5X5 Episode 77

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5X5 Episode 110
Naturalistic Fallacy
11th April 2012
5X5 76	5X5 78
Skeptical Rogues
S: Steven Novella
R: Rebecca Watson
B: Bob Novella
J: Jay Novella
E: Evan Bernstein
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The Double-Blind Protocol in Science

Voice-over: You're listening to the Skeptics' Guide 5x5, five minutes with five skeptics, with Steve, Jay, Rebecca, Bob and Evan.

S: This is the SGU 5x5 and tonight we are talking about double blind testing. The double blind refers to a protocol in scientific studies in which both the examiner (the researcher) and the subject do not know critical details about the study itself. Specifically if we use for example a medical test, the subject receiving the treatment doesn't know if they are getting a real treatment or a placebo a fake treatment. And the person examining them to figure out how they are responding to the treatment also does not know if they received the real treatment or the placebo. The purpose for blinding is to control for variables in the study, just like science is always about controlling for variables, by doing this you eliminate all of the psychological and bias and expectation variables and you isolate the treatment itself or whatever, whatever is the subject of the scientific experiment.

E: And ah one of the earliest suggestions that a blinded approach to doing experiments would be handy or valuable came from Claude Bernard who was once named one of the greatest men of all science. He was a physiologist from the mid-nineteenth century and he recommended that any scientific experiment should be split between the theorist who conceived the experiment and a naive observer who registers the results without foreknowledge of the theory or hypothesis that's being tested, and this suggestion was in stark contrast to the enlightenment area attitude that scientific observation can and should only be valid when it was undertaken by someone who was well educated and an informed scientist. So this was pretty much opposite of that mind set and it turned out to be revolutionary.

J: A good example of double blinding involved forensics, specifically criminal identification. Often a police officer will show a witness pictures of people in hopes the main suspect will be picked. We have all seen that scenario played out over and over in many different TV shows and movies. This is a single blind test. the problem is that the officer could unknowingly steer the witness to the preferred suspect by the way he talks by the way even the hand gestures and all these subtle queues that the officer might not realize that he is giving to the witness. Therefore it is becoming more common nowadays to do double blind identification by bringing in an officer that is unfamiliar with the case to show the pictures to the witness which would then prevent any of these subtle ques from coming through because this police officer doesnt know who the primary suspect is so he cant unconciously que who it is.

R: a good example of something that we could have investigated better if people looked a the placebo effect is the clever hahns phenomenon in which people thought that a horse could do math just by tapping out his hoof, which we've covered in the past on SGU. and what it turned out to be was that the man who owned the horse was giving the horse subtle queues as to what point to stop tapping his hoof. for instance someone from the audience would say what is 3+2 the horse would tap out 5 beats and uh even the person who owned the horse thought that he was for real. He didn't realize that he was giving the horse the subtle clue as to what point to stop tapping. If that experiment had been double blinded then they could have ruled out the experimenters own bias that was unconsciously influencing the experiment and they would have seen that it was actually that that was causing clever hahns to stop tapping his little hoof.

J: You know double blind experiments don't only apply to scientists in a laboratory, you could do this at school like say you are performing some type of experiment in science class like the absorption of paper towels of different paper towels. you could use the double blind protocol in your experiment and see how the results are different when you use it versus when you don't use it.

S: That's right and it does apply also out of uh not just in medicine which i think is the context that people most readily think of. For example N rays, N rays were all the rage back in 1903 after xrays were discovered other researchers thought they had discovered another kind of ray called N rays but they could only be seen under certain conditions by certain people. they were not observing it ina blinded way when the n rays were supposed to see them

S: SGU 5x5 is a companion podcast to the Skeptics' Guide to the Universe, a weekly science podcast brought to you by the New England Skeptical Society in association with skepchick.org. For more information on this and other episodes, visit our website at www.theskepticsguide.org. Music is provided by Jake Wilson.