credibility chapter 4 how believable is a claim? how credible is a source? 2 © 2009 mcgraw-hill...
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Credibility
Chapter 4Chapter 4
How believable is a claim?How credible is a source?
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Not an all-or-nothing thing!
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Statements/sources vary in credibility.
For example:For example:
“The teacher owns a duck.” “The teacher owns a dump truck.” “The teacher owns a hippopotamus.”
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Why is it harder to believe the Why is it harder to believe the teacher owns a hippopotamus? teacher owns a hippopotamus? It raises more questions.How’d she get one? Where does she keep the sucker? Say—isn’t it illegal to keep a hippo?Etc.
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In short:In short:
The idea of the teacher owning a hippo conflicts with your “background knowledge.”
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Roy
alty
-Fre
e/C
OR
BIS
“Mr. Zingg drinks a pint of sulfuric acid each night before bed.”
““Believable” is NOT entirely Believable” is NOT entirely subjective:subjective:
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Which is most Which is most UNBELIEVABLE? UNBELIEVABLE?
Teacher is under 20 years old.Teacher is under 55 year old.Teacher is under 90 years old.
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Which is LEAST unbelievable? Which is LEAST unbelievable? They’ve taught crows how to play checkers. W. arranged 9/11 so he could invade Iraq and
get its oil. Dr. Moore is related to George Washington. Bigfoot exists. We have been visited by space aliens. Some of
them are taking this class.
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Which is MOST unbelievable? Which is MOST unbelievable?
Obviously:Obviously:
The more unbelievable the claim, the stronger the argument you need to accept it.
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For example:For example:
“Dean Stooler can run a mile in less than four minutes.”
“Dean Stooler can run a mile in less than seven minutes.”
More is required to establish the first statement.
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Watch out for things you accept Watch out for things you accept just because you’ve heard them just because you’ve heard them
so often:so often:A critical thinker will want EVIDENCE
before accepting “what everyone knows.”
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Old wives’ tales?Old wives’ tales?
Daddy long legs are the world’s most poisonous spider.
Eating carrots makes you see better. Aspirin with Coca-Cola will make you drunk. Pop Rocks followed by Pepsi can make your
stomach explode. Going outside with wet hair will give you a cold.
(more…)
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Old wives’ tales?Old wives’ tales?
Reading in dim light will hurt your eyes. Too much TV will hurt your eyes. Chocolate causes pimples. Coffee stunts your growth. Crossing your eyes can make you cross-eyed. Cracking your knuckles causes arthritis.
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Credibility of SourcesCredibility of Sources
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Two kinds of doubt:Two kinds of doubt:
1. Doubts about a source’s knowledge
2. Doubts about a source’s truthfulness, objectivity, reliability
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““Smitty knows a lot, but you Smitty knows a lot, but you can’t trust a word he says.”can’t trust a word he says.”
“Smitty never lies, but he “Smitty never lies, but he doesn’t know a thing.”doesn’t know a thing.”
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Either way, Smitty isn’t the best source.
Q: Can you tell if a person (not someone you know) is lying to you?
Are there any tell-tale clues?
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Excessive sweating? Shifty eye movement/avoiding eye contact? Staring up to the left/other micro-expressions? Wimpy handshake? Changing the subject? Appearing lacking in self-confidence? Nervous laughter?
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If any of these were at all If any of these were at all reliable, we wouldn’t need reliable, we wouldn’t need
courts, ID checks, lie courts, ID checks, lie detectors, blah blah blah…detectors, blah blah blah…
Why would teachers take precautions against cheating, if they could just
look at a kid and tell?
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Need four volunteers!
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A more scientific experiment:Need just two volunteers…
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Here are your “voting” options.Here are your “voting” options.
T/T: Both telling truth
L/L: Both lying
T/L: First person truthful; second is lying
L/T: First person lying; second is truthful
Even a truthful source can:Even a truthful source can:
Make MISTAKESBe BIASEDLACK EXPERTISE
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How to judge a person’s expertise?
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Self-confidence/nervousness?
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Clothes?
Posture?
Accent?Gender?
Nationality?
Those all seem pretty unreliable.
Anyone can LOOK like an authority…
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Height?
http://news.bbc.co.uk/2/hi/health/3200296.stm
How would YOU make How would YOU make someone look like a scientist?someone look like a scientist?
Use a stereotype! White lab coat or poor-fitting suit Pocket protector Glasses; thick Gray hair German/British accent, etc.
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Conclusion:Conclusion:
It’s difficult to measure a It’s difficult to measure a person’s expertise by looking at person’s expertise by looking at
him or her.him or her.
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BEST indicators of a source’s BEST indicators of a source’s knowledge are these:knowledge are these:
EducationExperienceReputationPositionAchievements
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Does being an expert in one field Does being an expert in one field make you an expert in another field?make you an expert in another field? Not if the two fields aren’t related. An expert in economics doesn’t automatically
qualify as expert in, say, political science. An expert in oceanography shouldn’t be
assumed to be an expert in genetics. Your business prof can’t be assumed to have
expert knowledge of history.
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A common mistake:A common mistake:
To attach EXTRA authority to what someone says JUST because he/she:Is your parentIs your friendIs your teacher (Being a TEACHER carries extra weight in the person’s field, but the fact he/she is YOUR teacher doesn’t add anything.)
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Other sources:Other sources:
Newspapers; other print media Electronic media; TV, radio The Internet is actually a source of
sources, not a source in itself. University publications Government publications Professional journals
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An example of an unreliable An example of an unreliable news source…?news source…?
The weekly rag available in the checkout line.
REDNECK ALIENS TAKE OVER REDNECK ALIENS TAKE OVER TRAILER PARK!TRAILER PARK!
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A much better source:A much better source:
The website of the Sacremento Bee
http://www.sacbee.com/
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Even better (because more Even better (because more complete):complete):
The New York Times newspaper
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One final idea…One final idea…
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Sometimes you get an Sometimes you get an unbelievable claim coming unbelievable claim coming
from a credible source.from a credible source.
Like, say, from a friend or a relative.
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Like, I had an aunt who was Like, I had an aunt who was convinced she saw a ghost. convinced she saw a ghost.
Good old Aunt Rose…she had no reason to lie, and she was as
honest as the day is long.
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This brings us to Hume’s This brings us to Hume’s principle. principle.
Hume?
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David HumeDavid Hume
David Hume (1711-1776), a nice chap. Liked to play whist. Here’s what he said…
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Hume’s principle:Hume’s principle:
“No testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous than the fact it endeavors to establish.”
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“When anyone tells me he saw a dead man restored to life, I consider whether it be more probable that this person should either deceive or be deceived, or that the fact he relates should really have happened. I weigh the one miracle against the other; and always reject the greater miracle. If the falsehood of his testimony would be more miraculous than the event which he relates, then, and not till then, can he pretend to command my belief or opinion.”
“When anyone tells me he saw a dead man restored to life, I consider whether it be more probable that this person should either deceive or be deceived, or that the fact he relates should really have happened. I weigh the one miracle against the other; and always reject the greater miracle. If the falsehood of his testimony would be more miraculous than the event which he relates, then, and not till then, can he pretend to command my belief or opinion.”
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