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  • ["Cars with flames painted on the hood might get more speeding tickets. Are the flames making the car go fast? No."- Barbara Kingsolver, Flight Behavior]

  • Oh the humanity!

  • Ah... humanity...

  • It's a train wreck, but I can't look away.

  • It's 1843, and a debate is raging among physicians about one of the most common killers of women: childbed fever.

  • Childbed fever strikes within days of giving birth, killing more than 70 percent of those infected, and nobody knows what causes it.

  • Obstetrician Charles Meigs has a theory.

  • Having observed abdominal inflammation in patients who go on to develop the fever, he claims this inflammation is the cause of childbed fever.

  • Much of the medical establishment supports his theory.

  • Oh, come on!

  • They really leave me no choice but to teach them some skepticism.

  • That's better.

  • Now, Meigs, your argument is based on a fallacythe false cause fallacy.

  • Correlation does not imply causation.

  • When two phenomena regularly occur together, one does not necessarily cause the other.

  • So you say women who have inflammation also come down with childbed fever, therefore the inflammation caused the fever.

  • But that's not necessarily true.

  • Yes, yes, the inflammation comes first, then the fever, so it seems like the inflammation causes the fever.

  • But by that logic, since babies usually grow hair before teeth, hair growth must cause tooth growth.

  • And we all know that's not true, right?

  • Actually, don't answer that.

  • A couple of different things could be going on here.

  • First, it's possible that fever and inflammation are correlated purely by coincidence.

  • Or, there could be a causal relationship that's the opposite of what you thinkthe fever causes the inflammation, rather than the inflammation causing the fever.

  • Or both could share a common underlying cause you haven't thought of.

  • If I may, just what do you think causes inflammation? Nothing?

  • It just is? Really?

  • Humor me for a moment in discussing one of your colleague's ideasDr. Oliver Wendell Holmes.

  • I know, I know, you don't like his theory, you already wrote a scathing letter about it.

  • But let's fill your students in, shall we?

  • Holmes noticed a pattern: when a patient dies of childbed fever, a doctor performs an autopsy.

  • If the doctor then treats a new patient, that patient often comes down with the fever.

  • Based on this correlation between autopsies of fever victims and new fever patients, he proposes a possible cause.

  • Since there's no evidence that the autopsy causes the fever beyond this correlation, he doesn't jump to the conclusion that autopsy causes fever.

  • Instead, he suggests that doctors are infecting their patients via an invisible contaminant on their hands and surgical instruments.

  • This idea outrages most doctors, who see themselves as infallible.

  • Like Meigs here, who refuses to consider the possibility that he's playing a role in his patients' plight.

  • His flawed argument doesn't leave any path forward for further investigation, but Holmes' does.

  • It's 1847, and physician Ignaz Semmelweis has reduced the number of childbed fever deaths in a clinic from 12% to 1% by requiring all medical personnel to disinfect their hands after autopsies and between patient examinations.

  • With this initiative, he has proven the contagious nature of childbed fever.

  • Ha!

  • It's 1879, and Louis Pasteur has identified the contaminant responsible for many cases of childbed fever: hemolytic streptococcus bacteria.

  • Hmm, my fries are cold.

  • Must be because my ice cream melted.

  • So, do you think you could do my job? Let's find out shall we? Click here to see if you can outsmart this fallacy.

["Cars with flames painted on the hood might get more speeding tickets. Are the flames making the car go fast? No."- Barbara Kingsolver, Flight Behavior]

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B2 UK TED-Ed fever inflammation fallacy correlation autopsy

Can you outsmart the fallacy that fooled a generation of doctors? - Elizabeth Cox

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    Minjane posted on 2020/08/11
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