Monday, 14 April 2014

Teapots, Dilutions and Infrasound: The Negative Proof Conundrum

We can't prove negatives. If I tell you that there's a teapot orbiting Earth, and you can't provide evidence that there isn't, it doesn't mean that I'm right, or that there's a 50/50 chance that I'm right. The philosopher Bertrand Russell used this celestial teapot as an example of the 'burden of proof' - those making a claim need to support that claim with evidence. It's not incumbent on critics to produce evidence of the opposite.


Two groups promoting claims in the world of medicine had their theories assessed by the National Health and Medical Research Council (NHMRC): homeopaths and anti-wind groups. The NHMRC found no evidence to support their claims.

This absence of evidence was twisted into vindication, rather than incrimination. This is due to the common misunderstanding that if there is no evidence for something, the probabilities of that claim either being correct or incorrect are precisely equal.

Homeopathy

'Homoeopathy' is based around the idea that water has a 'memory', and consequently, you can treat someone using absurdly tiny amounts of whatever it is that caused their ailment ("like cures like"). The quantity of active ingredient in homeopathic products is insanely small.

In homeopathy, the smaller the quantity of the active ingredient, the more potent the medicine is said to be. This is bonkers.
Source: http://www.ritecare.com/homeopathic/guide_potency.asp
Last week, the NHMRC released an evidence review examining the efficacy of homeopathy, which found that:
"There is no reliable evidence that homeopathy is effective for treating health conditions" 
The Australian Homeopathic Association (AHA) responded in an interview on ABC News 24 - you can watch the full thing here, but one remark was quite relevant. The head of the AHA said the following, when asked about the NHMRC report on homeopathy:
“What I think you could fairly say is that what the NHMRC have presented does not say that homeopathy does not work or cannot work, but that the evidence might not be particularly strong in certain areas, or that their might not be enough of it”

Wind Turbine Syndrome 

A similar NHMRC evidence review into wind farms and health was released a few weeks back. They state: 
"There is no reliable or consistent evidence that wind farms directly cause adverse health effects in humans"
This matches the results of a 2010 evidence review that did essentially the same thing. In a letter to the then-Prime Minister Julia Gillard, CEO of the 'Waubra Foundation' Sarah Laurie wrote: 
"The current CEO of the NHMRC, Professor Warwick Anderson made it clear there was a concern, in his oral evidence to the Senate Inquiry, on 31st March 2011. He stated “we do not say that there are no ill effects”, and acknowledged that there was very little existing evidence, and that the absence of evidence did not mean there was not a problem.

Why the inaction, when families are being forced from their homes, or elderly pensioners are left to “rot”?"
It's a line held firm by anti-wind groups. An absence of evidence is no barrier to claiming that wind turbines are things to fear, as stated again in this interview, after the release of yet another report, this one by the South Australian EPA, clearing wind farms of health impacts (emphasis mine):
"TIMOTHY MCDONALD: But I guess - you just made the claim that country people are being harmed by these wind farms, but at the same time you're saying that the research isn't there to show one way or the other. I'm just trying to reconcile those two points. 
SARAH LAURIE: Well they're reporting serious harm to their doctors. Their doctors are reporting harm, their psychologists are reporting harm. The individuals are reporting harm to a series of Senate inquiries and nothing is being done.
The fact that it's not getting in the peer reviewed published journals doesn't mean the harm isn't happening."
Some Claims Really Need Evidence

You can make any claim you want. But some claims need to be backed with evidence. If, for instance, you travel to a community considering a wind farm development, and you tell them that the wind farm is going to give them autism, one might expect there to be strong evidence in support of that claim, rather a simple absence of evidence against it.

Or, if someone with cancer needs treatment, and you tell them that magic water will heal them, simply throwing up your hands and saying 'welp, there's no evidence I'm wrong!' doesn't cut it.

Be Clear About The Burden of Proof

An irksome feature of the NHMRC's report into wind farms and health was the exclusion of social and psychological issues.

There's no consideration of the impact of lobby groups that exist outside academia or the medical profession, and consequently, aren't bound by the need for evidence. It's hard to skirt around the fact that despite there being no evidence for homeopathy or 'wind turbine syndrome', both claims have incredible cut-through, due largely to the fact that people accept those claims based on value systems and world-view, rather than quantity of evidence.

This might be something the NHMRC could consider in the future. It's inevitable that an established and quantified absence of evidence is no barrier to people travelling to a town and trying to instil fear of wind energy, or other people trying to sell magic water as a cure for cancer.

Why not understand and pre-empt this, when trying to arm the community against misinformation? 

2 comments:

  1. Once again you have hit the nail straight on the head with this piece ( does the impact of hammer on nail in Australia cause me to hear the infrasound here in Canada ? ) :)

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  2. The summary statement in the NHMRC information paper says it all "There were no health conditions for which there was reliable evidence that homeopathy was effective. No good-quality, well-designed studies with enough participants for a meaningful result reported either that homeopathy caused greater health improvements than a substance with no effect on the health condition (placebo), or that homeopathy caused health improvements equal to those of another treatment.".

    To have a look at some of the basic calculations, as beautifully outlined by Edzard Ernst (although no doubt I'll misquote, not having it in front of me, but I highly recommend his book too, as an aside), for there to reliably be even one active molecule remaining in a homeopathic preparation, you would need to have at least a thousand universes, or a pill so big it would reach from the Earth to the sun.

    Lewandowsky also writes well on the use and retention of misinformation.

    Oh the power of the Dunning-Kruger effect.

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