so on. These dimensions are entirely independent of each other. When an argument is (1) valid AND (2) has all true premises, we say it is sound (and therefore one you should accept); otherwise, it is unsound.

But what exactly is validity? It’s quite simple really. A valid argument is one where the truth of the premises guarantees the truth of the conclusion. In other words, if the premises are true, it follows, by the laws of logic, that the conclusion must be true. (But not vice versa). If this is the case, we say the conclusion ‘follows’ from the premises or that the truth of the premises 'transmits' truth to the conclusion. So if “A” and “if A then B” are both true, then you are forced to conclude that “B” is true (this is modes ponens again). Or, in words, if Paris is the capitol of France (“A”), and Paris being the capitol of France entails that the French seat of government is in Paris (“if A then B”), then it follows that the French seat of government is in Paris (“B”).

Okay, so what’s a fallacy? It’s just an argument that is not valid – that is, it’s an argument where the conclusion does not follow from the premises. Notice, however, that the fact that some argument is a fallacy does not mean the premises are false, nor does it mean the conclusion is false. Indeed, saying an argument is fallacious (i.e. invalid) entails nothing whatsoever about the truth of the premises or the conclusion. (You can, after all, defend a true conclusion with an invalid argument). Conversely, just because an argument is valid does not mean the conclusion is true, nor does it mean the premises are true: it’s just that if the premises were true you would have to accept the conclusion. (So if it really were the case that all monkeys are purple and that I am a monkey, I would be forced to accept that I’m purple). The upshot is that a concern with validity and detecting fallacies is only one aspect of evaluating positions but, of course, it’s an important part.

That’s about enough background, I think, so on the our first actual example… Regular readers will recall that I recently took on a local (i.e. South African) homeopath, one Johan Prinsloo. In a section of his website that he’s now edited but which is still available on Google Cache as I first saw it, Prinsloo made the following argument (emphasis in original):
The one thing that always catches my attention is the fact that generally the skeptics of Homeopathy also tend to be anti-religion or at least skeptical of religion.
What’s going on here? Well, it’s a beautiful example of poisoning the well, which is a sub-type of the ad hominem fallacy (‘arguing to the man’). Ad hominem is pretty widely misunderstood; some people seem to think that any insult or negative assertion about an opponent makes an argument fallacious. This is not correct. In fact, ad hominem has the form: “Sarah believes that P, Sarah has negative quality X, therefore P is false”. Clearly, this argument is invalid: there is no premise linking having negative quality X and the truth or falsity of P. The important bit, though, is that a conclusion is being drawn about a claim from the purported negative quality, if this is not done no fallacy is being committed. I might say, for example, that: “Homeopathy is bollocks”, “homeopaths tend to be dumb”, “the law of infinitesimals is false” and so on. As long as I’m not drawing an inference from “homeopaths tend to be dumb”, all I’ve done is thrown around an insult (which may or may not be true), I have not committed a fallacy. (Remember, truth and falsity is independent of validity and invalidity!). It’s possible, in fact, to make the argument about Sarah valid (so it’s no longer a fallacy), despite the fact that it’s still about a negative quality. All I have to do is insert the missing premise: “Sarah believes that P, Sarah has negative quality X, everything people with negative quality X believe is false, therefore P is false”. Note that the conclusion now does follow from the premises and it’s thus no longer a fallacy, but at the cost of making the ridiculous missing (or ‘suppressed’) premise explicit.

In Prinsloo’s case it’s clear that he’s attempting to preempt criticism of homeopathy by (in his mind) tarnishing the reputation of the skeptics: he is, in other words, poisoning the well. He is implying that critics of homeopathy have a negative quality (being religious skeptics), and therefore their views on homeopathy can be dismissed. This argument is obviously fallacious as it stands: there is no premise linking being a religious skeptic to having false beliefs about homeopathy, and thus the conclusion does not follow from the stated premises. To make the argument valid, Prinsloo would have to say something like "everything a religious skeptic believes is false" or "everything religious skeptics say about homeopath is false" and once you see that, it becomes obvious why the premise was kept implicit: it's ridiculous on the face of it. As far as I am aware, there is not even correlational evidence between religious skepticism and having false beliefs (indeed the opposite might be true), let alone evidence that religious skeptics are invariably wrong.

Carnival of the Africans -- call for submissions

Angela Butterworth, The Skeptic Detective, will host the next edition of the Carnival of the Africans on the 28th. Please check out the guidelines, and then submit your posts to

Also, if you'd like to host an edition, email me at

Friday, September 18, 2009

Lazy Linking

"The Dark Matter of the Human Brain"
  • Carl Zimmer on how the neuron doctrine -- basically, that neurons do the computational heavy lifting in the brain -- might be wrong, or at least radically incomplete. Glial cells, it turns out, may be far more important than previously thought.
  • "If astrocytes [a type of glial cell] really do process information, that would be a major addition to the brain’s computing power. After all, there are many more astrocytes in the brain than there are neurons. Perhaps, some scientists have speculated, astrocytes carry out their own computing. Instead of the digital code of voltage spikes that neurons use, astrocytes may act more like an analog network, encoding information in slowly rising and falling waves of calcium. In his new book, The Root of Thought, neuroscientist Andrew Koob suggests that conversations among astrocytes may be responsible for 'our creative and imaginative existence as human beings.'"
  • Olivia Judson over at the NY Times on the horrendous way in which Simon Singh has been treated. Good news: the US senate is putting pressure on the English parliament to change their libel laws. Hopefully freedom of speech will prevail. 
"The Greatest Show on Earth: The Evidence for Evolution"
  • PZ's review of Dawkins' latest book.
  • "The enemy of ignorance is education, and the creationists know that; it's why there is so much effort by the religious conservatives to destroy public education. These are books that provide an end-run around the current deficiencies in science education in this one area, and what they ought to do is help people question the wanna-be theocrats. If they lie about evolution, if they are so transparently wrong about this one subject, maybe more people will wake up to the anti-science agenda so many are peddling in this country."
"Can I Take Your Son to Church?"
  • Religious people try to get children young... even if their parents are atheists. C.f. Dawkins' "Good and Bad Reasons for Believing": religious people were "told to believe [crazy claims] when they were young enough to believe anything."
"Publish Less, Perish More"
  • "What if we did a little more thinking and a little less sharing? What if a publication was thoroughly peer reviewed? But there’s no time for this, right? Everyone is too busy, right? There’s the rub. We’d have the time to check our research if we stop shotgunning our whims at every conference with two legs and a skimpy dress. Suddenly, we’d see the ridiculous page limit requirements relax. We’d no longer have to fit complex talks into 12.225 minutes. Most importantly, we might start to understand what the hell other people are talking about. Fancy that, a presentation outside your narrow niche that you can follow?"
"The Courthouse Ring: Atticus Finch and the limits of Southern liberalism"
  • Malcolm Gladwell's most recent piece. I can't say I like it very much, but here it is anyway.

Thursday, September 17, 2009

Skeptics Circle #119

The 119th edition of the Skeptics Circle is out at Cubik's Rube. Posts to check out: The Skeptical Teacher's account of skeptrack at Dragon*Con, weird things on Kurzweil's bollocks live-forever stuff, Effort Sisyphus on how skeptics are (probably) immune to scams, and negative entropy on how foot detox machines are nonsense.

Wednesday, September 16, 2009

Technology Quarterly

The Economist released their latest Technology Quarterly a while back, here are my belated picks:
  • Attack of the drones (on the continued development of unmanned aircraft for surveillance and combat).
  • 3D TV (much to my surprise, it seems 3D television may be coming our way soon).
  • Air powered batteries (a new type of battery that uses oxygen from the atmosphere to charge itself so it can be much smaller and apparently it'll be cheaper too).
  • AI and CAPTCHA's (argues CAPTCHA's are safe from wannabe Skynets. For now). 
  • A factory on your desk (from 3D printers to Matter Compilers. Maybe). 
  • Biohacking (the rise of amateur tinkering with biological systems). 

Monday, September 14, 2009

Encephalon #75

Welcome to the 75th edition of Encephalon, your bi-monthly round-up of the best neuroscience and psychology posts from around the intertoobies...

First up in this edition is Vaughn over at Mind Hacks, with two fantastic titbits: amazing brain scans of 500-year-old mummies and a case-study of a patient who had a nail hammered into her head by some quack in an attempt to treat persistent headaches.

The massive literature on how human cognition is affected by non-rational, largely sub-conscious and often unacknowledged biases continues to grow. Two contributors submitted posts in this general area: Dave of Cognitive Daily and Dave of Neuronarrative. Our first Dave covers some recent work on how mood affects memory: apparently being in a bad mood when trying to memorize a list of words nullifies some kind of category cross-talk and thus improves recall. Weird. Our second Dave submitted two posts: the first (c'mon, parse that...) covers further work on how memories can be manipulated (this time courtesy of video), and the second is on how temperate influences emotion.

While neither Mo at Neurophilosophy nor Ed at Not Exactly Rocket Science actually submitted to the carnival, they produced a gem of a post apiece so I thought it appropriate to include them: Mo on the 'fiber optics' of the vertebrate retina and Ed on the dance of the disembodied gecko tail.

Daniel and Greg at Neuroanthropology do some public service blogging with a three part take down of a bad study of Rule 34 ("if it exists, there's porn on it"). Part 1: Sex, lies and IRB Tape, Part II: SurveyFail redax, and Part III: Nature/Nurture: Slash to the rescue...

So how about some neuroscience? Andrew and Scicurious to the rescue... The latter discusses behavioral tagging as a mechanism for long-term memory formation, and the former has a post on how adult fear memories can be erased (well, in rats).

Brain Blogger submitted two pieces: Jared Tanner calls for ethical debate before we create an artificial brain and Meghan Meyer discusses how physical and social pain may share neural architecture.

Finally, the usual trifecta of posts from Sharp Brains: cognitive enhancement via both neuropsychology and pharmacology, working memory training vs. medication treatment for children with ADHD, and a retooled understanding of 'use it or lose it'.

The next edition of the carnival, as far as I can see, has not been scheduled, so email Alvaro to volunteer!

Thursday, September 10, 2009

Quote: Carl Sagan

I just finished reading Carl Sagan's skeptical classic, The Demon-Haunted World and I found a lot of quotable material. Here's just one, in the context of the European witch hunts:
If we’re absolutely sure that our beliefs are right, and those of others wrong; that we are motivated by good, and others by evil; that the king of the universe speaks to us, and not to adherents of very different faiths, that it is wicked to challenge conventional doctrines or to ask searching questions; that our main job is to believe and obey – then the witch mania will recur in its infinite variations down to the time of the last man.

Video: Smoke Ring Collision

So this video (embedded below, or click here) has nothing to do with my blog, but it's too awesome to pass up. Apparently, it's what physicists do when they're high...

Lazy Linking

This week's lazy linking...

"Winners wear red: How colour twists your mind"
  • A genuinely superb article in New Scientist on yet another crazy psychological bias: seeing red. It seems red is a phylogenetically conserved signal of danger/threat that subtly but significantly affects cognition and behavior in a range of animals, including humans. I have to wonder: does this effect explain part of Britian's dominance in the 19th century? Did the red of the Redcoats influence the outcome of the Battle of Waterloo? (Which, as Wellington said, was "the nearest run thing you ever saw". Apparently, "damn close run thing" is a misquotation).
"Homeopathic Rebuttal: The argument is in there, bit it's at homeopathic dilutions"
  • Angela Butterworth responds to an attack on her by a local homeopath.
  • Ben Goldacre making sense on medical patents.
  • "If the global $550bn pharmaceutical industry are trying to make an economic case for patents in the developing world, then they must argue that the benefit to drug development from the financial incentives in these tiny corners of the world market is so significant – so vital, the final link in the incentive chain – that it is more important than millions of unnecessary deaths. I am not a health economist, but I doubt that is a fair swap, and this is not what patent laws were invented for."
  • A piece on the open courseware movement and what it means. (Via Michael Nielsen).
"The logic of skepticism"
  • Massimo Pigliucci on the philosophical and statistical groundwork of modern (scientific) skepticism.
  • "So when trying to steer the course between skepticism and gullibility, it makes sense to stay much closer to the Scylla of skepticism than to bring our ship of beliefs within reach of the much larger and more menacing Charybdis of gullibility. The net result of this prudent policy, however, is that even positive skeptics are bound to reject a lot of beliefs, with the side effect that their popularity plunges. As I said, it’s a lonely art, but you can take comfort in the psychological satisfaction of being right much more often than not. This will not get you many girls and drinking buddies, though."
"Unicolonial Ants Pose Challenge to "Selfish Gene" Theory"
  • Excellent and thought provoking piece on recent ant research that seems to support group selection. I don't know whether it's right, but I do know it's interesting and important.

Tuesday, September 8, 2009

Chameleons DO change their color to blend in with their environment

For reasons that are not to hard to fathom, myths about chameleons abound. The Victorians thought they lived entirely on air; a common Zulu superstition is that they're evil (as I confirmed for myself a while back when I tried to show a chameleon I had caught to our gardener); and, more recently, I've been hearing a lot of people say chameleon color changing has nothing to do with camouflage. Even Cracked has got in on the act with an article on "bullshit animals facts", which argues a chameleon's color is determined largely by its mood. I call bullshit on their bullshit.

Thanks to frequent childhood visits to a family farm, I've had lots of encounters with these amazing critters and I've seen them change color to blend in with their environment with my own eyes. Not particularly good evidence, I hear you say. Agreed, so I spent 2 minutes on Wikipedia, followed a link, and found this New Scientist piece, about this study in Biology Letters. And guess what? At least one species of chameleon, Smith's dwarf chameleon (which, incidentally, is South African), does change color to camouflage itself from predators. The paper, "Predator-specific camouflage in chameleons" by Stuart-Fox et. al., demonstrated in several behavioral trials that these chameleons engage in background matching when presented with model predators. In other words, these guys do their best to blend in with their environment when they encounter things that want to eat them. (You can see a clear example of a chameleon matching its background in this YouTube clip [Note: James informs me in the comments that this might be fake]).

So why do people think chameleon camouflage is a myth? It seems other research (also by Stuart-Fox) that concluded color changing evolved for social signalling has been misinterpreted. The conclusion of this second paper was: "our results suggest that selection for conspicuous social signals drives the evolution of colour change in this system, supporting the view that transitory display traits should be under strong selection for signal detectability." In other words, the primary evolutionary 'function' of color changing in chameleons seems to be social signalling. But it does not follow from this that chameleons cannot also use color changing for crypsis -- the ability may have evolved for social signalling, but nothing stops it from being exapted for camouflage. It is such an obvious evolutionary trick that I'm surprised anyone interpreted Stuart-Fox et. al. second paper in this way. If you already have a visual system (to detect background color), you can already change color, you suffer predation and camouflage thus increases fitness, we should positively expect exaptation for crypsis.

As I also pointed out on my fox domistication piece, I'm not a biologist so you should be especially skeptical of my opinions on this (though, I managed to convince biologist Richard Glor over at Dechronization that my interpretation is right). But still... At least some chameleons change their color to blend in with their environment. Obviously.

UPDATE: I emailed Stuart-Fox and asked whether my take is correct. Here is the reply in part (my emphasis):
Yes, your interpretation is correct. Colour change in chameleons serves multiple current functions including camouflage (background matching), thermoregulation and communication (courtship and male-male contests). But we need to distinguish current functions from the selective pressures driving the evolution of the abiltiy to change colours. Some species can change colours much more than others - the question I was trying to answer is why such variation? And it seems that sexual selection for communication (signalling) is the most important selective pressure because the species that change colour the most have the most conspicuous colour patterns that they use to communicate.
Stuart-Fox D, Moussalli A, & Whiting MJ (2008). Predator-specific camouflage in chameleons. Biology letters, 4 (4), 326-9 PMID: 18492645

Stuart-Fox D, & Moussalli A (2008). Selection for social signalling drives the evolution of chameleon colour change. PLoS biology, 6 (1) PMID: 18232740

Thursday, September 3, 2009

Skeptics Circle #118

The 118th edition of the Skeptics Circle is out at The Evolving Mind. Posts to check out: SkeptVet on nutritional nonsense about pet food, The Bronze Blog on how as citizens of "Middle World" our intuitions fool us into thinking quantum mechanics is magic, Cubik's Rube on alternative medicine, and The Mad Skeptic on woo in the bedroom.

Good news on quackery

Two pieces of unrelated good news about alternative medicine in South Africa and the developing world...

First, a couple of weeks ago the Voice of Young Science (part of the British Sense About Science charity) wrote an open letter to the World Health Organization to ask it to issue clear guidelines on the use of homeopathic preparations for five serious diseases. The WHO has now responded by saying it does NOT recommend homeopathy for the treatment of HIV, TB, malaria, influenza or infant diarrhea. The Voice of Young Science has written to health ministers (pdf) informing them of the WHO's position.

Second, as the Treatment Action Campaign reports, the Advertising Standards Authority of Southern Africa (ASA) has ruled in favor of a complaint against a company selling a herbal remedy called Revivo advertized as a cure for HIV and AIDS. This is great news -- skeptics should make an effort to issue more complaints, and hopefully ASA will continue to side with science.

Lazy Linking

"Homeopathy and Evidence-Based Medicine: Back to the Future" -- Part I, Part II, Part III, Part IV and Part V.
  • Kimball Atwood's superb series over at Science-Based Medicine on homeopathy. He argues convincingly in the final post that evidence-based medicine ought to include prior probability -- alternative modalities like homeopathy that violate well established laws of physics should be at the back of the queue for testing in clinical trails. 
"Animal Behavior: Going to the Dogs" (Gated)
  • Very interesting news feature in Science on how dogs are quickly becoming the favored model animal for research in social cognition. (It's also discussed in their free podcast).
"Baby Bear's lament: James Wood in the New Yorker"
  • Phyrangula is the most popular science blog in the world and this piece nicely illustrates why. It's PZ at his funny and irreverent best. Richard Dawkins even shows up in the comments and compares PZ to Peter Medawar... 
"An Update on C. P. Snow's "Two Cultures""
  • Lawrence Krauss reinterprets the "Two Cultures" analysis.
  • "Until we are willing to accept the world the way it is, without miracles that all empirical evidence argues against, without myths that distort our comprehension of nature, we are unlikely to bridge the divide between science and culture and, more important, we are unlikely to be fully ready to address the urgent technical challenges facing humanity."
  • Natalie Angier on female sexual psychology. She discusses recent research that suggests a desire for multiple partners increases a woman's fitness.
"Why are atheists so disliked?"
  • The answer, at least according to research Epiphenom reviews, is that atheists are distrusted. Luckily, there is evidence that when religious people find out how prevalent atheism is, their distrust disappears. All the more reason to support the Out Campaign.

Wednesday, September 2, 2009

Silver fox domestication

I recently linked to an extract from Richard Dawkins’ new book in which he mentions a fascinating long-term experiment on silver foxes. The short version: starting in the late 1950s, the Russian geneticist Dmitry Belyaev selectively bred a population of silver foxes for tameness, and, surprisingly, they acquired a dog-like morphology as a by-product (floppy ears, turned-up tails, and so on). In other words, determining which foxes got to breed based solely on how tame and friendly they were produced not only successively tamer foxes, but dog-like physical traits as well. Belyaev believed (and Dawkins concurs) that the reason for this link is pleiotropy, the phenomenon of a single gene having multiple and seemingly unconnected phenotypic effects. As Lyudmila Trut, Belyaev’s successor as head of the Institute of Cytology and Genetics, explains (pdf):
Behavioral responses, [Belyaev] reasoned, are regulated by a fine balance between neurotransmitters and hormones at the level of the whole organism. The genes that control that balance occupy a high level in the hierarchical system of the genome. Even slight alterations in those regulatory genes can give rise to a wide network of changes in the developmental processes they govern. Thus, selecting animals for behavior may lead to other, far-reaching changes in the animals’ development. Because mammals from widely different taxonomic groups share similar regulatory mechanisms for hormones and neurochemistry, it is reasonable to believe that selecting them for similar behavior—tameness—should alter those mechanisms, and the developmental pathways they govern, in similar ways.
Now, this may be entirely correct but I can think of a fairly obvious alternative explanation: subtle biases in the researchers that meant the foxes were not really selected based purely on tameness. (A bit like Clever Hans in reverse). There is an Olympus Mons-sized literature on how human decision-making is influenced, entirely subconsciously, by a dizzying array of crazy things. To take one random example (also previously linked to), holding a heavier clipboard affects judgments of value and importance. Given the ubiquity of such latent biases, are we really to believe that some mutation (unconnected behavior) that merely made the affected fox look tame – made it look a bit more like a dog, say – didn't influenced judgments of tameness? To flesh this thought out a bit more, consider how the foxes were classified. Trut again:
At seven or eight months, when the foxes reach sexual maturity, they are scored for tameness and assigned to one of three classes. The least domesticated foxes, those that flee from experimenters or bite when stroked or handled, are assigned to Class III… Foxes in Class II let themselves be petted and handled but show no emotionally friendly response to experimenters. Foxes in Class I are friendly toward experimenters, wagging their tails and whining. In the sixth generation bred for tameness we had to add an even higher-scoring category. Members of Class IE, the “domesticated elite,” are eager to establish human contact, whimpering to attract attention and sniffing and licking experimenters like dogs. 
Class III seems unambiguously defined and it’s likely pretty straightforward to spot animals that belong to this category. The differences between the other classes, though, are significantly more subjective, and thus liable to all sorts of subtle biases. What, exactly, is an ‘emotional or friendly response to an experimenter’? What, exactly, is ‘eagerness to establish human contact’? It seems entirely possible – indeed likely – that animals that just looked tamer, had stereotypically domesticated features, were more likely to be assigned to Class I than to class II. If so, the foxes were not really selectively bred for “tameness and tameness alone”. No matter how scrupulous and honest the experimenters tried to be, I find it very hard to believe that they succeeded, continuously and without fail, to assign animals objectively to categories. Indeed, the researchers working on the foxes (including Trut) outlined a new scoring method in a 2007 paper, in which they admitted that a cross-breeding experiment “clearly demonstrates that the traditional scoring systems established for selection of foxes for behavior has limited resolution for measuring behavior as a continuous variable”. Assuming, as seems likely, that tameness-aggressiveness forms a continuous behavioral axis, we cannot be confident that Belyaev and his colleagues invariably selected for tameness alone. If this is correct, the pleiotropy story is somewhat undermined, though by no means refuted, of course. It seems significant, however, that the alternative explanation is more parsimonious: it need not posit nearly infallible experimenters, nor a priori unlikely pleiotropic linkages.

Of course, I’m no expert on this topic, so maybe I’ve misunderstood the protocols, or perhaps the alternative I sketch was been refuted somewhere in the literature. I would, however, be very interested to find out how the researchers ruled out this alternative hypothesis...

Trut, L. (1999). Early Canid Domestication: The Farm-Fox Experiment American Scientist, 87 (2) DOI: 10.1511/1999.2.160

Kukekova, A., Trut, L., Chase, K., Shepeleva, D., Vladimirova, A., Kharlamova, A., Oskina, I., Stepika, A., Klebanov, S., Erb, H., & Acland, G. (2007). Measurement of Segregating Behaviors in Experimental Silver Fox Pedigrees Behavior Genetics, 38 (2), 185-194 DOI: 10.1007/s10519-007-9180-1

Tuesday, September 1, 2009

Picture: Fun with homeopathy

I just can't resist posting the following, courtesy of Hell's News Stand.:

(Via Science-Based Medicine).

Fun with a local homeopath

Note: Prinsloo has edited his website in light of our criticisms, but the version of his site that I responded to is still available on Google cache. 

A Pretoria-based homeopath, one Dr. JP Prinsloo, has taken on some local skeptics, including Owen and Angela. I'll have more to say about him in the next while, but for the moment I want to do three things: point to Owen's superb (and damn funny) response, address one of Prinsloo's arguments and demonstrate he misinterprets the medical literature on homeopathy.

In a section of his website "Answering the Skeptics", Prinsloo makes the follow argument:
Let me begin this page by stating quite emphatically that;

It is against my principles to debate the validity and efficacy of Homeopathy with ignorants (sic).

On this page, reference to the word ignorant (sic) shall mean: Any so-called scientist or "expert" that expresses him/herself on the subject of Homeopathy, it's validity or efficacy, but who -

* Is not a qualified Homeopath;
* Has not studied Homeopathy to the extent that a Homeopath does;
* Has not conducted extensive research on Homeopathy in accordance with the scientific principles of Homeopathy under the supervision of a qualified Homeopath;
* Does not possess sufficient experience in the practical application of Homeopathy in a clinical setting;
* Who is not registered as a Homeopathic Practitioner in South Africa and / or does not meet the requirements for such registration;
* Who is not an expert on applied Homeopathy.(*)

With respect to Homeopathy, that is an ignorant (sic) in my opinion and someone not worthy of my time.

(*) Howard Stephen Berg, The World's Fastest Reader, defines an expert as "someone who has read at least 25 books on a particular subject".
This is a really bad argument. But first, even if we accept these absurd requirements, there is a person who, as a former homeopath, fulfills these criteria and is nevertheless a prominent and respected critic thereof: Edzard Ernst. The key point, though, is that people self-select into homeopathy, so saying only homeopaths are qualified to say anything about it is a transparent attempt to shield it from criticism. Are only astrologers possibly qualified to say anything about astrology? Shall we dismiss all criticisms of parapsychology unless it comes from a qualified parapsychologist? Am I an ignorant (sic) for dismissing the flat earth theory despite not having read 25 books about it? Of course not; doing so would unnecessarily cede the field to the woos. Prinsloo simply misunderstands how and when to defer to experts. (A topic I'm currently writing a lengthy post about, by the way). Furthermore, the most relevant question about homeopathy is: does it work? Do large well-designed double-blind placebo-controlled trails demonstrate that it has a statistically significant clinically significant effect? That is, when you take care not to fool yourself, does homeopathy work? (Hint: the answer is no). And, as Simon also points out in a comment to Owen's post, the most relevant expertise in answering that question is in research methodology and medical statistics. Is Prinsloo a qualified medical statistician? Has he read 25 books on medical research methods and statistics?

Prinsloo also manifestly misunderstands the medical literature. (Alternatively, he's a lair -- but that would be uncharitable. Keep Hanlon's Razor always in mind). In "Homeopathy in Perspective" (based on a journal article of Prinsloo's apparently), he states:
A state of the art meta analysis reviewed 186 studies, 89 of which fit pre-defined criteria, showed that patients taking homeopathic medicines were 2.45 times more likely to experience a positive therapeutic effect than placebo.(19)
Sounds promising. So let's follow the reference, shall we? "Are the clinical effects of homoeopathy placebo effects?" (The Lancet, 2005). Prinsloo has a slight problem: this study simply doesn't conclude what he says it does. Here is an excerpt from the Discussion section:
We assumed that the effects observed in placebo-controlled trials of homoeopathy could be explained by a combination of methodological deficiencies and biased reporting. Conversely, we postulated that the same biases could not explain the effects observed in comparable placebo-controlled trials of conventional medicine. Our results confirm these hypotheses: when analyses were restricted to large trials of higher quality there was no convincing evidence that homoeopathy was superior to placebo, whereas for conventional medicine an important effect remained. Our results thus provide support for the hypothesis that the clinical effects of homoeopathy, but not those of conventional medicine, are unspecific placebo or context effects.
Prinsloo continues:
Another meta-analysis reviewed 107 studies of homeopathic medicines, 81 of which (77%) showed positive effect. Of the best 22 studies, 15 showed efficacy. The researchers concluded: "The evidence presented in this review would probably be sufficient for establishing homeopathy as a regular treatment for certain indications." Further, "The amount of positive evidence even among the best studies came as a surprise to us." (20) 
And what is this meta-analysis (sic)? "Clinical Trials of Homeopathy" (BMJ, 1991). Prinsloo does report accurately on the details, but then conveniently ignores the authors' conclusion: "At the moment the evidence of clinical trials is positive but not sufficient to draw definitive conclusions because most trials are of low methodological quality and because of the unknown role of publication bias." (It continues to say that there is a legitimate case for further research). Nor does Prinsloo mention that this study (which was a systematic review, not a meta-analysis) has subsequently been rubbished. The positive result in this study, it seems fair to conclude, was due to inappropriate weightings of trail quality (the exclusion of peer-review, for one) and biased selection. Moreover, subsequent better designed systematic reviews (like this one by Ernst) have concluded "there was no homeopathic remedy that was demonstrated to yield clinical effects that are convincingly different from placebo".

More on Prinsloo later...

Shang, A., Huwiler-Müntener, K., Nartey, L., Jüni, P., Dörig, S., Sterne, J., Pewsner, D., & Egger, M. (2005). Are the clinical effects of homoeopathy placebo effects? Comparative study of placebo-controlled trials of homoeopathy and allopathy The Lancet, 366 (9487), 726-732 DOI: 10.1016/S0140-6736(05)67177-2