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Confirmation Bias

Confirmation Bias. CCC8001 Logic and Critical Thinking. Course review. Course Instructor. Office: HSH (Ho Sin Hang) 213. Office Hours. Friday 14:00-16:00. My Email. m ichael.dracula.johnson@gmail.com. Course Website. michaeljohnsonphilosophy.com . Subject review. Critical Thinking.

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Confirmation Bias

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  1. Confirmation Bias CCC8001 Logic and Critical Thinking

  2. Course review

  3. Course Instructor

  4. Office: HSH (Ho Sin Hang) 213

  5. Office Hours Friday 14:00-16:00

  6. My Email michael.dracula.johnson@gmail.com

  7. Course Website michaeljohnsonphilosophy.com

  8. Subject review

  9. Critical Thinking Is there any evidence to support the claim? Is the evidence reliable and trustworthy? How reliable is it? Should you accept it? Does the evidence actually support the claim? Is there other evidence you should consider?

  10. Wason selection task

  11. Even vs. Odd Even numbers: 2, 4, 6, 8, 10, 12… Odd numbers: 1, 3, 5, 7, 9, 11, 13…

  12. Wason Selection Task Suppose that I present you with four cards. On each card there is a number on one side and a color (blue or red) on the other. I claim: If a card has an even number on one side then it is blueon the other side. Which of the four cards do you need to turn over to tell whether this claim is true or false?

  13. C D B A

  14. Results!

  15. Note Finding out whether a claim is true or not true is the same thing as finding out whether the claim is false or not false. • If it’s true, then it’s not false. • If it’s false, then it’s not true.

  16. Wason Selection Task Card Adoesn’t matter. First possibility: 1. The other side is blue. The claim says if it’s even, then it’s blue. It does not say that if it’s not even, then it is not blue.

  17. Example True claim: if a student makes an appointment, she can see me in my office. Does not mean false claim: if a student does not make an appointment, she cannot see me in my office.

  18. Wason Selection Task Card Adoesn’t matter. Second possibility: 2. The other side is red. The claim says even cards can’t be red. It does not say odd cards can’t be red.

  19. C D B A

  20. Wason Selection Task Card D doesn’t matter. Two possibilities: 1. The other side is even (for example, it’s “4”). The claim says if it’s even, then it’s blue. It does not say that if it’s blue, then it’s even.

  21. Example True claim: If something is a dog, then it is an animal. Does not mean false claim: if something is an animal, then it is a dog.

  22. Wason Selection Task Card D doesn’t matter. Two possibilities: 2. The other side is odd (for example, it’s “3”). The claim says if it’s even, then it’s blue. It does not say that if it’s not even, then it is not blue.

  23. C D B A

  24. Wason Selection Task Card B is important. 4 is an even number. If other side of card B is red, then the claim is false, because B is a card with an even number on one side but it is not blue on the other side. You must turn over B and make sure it is not red on the other side.

  25. C D B A

  26. Wason Selection Task Card C is also important. If the claim is true, this card must have an odd number on the other side. If it has an even number on the other side, then the claim is false. You must turn over #3 and make sure there is not an odd number on the other side.

  27. Statistical Results Around ½ of people studied say “B: 4” and “D: Blue”. About 1/3 say just “B: 4”. Only about 1/20 get the right answer: “B: 4” and “C: Red”!

  28. Analysis People look for results that would agree with the claim. Turning over B and D, you could get agreement– for example, [4, Blue] and [6, Blue]. You cannot get agreement by turning over C. But you can get disagreement and that is why the card is important!

  29. Cherry picking

  30. Cherry Picking If you see cherries in the store, you might notice that most or all of them were ripe and healthy. But you couldn’t conclude that most or all cherries are ripe and healthy. These ones have been selectively picked for good condition.

  31. Fluoride and Oral Health Fluoride is a chemical that is known to prevent tooth-decay. It is in most toothpastes and many places in the world put it in the drinking water. The US CDCP says water fluoridation is “one of 10 great public health achievements of the 20th century.”

  32. Precious Bodily Fluids Some people have decided that fluoridation of the water is bad. In the 1950’s US, some thought it was a communist conspiracy. Now some people think it’s a conspiracy of the UN or the “New World Order” or whatever.

  33. Cherry Picking “The 2011 figures show little difference [in cavity-free 5 year olds], with the rate for fluoridated areas being 59.91% and that for non-fluoridated areas being 59.18%.” (See course website for reading.)

  34. % Cavity-Free

  35. Decayed, Missing, Filled Teeth

  36. Confirmation bias

  37. Confirmation Bias People tend to look for evidence that agrees with what they already believe. This is called confirmation bias.

  38. Bacon on Confirmation Bias “The human understanding when it has once adopted an opinion… draws all things else to support and agree with it. And though there be a greater number and weight of instances to be found on the other side, yet these it either neglects and despises, or else by some distinction sets aside and rejects; in order that by this great and pernicious predetermination the authority of its former conclusions may remain inviolate.” – Sir Francis Bacon

  39. Confirmation Bias “Confirmation bias is perhaps the best known and most widely accepted notion of inferential error to come out of the literature on human reasoning.” (Evans, 1989, p. 41)

  40. Confirmation Bias “Many have written about this bias, and it appears to be sufficiently strong and pervasive that one is led to wonder whether the bias, by itself, might account for a significant fraction of the disputes, altercations, and misunderstandingsthat occur among individuals, groups, and nations.” – Nickerson 1998

  41. It’s Ordinary “Your day might start on a sour note: you wake up late, the barista screws up your coffee (even after you’ve waited forever in line), your car won’t start again. If you mentally set yourself up to say “This is a bad day,” you will look for further evidence to support that notion throughout your day, potentially ignoring evidence that it’s a day like any other or maybe even a good day overall.” -- SatyaPutumbaka

  42. Fish vs. Obama “There’s no mistaking what’s going on in the speech delivered last week. No preliminary niceties; just a rehearsal of Obama’s actions and expectations. Eight ‘I’’s right off the bat:” -- Stanley Fish

  43. “I”s “Just over two months ago I spoke with you… “ “and I laid out what needed to be done.” “From the beginning I made it clear that I would not put any more tax dollars on the line.” “I refused to let those companies become permanent wards of the state.” “I refused to kick the can down the road.” “But I also recognized the importance of a viable auto industry.” “I decided then…”

  44. Presidential Pronouns

  45. Stereotypes Stereotypes are another instance where our expectations lead us into the wrong beliefs.

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