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Credibility Chapter 4 How believable is a claim? How credible is a source? 2 © 2009 McGraw-Hill Higher Education. All rights reserved.

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Presentation on theme: "Credibility Chapter 4 How believable is a claim? How credible is a source? 2 © 2009 McGraw-Hill Higher Education. All rights reserved."— Presentation transcript:

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2 Credibility Chapter 4

3 How believable is a claim? How credible is a source? 2 © 2009 McGraw-Hill Higher Education. All rights reserved.

4 Not an all-or-nothing thing! 3 © 2009 McGraw-Hill Higher Education. All rights reserved. Statements/sources vary in credibility.

5 For example: “The teacher owns a duck.” “The teacher owns a dump truck.” “The teacher owns a hippopotamus.” 4 © 2009 McGraw-Hill Higher Education. All rights reserved.

6 Why is it harder to believe the 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. 5 © 2009 McGraw-Hill Higher Education. All rights reserved.

7 In short: The idea of the teacher owning a hippo conflicts with your “background knowledge.” 6 © 2009 McGraw-Hill Higher Education. All rights reserved.

8 7 Royalty-Free/CORBIS

9 “Mr. Zingg drinks a pint of sulfuric acid each night before bed.” “Believable” is NOT entirely subjective: 8 © 2009 McGraw-Hill Higher Education. All rights reserved.

10 Which is most UNBELIEVABLE? Teacher is under 20 years old. Teacher is under 55 year old. Teacher is under 90 years old. 9 © 2009 McGraw-Hill Higher Education. All rights reserved.

11 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. 10 © 2009 McGraw-Hill Higher Education. All rights reserved. Which is MOST unbelievable?

12 Obviously: The more unbelievable the claim, the stronger the argument you need to accept it. 11 © 2009 McGraw-Hill Higher Education. All rights reserved.

13 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. 12 © 2009 McGraw-Hill Higher Education. All rights reserved.

14 Watch out for things you accept just because you’ve heard them so often: A critical thinker will want EVIDENCE before accepting “what everyone knows.” 13 © 2009 McGraw-Hill Higher Education. All rights reserved.

15 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…) 14 © 2009 McGraw-Hill Higher Education. All rights reserved.

16 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. 15 © 2009 McGraw-Hill Higher Education. All rights reserved.

17 Credibility of Sources 16 © 2009 McGraw-Hill Higher Education. All rights reserved.

18 Two kinds of doubt: 1. Doubts about a source’s knowledge 2. Doubts about a source’s truthfulness, objectivity, reliability 17 © 2009 McGraw-Hill Higher Education. All rights reserved.

19 “Smitty knows a lot, but you can’t trust a word he says.” “Smitty never lies, but he doesn’t know a thing.” 18 © 2009 McGraw-Hill Higher Education. All rights reserved. Either way, Smitty isn’t the best source.

20 Q: Can you tell if a person (not someone you know) is lying to you? Are there any tell-tale clues? 19 © 2009 McGraw-Hill Higher Education. All rights reserved.

21 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? 20 © 2009 McGraw-Hill Higher Education. All rights reserved.

22 If any of these were at all reliable, we wouldn’t need courts, ID checks, lie detectors, blah blah blah… Why would teachers take precautions against cheating, if they could just look at a kid and tell? 21 © 2009 McGraw-Hill Higher Education. All rights reserved.

23 Need four volunteers! 22 © 2009 McGraw-Hill Higher Education. All rights reserved.

24 A more scientific experiment: Need just two volunteers… 23 © 2009 McGraw-Hill Higher Education. All rights reserved.

25 24 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

26 Even a truthful source can: Make MISTAKES Be BIASED LACK EXPERTISE 25 © 2009 McGraw-Hill Higher Education. All rights reserved.

27 How to judge a person’s expertise? 26 © 2009 McGraw-Hill Higher Education. All rights reserved.

28 Self-confidence/nervousness? 27 © 2009 McGraw-Hill Higher Education. All rights reserved. Clothes? Posture? Accent? Gender? Nationality ?

29 Those all seem pretty unreliable. Anyone can LOOK like an authority… 28 © 2009 McGraw-Hill Higher Education. All rights reserved.

30 29 © 2009 McGraw-Hill Higher Education. All rights reserved. Height? stm

31 How would YOU make 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. 30 © 2009 McGraw-Hill Higher Education. All rights reserved.

32 Conclusion: It’s difficult to measure a person’s expertise by looking at him or her. 31 © 2009 McGraw-Hill Higher Education. All rights reserved.

33 BEST indicators of a source’s knowledge are these: Education Experience Reputation Position Achievements 32 © 2009 McGraw-Hill Higher Education. All rights reserved.

34 Does being an expert in one 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. 33 © 2009 McGraw-Hill Higher Education. All rights reserved.

35 A common mistake: To attach EXTRA authority to what someone says JUST because he/she: Is your parent Is your friend Is 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.) 34 © 2009 McGraw-Hill Higher Education. All rights reserved.

36 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 35 © 2009 McGraw-Hill Higher Education. All rights reserved.

37 An example of an unreliable news source…? The weekly rag available in the checkout line. REDNECK ALIENS TAKE OVER TRAILER PARK! 36 © 2009 McGraw-Hill Higher Education. All rights reserved.

38 A much better source: The website of the Sacremento Bee 37 © 2009 McGraw-Hill Higher Education. All rights reserved.

39 Even better (because more complete): The New York Times newspaper 38 © 2009 McGraw-Hill Higher Education. All rights reserved.

40 One final idea… 39 © 2009 McGraw-Hill Higher Education. All rights reserved.

41 Sometimes you get an unbelievable claim coming from a credible source. Like, say, from a friend or a relative. 40 © 2009 McGraw-Hill Higher Education. All rights reserved.

42 Like, I had an aunt who was 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. 41 © 2009 McGraw-Hill Higher Education. All rights reserved.

43 This brings us to Hume’s principle. Hume? 42 © 2009 McGraw-Hill Higher Education. All rights reserved.

44 David Hume David Hume ( ), a nice chap. Liked to play whist. Here’s what he said… 43 © Library of Congress

45 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.” 44 © 2009 McGraw-Hill Higher Education. All rights reserved.

46 “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.” 45 © 2009 McGraw-Hill Higher Education. All rights reserved.


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