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Delusion delusion slideshare

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Public lecture, Mary Immaculate College, University of Limerick, 9 April 2013

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Delusion delusion slideshare

  1. 1. The ‘Delusion’ Delusion:The persistence of counter-evidentiaryreasoningBrian HughesNational University of Ireland, Galway
  2. 2. Number of tickets sold for the last MillionaireRaffle = 180,000Once-off chance of success = 1 in 180,000But, four Millionaire Raffles each year, givingyou four chances of winningCorrected chance of being attacked by a bear = 1 in270,000Corrected number of bear attacks in Ireland perannum = 17Therefore…Chance of being attacked by a bear = 1 in 1,080,000Number of bear attacks in Ireland = 4Pr (millionaire) = 6 x Pr (bear attack)HT locum-motion on boards.ie
  3. 3. Extinct in Ireland
  4. 4. http://www.fark.com/comments/7535504/Not-to-alarm-anyone-but-Google-may-have-run-over-a-donkey-in-Botswana
  5. 5. http://www.neowin.net/news/google-maps-car-hits-a-deer-records-it-all
  6. 6. Mail on Sunday, 10 February 2013
  7. 7. Private Eye, 22 February 2013
  8. 8. http://www.gallup.com/poll/19558/Paranormal-Beliefs-Come-SuperNaturally-Some.aspx
  9. 9. http://www.gallup.com/poll/19558/Paranormal-Beliefs-Come-SuperNaturally-Some.aspx
  10. 10. http://goo.gl/SReC0
  11. 11. “Delusions bad”?
  12. 12. Linda is 31 years old, single, outspoken, and very bright. As astudent, she was deeply concerned with issues of discriminationand social justice.Which of the following is most likely:(a) Linda is a bank teller(b) Linda is a bank teller and is active in the feminist movement
  13. 13. Linda is 31 years old, single, outspoken, and very bright. As astudent, she was deeply concerned with issues of discriminationand social justice.Which of the following is most likely:(a) Linda is a bank teller(b) Linda is a bank teller and is active in the feminist movement
  14. 14. Conjunction fallacyIF Pr (Linda is a bank teller) = 0.10AND Pr (Linda is a feminist) = 0.95…THEN Pr (Linda is a bank teller anda feminist)= 0.10 × 0.95= or 0.095i.e., lower than Pr (Linda is a bank teller)Based on http://paradigmsanddemographics.blogspot.com/2011/09/logical-fallacy-of-week-conjunction.html
  15. 15. A 55-year-old woman had pulmonary embolism documentedangiographically 10 days after cholecystectomy.Rate the likelihood of the following subsequent after-effects:(a) The woman experienced pleuritic chest pain(b) The woman experienced dyspnea and hemiparesis(c) The woman experienced hemiparesis(d) The woman experienced hemoptysis(e) etc.
  16. 16. 12345Dyspnea ANDHemiparesisHemiparesisMoreprobableLessprobable37 medical postgrads at Harvard Universityplus 66 internists at New England Medical Center32 physicians at Stanford UniversityTversky & Kahneman (1983)
  17. 17. Tossing one coin, what is thechance of it landing on “Heads”?A:0.50(or, in other words, a fifty-fifty chance)Throwing one dice, what is thechance of it landing on “5”?A: 0.17(or, in other words, a one-in-six chance)Difficulties with probabilistic reasoning
  18. 18. Tossing two coins, what is thechance of getting two “Heads”?A: 0.25(or, in other words, a 1-in-4 chance)Throwing two dice, what is thechance of getting two “5”s?A: 0.028(or, in other words, a 1-in-36 chance)Difficulties with probabilistic reasoning
  19. 19. Difficulties with probabilistic reasoningIf a test to detect a disease whose prevalence is 1/1000 hasa false positive rate of 5%, what is the chance that a personfound to have a positive result actually has the disease,assuming you know nothing about the person’s symptomsor signs?Cited by Pinker (1997)•Among Staff and Students of Harvard Medical School (n = 60):Most popular answer= 0.95 (i.e., a 19 out of 20 chance)Average of all answers= 0.56 (c., a fifty-fifty chance)
  20. 20. 999/1000 x .05Difficulties with probabilistic reasoningCited by Pinker (1997)[Base-rate] x [Test sensitivity] / [Rate of positive results][1/1000]Prevalence ofdisease per 1000[1/1]Proportion of sick whotest positiveNumber of positiveresults per 10001/1000 + ([ )]“False positives”i.e., well persons whotest ‘positive’Actual sickpersons testing‘positive’If a test to detect a disease whose prevalence is 1/1000 hasa false positive rate of 5%, what is the chance that a personfound to have a positive result actually has the disease,assuming you know nothing about the person’s symptomsor signs?
  21. 21. )]+ (0.001 0.049950.001 1.0Difficulties with probabilistic reasoningCited by Pinker (1997)[Base-rate] x [Test sensitivity] / [Rate of positive results]= 0.019627[x /== 0.001 / 0.05095≈ 0.02If a test to detect a disease whose prevalence is 1/1000 hasa false positive rate of 5%, what is the chance that a personfound to have a positive result actually has the disease,assuming you know nothing about the person’s symptomsor signs?
  22. 22. •Among Staff and Students of Harvard Medical School (n = 60):Most popular answer= 0.95 (i.e., a 19 out of 20 chance)Average of all answers= 0.56 (c., a fifty-fifty chance)Difficulties with probabilistic reasoningCited by Pinker (1997)≈ 0.02 (or, in other words, a 1-in-50 chance)If a test to detect a disease whose prevalence is 1/1000 hasa false positive rate of 5%, what is the chance that a personfound to have a positive result actually has the disease,assuming you know nothing about the person’s symptomsor signs?
  23. 23. Difficulties with probabilistic reasoningGøtzsche PC, Nielsen M. Screening for breast cancer with mammography. Cochrane Database ofSystematic Reviews 2006, Issue 4. Art. No.: CD001877. DOI: 10.1002/14651858.CD001877.pub2…For every 2000 women invited for screeningthroughout 10 years, one will have her lifeprolonged. In addition, 10 healthy women, whowould not have been diagnosed if there had notbeen screening, will be [erroneously] diagnosedand treated unnecessarily…
  24. 24. http://goo.gl/0D4JC
  25. 25. Coincidences•Lucia de Berk (Wikipedia)–Dutch nurse sentenced to lifeimprisonment in 2003–Found guilty of four murders andthree attempted murders, largelyon statistical evidence–“one in 342 million against”–Problems:• Multiplied p-values• Did not compare against base-rate–Case re-opened in 2008–Exonerated in April 2010
  26. 26. “Delusions bad”?
  27. 27. “Delusions good”?
  28. 28. www.gallup.com/poll/27847/Majority-Republicans-Doubt-Theory-Evolution.aspx
  29. 29. Tendency toward non-empiricalbeliefs may be physiologically in-built
  30. 30. Non-empirical beliefs may promoteinclusive fitnessSosis, R. (2000). Religion and intragroup cooperation: Preliminary results of a comparative analysis of Utopian communities.Cross-Cultural Research, 34, 70–87.
  31. 31. Non-empirical thinking may serve asa “costly signal” of individual fitnessSosis, R., & Bressler, E. (2003). Cooperation and commune longevity: A test of the costly signaling theory of religion. Cross-Cultural Research, 37, 211–239.
  32. 32. Faulty beliefs may boost one’s self-esteemAboveaverage70%Average28%Belowaverage2%Self-rated "Leadership ability"Data from 1,000,000 studentsCited by Gilovich (1991)
  33. 33. Faulty beliefs may boost one’s self-esteemData from 1,000,000 studentsCited by Gilovich (1991)Self-rated "Ability to get along with others"Aboveaverage100%
  34. 34. Faulty beliefs may boost one’s self-esteemData from 1,000,000 studentsCited by Gilovich (1991)“Top 1%”25%“Also in topquarter”35%
  35. 35. Faulty beliefs may boost one’s self-esteemAboveaverage94%Belowaverage6%Competence at one’s jobData from university lecturersCited by Gilovich (1991)
  36. 36. Faulty beliefs may boost one’s self-esteemEveryoneAll-round greatness“Me!”
  37. 37. Common illusionsUnrealistically positive self-regardIllusions of controlUnrealistic optimismBenefitsHappiness or contentmentAbility to care for othersCapacity for creativity/productivityFaulty beliefs may be the brain’sdefault state
  38. 38. Depression, confidence, and accuracySzu-Ting Fu, T., Koutstaal, W., Poon, L., & Cleare, A. J. (2012). Confidence judgment in depression anddysphoria: The depressive realism vs. negativity hypothesis. Journal of Behavior Therapy andExperimental Psychiatry, 43, 699-704.
  39. 39. Szu-Ting Fu, T., Koutstaal, W., Poon, L., & Cleare, A. J. (2012). Confidence judgment in depression anddysphoria: The depressive realism vs. negativity hypothesis. Journal of Behavior Therapy andExperimental Psychiatry, 43, 699-704.00.020.040.060.080.10.12Healthy Depressed Chronic FatigueSyndromeOver-confidence (i.e., estimate – reality)during task
  40. 40. Szu-Ting Fu, T., Koutstaal, W., Poon, L., & Cleare, A. J. (2012). Confidence judgment in depression anddysphoria: The depressive realism vs. negativity hypothesis. Journal of Behavior Therapy andExperimental Psychiatry, 43, 699-704.
  41. 41. Impact on recall of depressive statesBen-Zeev, D., & Young, M. A. (2010). Accuracy of hospitalized depressed patients’ and healthy controls’retrospective symptom reports. Journal of Nervous and Mental Disease, 198, 280-285.Practical Emotional
  42. 42. Too much of a bad thingSoderstrom, N. C., Davalos, D. B., & Vázquez, S. M. (2011). Metacognition and depressive realism:Evidence for the level-of-depression account. Cognitive Neuropsychiatry, 16, 461-472.
  43. 43. Too much of a bad thingSoderstrom, N. C., Davalos, D. B., & Vázquez, S. M. (2011). Metacognition and depressive realism:Evidence for the level-of-depression account. Cognitive Neuropsychiatry, 16, 461-472.
  44. 44. http://www.practiceofmadness.com/2010/03/psychiatric-drugs-a-history-in-ads/
  45. 45. http://www.practiceofmadness.com/2010/03/psychiatric-drugs-a-history-in-ads/
  46. 46. http://www.pharmacytechs.net/blog/old-school-medicine-ads
  47. 47. http://www.practiceofmadness.com/2010/03/psychiatric-drugs-a-history-in-ads/
  48. 48. http://www.practiceofmadness.com/2010/03/psychiatric-drugs-a-history-in-ads/
  49. 49. The “Third-Person Effect”Davison, W. P. (1983). The Third-Person Effect in communication. Public Opinion Quarterly, 47, 1-15.Self influenced byadvertisingOthers influencedby advertisingQuite a lot 32% 68%Some 24% 28%Not very much 20% 4%Not at all 16% 0%N/A 8% 0%
  50. 50. Impact of depression on Third Person Effect,for anti-depressant advertisementsTaylor, L. D., Bell, R. A., & Kravitz, R. L. (2011). Third-person effects and direct-to-consumeradvertisements for antidepressants. Depression and Anxiety, 28, 160-165.
  51. 51. Human irrationalityis often ‘explainedaway’ in a self-serving fashionThis informs the waywe try to deal withdelusional beliefs inthe public sphereDelusions may infact serve protectivefunctions and so bedifficult to shift……but just becausedelusions are‘natural’ does notmake them ‘good’!brian.hughes@nuigalway.iehttp://thesciencebit.net
  52. 52. Human irrationalityis often ‘explainedaway’ in a self-serving fashionThis informs the waywe try to deal withdelusional beliefs inthe public sphereDelusions may infact serve protectivefunctions and so bedifficult to shift……but just becausedelusions are‘natural’ does notmake them ‘good’!brian.hughes@nuigalway.iehttp://thesciencebit.net

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