Risk Perception and Communication The risks that upset people are completely different than the risks that kill people. Peter Sandman Risk Perception and Communication Wolfgang Gaissmaier, PhD Department of Psychology Social Psychology and Decision Sciences

Misperception of risk Statistical information is notoriously difficult to understand Gigerenzer, Gaissmaier, et al (2007). Psychological Science in the Public Interest People fear the wrong things: Flying ↑, Disease progression of MS↓, cardiovascular disease↓ Gaissmaier & Gigerenzer (2012). Psychological Science Heesen, Gaissmaier, et al (2013). PLoS One Oertelt-Prigione, Seeland, Kendel, Rücke, Flöel, Gaissmaier, et al (2015). BMC Medicine Slovic (1987). Science They overestimate the benefits of medical treatments Gigerenzer, Mata, & Frank (2009). JNCI Heesen, Kleiter, Nguyen, Schäffler, Kasper, Köpke, & Gaissmaier (2010). Multiple Sclerosis

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Ecological Rationality Mind Environment Gigerenzer & Gaissmaier (2011). Annual Review of Psychology

160 Gynecologists estimate: Probability of breast cancer | positive mammogram Estimates (%) Beste Schätzung Before Training Gigerenzer, Gaissmaier, Kurz-Milcke, Schwartz & Woloshin (2007). Psychological Science in the Public Interest

~10 % Mammography 10 cancer 990 no cancer 9 positive 89 1 negative 901 1000 women Natural Frequencies Conditional Probabilities p(breast cancer) = 1% p(positive|cancer) = 90% p(positive|no cancer) = 9% .01 x .90 .01 x .90 + .99 x .09 p(cancer|positive) = p(cancer|positive) = 9 9 + 89 ~10 % Mammography

160 Gynecologists estimate: Probability of breast cancer | positive mammogram Estimates (%) Best Estimate Before Training After Training Gigerenzer, Gaissmaier, Kurz-Milcke, Schwartz & Woloshin (2007). Psychological Science in the Public Interest

“I had prostate cancer, five, six years ago “I had prostate cancer, five, six years ago. My chances of surviving prostate cancer, and thank God I was cured of it, in the United States, 82 percent. My chances of surviving prostate cancer in England, only 44 percent under socialized medicine.” Rudy Giuliani New Hampshire radio advertisement, October 29, 2007

Lead time bias 9

Overdiagnosis bias 10

Wegwarth, Gaissmaier, & Gigerenzer (2010). Medical Decision Making 2 in 1,000 vs. 1.6 in 1,000 68% vs. 99% Wegwarth, Schwartz, Woloshin, Gaissmaier, & Gigerenzer (2012). Annals of Internal Medicine Wegwarth, Gaissmaier, & Gigerenzer (2010). Medical Decision Making

Facts boxes Simple tabular representation Balanced overview of benefits and harms Reducing the information to the most relevant pieces Simulatneous comparison between people with different treatments with treament vs. placebo (pre- vs. post-treatment) Are very well accepted by patients Facilitate comprehension as well as the identification of superior options Schwartz, Woloshin, & Welch (2007) Medical Decision Making Schwartz, Woloshin, & Welch (2009) Annals of Internal Medicine

Prostate Cancer Early Detection by PSA screening and digital-rectal examination. Numbers are for men aged 50 years or older, not participating vs. participating in screening for 13 years. Benefits 1,000 men without screening with How many men died from prostate cancer? 5* 4 How many men died from any cause? 200 200 Harms How many men were diagnosed and treated** for prostate cancer unnecessarily? – 30 How many men without cancer got a false alarm and a biopsy? 170 * This means that about 5 out of 1,000 men (50+ years of age) without screening died from prostate cancer within 13 years. ** With prostate removal or radiation therapy, which can lead to incontinence or impotence. Source: Schröder FH, Hugosson J, Roobol MJ, et al. (2014). The Lancet.

Graphical representations help people digest numbers are preferred reduce the influence of biases such as the ones presented earlier (framing, anecdotes, etc.) support healthy behaviors Gaissmaier et al. (2012) Health Psychology Garcia-Retamero & Cokely (2013) Current Directions in Psychological Science Trevena et al. (2013) BMC Medical Informatics and Decision Making

Prostate Cancer Early Detection by PSA screening and digital-rectal examination. Numbers are for men aged 50 years or older, not participating vs. participating in screening for 10 years. 1,000 men without screening: 1,000 men with screening: P P P P P P P P P X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Men dying from prostate cancer: Men dying from any cause: Men that were diagnosed and treated for prostate cancer unnecessarily: Men without cancer that got a false alarm and a biopsy: Remaining men 5 200 – 4 200 30 170 P X Source: Schröder FH, Hugosson J, Roobol MJ, et al. (2014). The Lancet.

Conclusions Clinical evidence is notoriously difficult to understand Statistics are an educational blind spot of many people Transparent representations foster insight But: Behavior does not really change Gaissmaier & Gigernzer (2011). Better Doctors, Better Patients, Better Decisions.

Conclusions Lack of evidence culture Ideologies often matter more than evidence How can evidence be made not only understandable, but convincing? Social heuristics: Trust in authorities (e.g., physicians) Authorities may lack understanding Conflicts of interest Defensive decision making When do social heuristics make sense? Gaissmaier & Gigernzer (2011). Better Doctors, Better Patients, Better Decisions.