Can you outsmart this logical fallacy? - Alex Gendler
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0:07 - 0:08Meet Lucy.
-
0:08 - 0:10She was a math major in college,
-
0:10 - 0:14and aced all her courses in probability
and statistics. -
0:14 - 0:18Which do you think is more likely: that
Lucy is a portrait artist, -
0:18 - 0:23or that Lucy is a portrait artist
who also plays poker? -
0:23 - 0:28In studies of similar questions, up to 80
percent of participants -
0:28 - 0:30chose the equivalent
of the second statement: -
0:30 - 0:34that Lucy is a portrait artist
who also plays poker. -
0:34 - 0:38After all, nothing we know about Lucy
suggests an affinity for art, -
0:38 - 0:42but statistics and probability
are useful in poker. -
0:42 - 0:45And yet, this is the wrong answer.
-
0:45 - 0:47Look at the options again.
-
0:47 - 0:50How do we know the first statement
is more likely to be true? -
0:50 - 0:54Because it’s a less specific version
of the second statement. -
0:54 - 0:58Saying that Lucy is a portrait artist
doesn’t make any claims -
0:58 - 1:02about what else she might or might not do.
-
1:02 - 1:07But even though it’s far easier to imagine
her playing poker than making art -
1:07 - 1:08based on the background information,
-
1:08 - 1:13the second statement is only true if she
does both of these things. -
1:13 - 1:17However counterintuitive it seems
to imagine Lucy as an artist, -
1:17 - 1:23the second scenario adds another condition
on top of that, making it less likely. -
1:23 - 1:28For any possible set of events, the
likelihood of A occurring -
1:28 - 1:33will always be greater than the likelihood
of A and B both occurring. -
1:33 - 1:37If we took a random sample of a million
people who majored in math, -
1:37 - 1:42the subset who are portrait artists might
be relatively small. -
1:42 - 1:44But it will necessarily be bigger
-
1:44 - 1:47than the subset who are portrait artists
and play poker. -
1:47 - 1:51Anyone who belongs to the second group
will also belong to the first– -
1:51 - 1:52but not vice versa.
-
1:52 - 1:58The more conditions there are,
the less likely an event becomes. -
1:58 - 2:02So why do statements with more conditions
sometimes seem more believable? -
2:02 - 2:06This is a phenomenon known as
the conjunction fallacy. -
2:06 - 2:09When we’re asked to make quick decisions,
we tend to look for shortcuts. -
2:09 - 2:12In this case, we look for what seems
plausible -
2:12 - 2:15rather than what is statistically
most probable. -
2:15 - 2:20On its own, Lucy being an artist doesn’t
match the expectations -
2:20 - 2:22formed by the preceding information.
-
2:22 - 2:25The additional detail about
her playing poker -
2:25 - 2:28gives us a narrative that resonates
with our intuitions— -
2:28 - 2:30it makes it seem more plausible.
-
2:30 - 2:35And we choose the option that seems more
representative of the overall picture, -
2:35 - 2:38regardless of its actual probability.
-
2:38 - 2:41This effect has been observed
across multiple studies, -
2:41 - 2:45including ones with participants
who understood statistics well– -
2:45 - 2:48from students betting on
sequences of dice rolls, -
2:48 - 2:53to foreign policy experts predicting
the likelihood of a diplomatic crisis. -
2:53 - 2:58The conjunction fallacy isn’t just a
problem in hypothetical situations. -
2:58 - 3:01Conspiracy theories and false news stories
-
3:01 - 3:05often rely on a version of the conjunction
fallacy to seem credible– -
3:05 - 3:09the more resonant details are added
to an outlandish story, -
3:09 - 3:12the more plausible it begins to seem.
-
3:12 - 3:15But ultimately, the likelihood
a story is true -
3:15 - 3:20can never be greater than the probability
that its least likely component is true.
- Title:
- Can you outsmart this logical fallacy? - Alex Gendler
- Speaker:
- Alex Gendler
- Description:
-
View full lesson: https://ed.ted.com/lessons/can-you-outsmart-this-logical-fallacy-alex-gendler
Meet Lucy. She was a math major in college, and aced all her courses in probability and statistics. Which do you think is more likely: that Lucy is a portrait artist, or that Lucy is a portrait artist who also plays poker? How do we know which statement is more likely to be true? Alex Gendler explores our tendency to look for shortcuts and the phenomenon known as the conjunction fallacy.
Lesson by Alex Gendler, directed by Artrake Studio.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 03:21
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