Can you outsmart this logical fallacy? - Alex Gendler

2,032,642 views ใƒป 2019-11-25

TED-Ed


ืื ื ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ืœืžื˜ื” ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ.

ืชืจื’ื•ื: Ido Dekkers ืขืจื™ื›ื”: Allon Sasson
00:06
Meet Lucy.
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ืคื’ืฉื• ืืช ืœื•ืกื™.
00:08
She was a math major in college,
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ื”ื™ื ื‘ื•ื’ืจืช ืชื•ืืจ ืฉื ื™ ืœืžืชืžื˜ื™ืงื” ื‘ืžื›ืœืœื”,
00:09
and aced all her courses in probability and statistics.
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ื•ื”ืฆื˜ื™ื™ื ื” ื‘ื›ืœ ื”ืงื•ืจืกื™ื ื‘ื”ืกืชื‘ืจื•ืช ื•ืกื˜ื˜ื™ืกื˜ื™ืงื”.
00:14
Which do you think is more likely: that Lucy is a portrait artist,
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ืžื” ืืชื ื—ื•ืฉื‘ื™ื ืฉื™ื•ืชืจ ื”ื’ื™ื•ื ื™: ืฉืœื•ืกื™ ื”ื™ื ืืžื ื™ืช ืคื•ืจื˜ืจื˜ื™ื,
00:18
or that Lucy is a portrait artist who also plays poker?
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ืื• ืฉืœื•ืกื™ ื”ื™ื ืืžื ื™ืช ืคื•ืจื˜ืจื˜ื™ื ืฉื’ื ืžืฉื—ืงืช ืคื•ืงืจ?
00:23
In studies of similar questions, up to 80 percent of participants
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ื‘ืžื—ืงืจื™ื ืฉืœ ืฉืืœื•ืช ื“ื•ืžื•ืช, ืขื“ 80 ืื—ื•ื– ืžื”ืžืฉืชืชืคื™ื
00:27
chose the equivalent of the second statement:
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ื‘ื—ืจื• ื‘ืžืงื‘ื™ืœื” ืฉืœ ื”ื”ืฆื”ืจื” ื”ืฉื ื™ื”:
00:30
that Lucy is a portrait artist who also plays poker.
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ืฉืœื•ืกื™ ื”ื™ื ืืžื ื™ืช ืคื•ืจื˜ืจื˜ื™ื ืฉื’ื ืžืฉื—ืงืช ืคื•ืงืจ.
00:33
After all, nothing we know about Lucy suggests an affinity for art,
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ืื—ืจื™ ื”ื›ืœ, ืฉื•ื ื“ื‘ืจ ืžืžื” ืฉืื ื—ื ื• ื™ื•ื“ืขื™ื ืขืœ ืœื•ืกื™ ืœื ืžืฆื™ืข ื–ื™ืงื” ืœืืžื ื•ืช,
00:38
but statistics and probability are useful in poker.
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ืื‘ืœ ืกื˜ื˜ื™ืกื˜ื™ืงื” ื•ื”ืกืชื‘ืจื•ืช ื”ืŸ ืฉื™ืžื•ืฉื™ื•ืช ื‘ืคื•ืงืจ.
00:42
And yet, this is the wrong answer.
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ื•ืขื“ื™ืŸ, ื–ื• ื”ืชืฉื•ื‘ื” ื”ืฉื’ื•ื™ื”.
00:44
Look at the options again.
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ื”ืกืชื›ืœื• ื‘ืื•ืคืฆื™ื•ืช ืฉื•ื‘.
00:46
How do we know the first statement is more likely to be true?
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ืื™ืš ืื ื—ื ื• ื™ื•ื“ืขื™ื ืฉื”ื”ืฆื”ืจื” ื”ืจืืฉื•ื ื” ื™ื•ืชืจ ืกื‘ื™ืจื” ื›ืืžื™ืชื™ืช?
00:50
Because itโ€™s a less specific version of the second statement.
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ื‘ื’ืœืœ ืฉื–ื• ืื•ืคืฆื™ื” ืคื—ื•ืช ืกืคืฆื™ืคื™ืช ืฉืœ ื”ื”ืฆื”ืจื” ื”ืฉื ื™ื”.
00:54
Saying that Lucy is a portrait artist doesnโ€™t make any claims
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ืœื”ื’ื™ื“ ืฉืœื•ืกื™ ื”ื™ื ืืžื ื™ืช ืคื•ืจื˜ืจื˜ื™ื ืœื ืžืขืœื” ืฉื•ื ื˜ืขื ื”
00:58
about what else she might or might not do.
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ื‘ื ื•ื’ืข ืœืžื” ืขื•ื“ ื”ื™ื ื™ื›ื•ืœื” ืื• ืœื ื™ื›ื•ืœื” ืœืขืฉื•ืช.
01:01
But even though itโ€™s far easier to imagine her playing poker than making art
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ืื‘ืœ ืœืžืจื•ืช ืฉื”ืจื‘ื” ื™ื•ืชืจ ืงืœ ืœื“ืžื™ื™ืŸ ืื•ืชื” ืžืฉื—ืงืช ืคื•ืงืจ ืžืืฉืจ ื™ื•ืฆืจืช ืืžื ื•ืช
01:06
based on the background information,
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ื‘ื”ืชื‘ืกืก ืขืœ ืžื™ื“ืข ื”ืจืงืข,
01:08
the second statement is only true if she does both of these things.
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ื”ื”ืฆื”ืจื” ื”ืฉื ื™ื” ื ื›ื•ื ื” ืจืง ืื ื”ื™ื ืขื•ืฉื” ืืช ืฉื ื™ ื”ื“ื‘ืจื™ื.
01:13
However counterintuitive it seems to imagine Lucy as an artist,
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ืขื“ ื›ืžื” ืฉื–ื” ื ืจืื” ืœื ืื™ื ื˜ื•ืื™ื˜ื™ื‘ื™ ืœื“ืžื™ื™ืŸ ืืช ืœื•ืกื™ ื›ืืžื ื™ืช,
01:17
the second scenario adds another condition on top of that, making it less likely.
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ื”ืชืจื—ื™ืฉ ื”ืฉื ื™ ืžื•ืกื™ืฃ ืชื ืื™ ื ื•ืกืฃ ืขืœื™ื•, ืžื” ืฉืขื•ืฉื” ืื•ืชื• ืคื—ื•ืช ืกื‘ื™ืจ.
01:23
For any possible set of events, the likelihood of A occurring
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ืขื‘ื•ืจ ื›ืœ ืฆื™ืจื•ืฃ ืฉืœ ืื™ืจื•ืขื™ื, ื”ื”ืกืชื‘ืจื•ืช ืฉ ื' ื™ืงืจื”
01:27
will always be greater than the likelihood of A and B both occurring.
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ืชืžื™ื“ ืชื”ื™ื” ื’ื“ื•ืœื” ื™ื•ืชืจ ืžื”ื”ืกืชื‘ืจื•ืช ืฉื’ื ื' ื•ื’ื ื‘' ื™ืชืจื—ืฉื•.
01:33
If we took a random sample of a million people who majored in math,
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ืื ื ื™ืงื— ืžื“ื’ื ืืงืจืื™ ืฉืœ ืžืœื™ื•ืŸ ืื ืฉื™ื ืฉืœืžื“ื• ืžืชืžื˜ื™ืงื”,
01:37
the subset who are portrait artists might be relatively small.
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ื”ืงื‘ื•ืฆื” ื”ื—ืœืงื™ืช ืฉืœ ืืžื ื™ ืคื•ืจื˜ืจื˜ื™ื ื›ื ืจืื” ืชื”ื™ื” ืงื˜ื ื” ื™ื—ืกื™ืช.
01:41
But it will necessarily be bigger
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ืื‘ืœ ื”ื™ื ืชื”ื™ื” ื’ื“ื•ืœื” ื™ื•ืชืจ ื‘ื”ื›ืจื—
01:43
than the subset who are portrait artists and play poker.
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ืžื”ืงื‘ื•ืฆื” ื”ื—ืœืงื™ืช ืฉืœ ืืžื ื™ ืคื•ืจื˜ืจื˜ื™ื ืฉื”ื ื’ื ืฉื—ืงื ื™ ืคื•ืงืจ.
01:47
Anyone who belongs to the second group will also belong to the firstโ€“
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ื›ืœ ืžื™ ืฉืฉื™ื™ืš ืœืงื‘ื•ืฆื” ื”ืฉื ื™ื” ื™ื”ื™ื” ืฉื™ื™ืš ื’ื ืœืจืืฉื•ื ื” -
01:51
but not vice versa.
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ืื‘ืœ ืœื ืœื”ืคืš.
01:52
The more conditions there are, the less likely an event becomes.
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ื›ื›ืœ ืฉื™ืฉ ื™ื•ืชืจ ืชื ืื™ื, ื›ืš ื”ืกื‘ื™ืจื•ืช ื ืžื•ื›ื” ื™ื•ืชืจ ืฉืืจื•ืข ื™ืชืจื—ืฉ.
01:57
So why do statements with more conditions sometimes seem more believable?
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ืื– ืœืžื” ื”ืฆื”ืจื•ืช ืขื ื™ื•ืชืจ ืชื ืื™ื ื ืจืื•ืช ืœืคืขืžื™ื ื™ื•ืชืจ ืžืฉื›ื ืขื•ืช?
02:02
This is a phenomenon known as the conjunction fallacy.
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ื–ื• ืชื•ืคืขื” ืฉื™ื“ื•ืขื” ื›ื›ืฉืœ ื”ืฆื™ืจื•ืคื™ื•ืช.
02:05
When weโ€™re asked to make quick decisions, we tend to look for shortcuts.
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ื›ืฉืื ื—ื ื• ื ื“ืจืฉื™ื ืœืงื‘ืœ ื”ื—ืœื˜ื•ืช ืžื”ื™ืจื•ืช, ืื ื—ื ื• ื ื•ื˜ื™ื ืœื—ืคืฉ ืงื™ืฆื•ืจื™ ื“ืจืš.
02:09
In this case, we look for what seems plausible
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ื‘ืžืงืจื” ื”ื–ื”, ืื ื—ื ื• ืžื—ืคืฉื™ื ืืช ืžื” ืฉื ืจืื” ืžืชืงื‘ืœ ืขืœ ื”ื“ืขืช
02:12
rather than what is statistically most probable.
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ื‘ืžืงื•ื ืืช ืžื” ืฉืกื˜ื˜ื™ืกื˜ื™ืช ื™ื•ืชืจ ื”ื’ื™ื•ื ื™.
02:15
On its own, Lucy being an artist doesnโ€™t match the expectations
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ื‘ืคื ื™ ืขืฆืžื”, ื”ืขื•ื‘ื“ื” ืฉืœื•ืกื™ ื”ื™ื ืืžื ื™ืช ืœื ืžืชืื™ืžื” ืœืฆื™ืคื™ื•ืช
02:19
formed by the preceding information.
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ืฉื ื•ืฆืจื• ืขืœ ื™ื“ื™ ื”ืžื™ื“ืข ืฉืงื“ื.
02:22
The additional detail about her playing poker
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ื”ืžื™ื“ืข ื”ื ื•ืกืฃ ืขืœ ื–ื” ื”ื™ื ืžืฉื—ืงืช ืคื•ืงืจ
02:24
gives us a narrative that resonates with our intuitionsโ€”
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ื ื•ืชืŸ ืœื ื• ื ืจื˜ื™ื‘ ืฉืžื”ื“ื”ื“ ืขื ื”ืื™ื ื˜ื•ืื™ืฆื™ื” ืฉืœื ื• --
02:28
it makes it seem more plausible.
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ื–ื” ื’ื•ืจื ืœื–ื” ืœื”ืจืื•ืช ื™ื•ืชืจ ืืคืฉืจื™.
02:30
And we choose the option that seems more representative of the overall picture,
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ื•ืื ื—ื ื• ื‘ื•ื—ืจื™ื ืืช ื”ืืคืฉืจื•ืช ืฉื ืจืื™ืช ืฉืžื™ื™ืฆื’ืช ืืช ื”ืชืžื•ื ื” ื”ื›ืœืœื™ืช,
02:34
regardless of its actual probability.
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ื‘ืœื™ ืงืฉืจ ืœื”ืกืชื‘ืจื•ืช ื”ืืžื™ืชื™ืช ืฉืœื”.
02:37
This effect has been observed across multiple studies,
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ื”ื”ืฉืคืขื” ื”ื–ื• ื ืฆืคืชื” ืœืจื•ื—ื‘ ืžื—ืงืจื™ื ืžืจื•ื‘ื™ื,
02:41
including ones with participants who understood statistics wellโ€“
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ื›ื•ืœืœ ื›ืืœื” ืขื ืžืฉืชืชืคื™ื ืฉื”ื‘ื™ื ื• ื’ื ืกื˜ื˜ื™ืกื˜ื™ืงื” --
02:44
from students betting on sequences of dice rolls,
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ืžืกื˜ื•ื“ื ื˜ื™ื ืฉืžืชืขืจื‘ื™ื ืขืœ ืจืฆืคื™ื ืฉืœ ื–ืจื™ืงื•ืช ืงื•ื‘ื™ื”,
02:47
to foreign policy experts predicting the likelihood of a diplomatic crisis.
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ืœืžื•ืžื—ื™ ืžื“ื™ื ื™ื•ืช ื—ื•ืฅ ืฉืฆื•ืคื™ื ืืช ื”ืกื‘ื™ืจื•ืช ืฉืœ ืžืฉื‘ืจ ื“ื™ืคืœื•ืžื˜ื™.
02:53
The conjunction fallacy isnโ€™t just a problem in hypothetical situations.
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ื›ืฉืœ ื”ืฆื™ืจื•ืคื™ื•ืช ื”ื•ื ืœื ืจืง ื‘ืขื™ื” ื‘ืžืฆื‘ื™ื ื”ื™ืคื•ืชื˜ื™ื™ื.
02:57
Conspiracy theories and false news stories
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ืชืื•ืจื™ื•ืช ืงื•ื ืคื™ืจืฆื™ื” ื•ืกื™ืคื•ืจื™ ื—ื“ืฉื•ืช ืžื–ื•ื™ื™ืคื™ื
03:00
often rely on a version of the conjunction fallacy to seem credibleโ€“
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ืžืกืชืžื›ื™ื ืคืขืžื™ื ืจื‘ื•ืช ืขืœ ื’ืจืกื” ืฉืœ ืจืขื™ื•ืŸ ื›ืฉืœ ืฆื™ืจื•ืคื™ื•ืช ื›ื“ื™ ืœื”ื™ืจืื•ืช ืกื‘ื™ืจื™ื --
03:05
the more resonant details are added to an outlandish story,
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ื›ื›ืœ ืฉื™ื•ืชืจ ืคืจื˜ื™ื ืžื”ื“ื”ื“ื™ื ืžื•ืกืคื™ื ืœืกื™ืคื•ืจ ื”ืžื•ืคืจืš,
03:08
the more plausible it begins to seem.
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ื”ื•ื ื ืจืื” ื™ื•ืชืจ ืžืชืงื‘ืœ ืขืœ ื”ื“ืขืช.
03:11
But ultimately, the likelihood a story is true
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ืื‘ืœ ื‘ืกื•ืคื• ืฉืœ ื“ื‘ืจ, ื”ืกื‘ื™ืจื•ืช ืฉืœ ื”ื ื›ื•ื ื•ืช ืฉืœ ืกื™ืคื•ืจ
03:14
can never be greater than the probability that its least likely component is true.
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ืœืขื•ืœื ืœื ื™ื›ื•ืœื” ืœื”ื™ื•ืช ื’ื“ื•ืœื” ื™ื•ืชืจ ืžื”ื”ืกืชื‘ืจื•ืช ืฉื”ื—ืœืง ื”ืคื—ื•ืช ืกื‘ื™ืจ ื ื›ื•ืŸ.
ืขืœ ืืชืจ ื–ื”

ืืชืจ ื–ื” ื™ืฆื™ื’ ื‘ืคื ื™ื›ื ืกืจื˜ื•ื ื™ YouTube ื”ืžื•ืขื™ืœื™ื ืœืœื™ืžื•ื“ ืื ื’ืœื™ืช. ืชื•ื›ืœื• ืœืจืื•ืช ืฉื™ืขื•ืจื™ ืื ื’ืœื™ืช ื”ืžื•ืขื‘ืจื™ื ืขืœ ื™ื“ื™ ืžื•ืจื™ื ืžื”ืฉื•ืจื” ื”ืจืืฉื•ื ื” ืžืจื—ื‘ื™ ื”ืขื•ืœื. ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ื”ืžื•ืฆื’ื•ืช ื‘ื›ืœ ื“ืฃ ื•ื™ื“ืื• ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ ืžืฉื. ื”ื›ืชื•ื‘ื™ื•ืช ื’ื•ืœืœื•ืช ื‘ืกื ื›ืจื•ืŸ ืขื ื”ืคืขืœืช ื”ื•ื•ื™ื“ืื•. ืื ื™ืฉ ืœืš ื”ืขืจื•ืช ืื• ื‘ืงืฉื•ืช, ืื ื ืฆื•ืจ ืื™ืชื ื• ืงืฉืจ ื‘ืืžืฆืขื•ืช ื˜ื•ืคืก ื™ืฆื™ืจืช ืงืฉืจ ื–ื”.

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