Can you outsmart the fallacy that fooled a generation of doctors? - Elizabeth Cox
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0:10 - 0:11Oh the humanity!
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0:14 - 0:16Ah... humanity...
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0:16 - 0:19It’s a trainwreck,
but I can’t look away. -
0:20 - 0:24It’s 1843, and a debate is raging
among physicians -
0:24 - 0:28about one of the most common
killers of women: childbed fever. -
0:28 - 0:32Childbed fever strikes
within days of giving birth, -
0:32 - 0:38killing more than 70% of those infected—
and nobody knows what causes it. -
0:38 - 0:42Obstetrician Charles Meigs has a theory.
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0:42 - 0:44Having observed abdominal inflammation
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0:44 - 0:46in patients who go on
to develop the fever, -
0:46 - 0:51he claims this inflammation
is the cause of childbed fever. -
0:51 - 0:55Much of the medical establishment
supports his theory. -
0:55 - 0:56Oh, come on!
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0:56 - 1:01They really leave me no choice
but to teach them some skepticism. -
1:13 - 1:14That’s better.
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1:15 - 1:22Now, Meigs, your argument is based
on a fallacy— the false cause fallacy. -
1:22 - 1:26Correlation does not imply causation:
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1:26 - 1:29When two phenomena regularly occur
together, -
1:29 - 1:34one does not necessarily
cause the other. -
1:34 - 1:40So you say women who have inflammation
also come down with childbed fever, -
1:40 - 1:44therefore the inflammation
caused the fever. -
1:44 - 1:47But that’s not necessarily true.
-
1:47 - 1:51Yes, yes, the inflammation comes first,
then the fever, -
1:51 - 1:55so it seems like the inflammation
causes the fever. -
1:55 - 2:00But by that logic, since babies
usually grow hair before teeth, -
2:00 - 2:04hair growth must cause tooth growth.
-
2:04 - 2:06And we all know that’s not true,
right? -
2:06 - 2:08Actually, don’t answer that.
-
2:08 - 2:12A couple of different things
could be going on here. -
2:12 - 2:17First, it’s possible that fever
and inflammation are correlated -
2:17 - 2:20purely by coincidence.
-
2:20 - 2:26Or, there could be a causal relationship
that’s the opposite of what you think— -
2:26 - 2:29the fever causes the inflammation,
-
2:29 - 2:32rather than the inflammation
causing the fever. -
2:32 - 2:39Or both could share a common
underlying cause you haven’t thought of. -
2:39 - 2:46If I may, just what do you think
causes inflammation? Nothing? -
2:46 - 2:50It just is? Really?
-
2:50 - 2:54Humor me for a moment in discussing
one of your colleague’s ideas— -
2:54 - 2:57Dr. Oliver Wendell Holmes.
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2:57 - 3:00I know, I know,
you don’t like his theory— -
3:00 - 3:03you already wrote
a scathing letter about it. -
3:03 - 3:06But let’s fill your students in, shall we?
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3:06 - 3:12Holmes noticed a pattern:
when a patient dies of childbed fever, -
3:12 - 3:15a doctor performs an autopsy.
-
3:15 - 3:19If the doctor then treats a new patient,
-
3:19 - 3:23that patient often comes
down with the fever. -
3:23 - 3:24Based on this correlation
-
3:24 - 3:29between autopsies of fever victims
and new fever patients, -
3:29 - 3:32he proposes a possible cause.
-
3:32 - 3:39Since there’s no evidence that the autopsy
causes the fever beyond this correlation, -
3:39 - 3:44he doesn’t jump to the conclusion
that autopsy causes fever. -
3:44 - 3:49Instead, he suggests that doctors
are infecting their patients -
3:49 - 3:55via an invisible contaminant
on their hands and surgical instruments. -
3:55 - 4:01This idea outrages most doctors,
who see themselves as infallible. -
4:01 - 4:05Like Meigs here, who refuses
to consider the possibility -
4:05 - 4:08that he’s playing a role
in his patients’ plight. -
4:08 - 4:14His flawed argument doesn’t leave any
path forward for further investigation— -
4:14 - 4:16but Holmes’ does.
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4:24 - 4:27It’s 1847, and physician Ignaz Semmelweis
-
4:27 - 4:30has reduced the number
of childbed fever deaths -
4:30 - 4:35in a clinic from 12% to 1%
by requiring all medical personnel -
4:35 - 4:40to disinfect their hands after autopsies
and between patient examinations. -
4:40 - 4:45With this initiative, he has proven
the contagious nature of childbed fever. -
4:46 - 4:47Ha!
-
4:50 - 4:54It’s 1879, and Louis Pasteur
has identified -
4:54 - 4:58the contaminant responsible
for many cases of childbed fever: -
4:58 - 5:01Hemolytic streptococcus bacteria.
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5:04 - 5:07Hmm, my fries are cold.
-
5:07 - 5:11Must be because my ice cream melted.
- Title:
- Can you outsmart the fallacy that fooled a generation of doctors? - Elizabeth Cox
- Speaker:
- Elizabeth Cox
- Description:
-
View full lesson: https://ed.ted.com/lessons/can-you-outsmart-the-fallacy-that-fooled-a-generation-of-doctors-elizabeth-cox
It's 1843, and a debate is raging about one of the most common killers of women: childbed fever— no one knows what causes it. One physician has observed patients with inflammation go on to develop childbed fever, and therefore believes the inflammation causes the fever. What's the problem with this argument? Elizabeth Cox explores the false cause fallacy and how to dissect claims with skepticism.
Lesson by Elizabeth Cox, directed by TOGETHER.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:14
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Tara Ahmadinejad edited English subtitles for Can you outsmart the fallacy that fooled a generation of doctors? |