This post looks at the medical/health component of decision making as addressed in Gerd Gigerenzer’s new book, Risk Saavy, How to Make Good Decisions. First, Gigerenzer has contributed greatly to improving health decision making. This blog includes three consecutive posts on the Statistics of Health Decision Making based on Gigerenzer’s work.
He points out both the weaknesses of screening tests and our understanding of the results. We have to overcome our tendency to see linear relationships when they are nonlinear. Doctors are no different. The classic problem is an imperfect screening test for a relatively rare disease. You cannot think in fractions or percentages. You must think in absolute frequencies. Breast cancer screening is one example. Generally, it can catch about 90% of breast cancers and only about 9% test positive who do not have breast cancer. So if you have a positive test, that means chances are you have breast cancer. No! You cannot let your intuition get involved especially when the disease is more rare than the test’s mistakes. If we assume that 10 out of 1000 women have breast cancer, then 90% or 9 will be detected, but about 90 of the 1000 women will test positive who do not have disease. Thus only 9 of the 99 who test positive actually have breast cancer. I know this, but give me a new disease or a slightly different scenario and let a month pass, I will still be tempted to shortcut the absolute frequencies and get it wrong.
Gerd Gigerenzer has a 2014 book out entitled: Risk Saavy,How to Make Good Decisions, that is a refinement of his past books for the popular press. It is a little too facile, but it is worthwhile. Gigerenzer has taught me much, and he will likely continue. He is included in too many posts to provide the links here (you can search for them). My discussion of the book will be divided into two posts. This one will be a general look, while the next post will concentrate on Gigerenzer’s take on medical decision making.
As in many books like this, the notes provide insight. Gigerenzer points out his disagreements with Kahneman with respect to heuristics all being part of the unconscious system. As he notes heuristics, for instance the gaze heuristic, can be used consciously or unconsciously. This has been a major issue in my mind with Kahneman’s System 1 and System 2. Kahneman throws heuristics exclusively into the unconscious system. I also side with Gigerenzer over Kahneman, Ariely, and Thaler that the unconscious system is associated with bias. As Gigerenzer states: “A system that makes no errors is not intelligent.” He interestingly points out the use of the gaze heuristic by Sully Sullenberger to decide to not return to LaGuardia, but instead to land in the Hudson River.
This post is based on the paper: “The Affect Gap in Risky Choice: Affect-Rich Outcomes Attenuate Attention to Probability Information,” authored by Thorsten Pachur, Ralph Hertwig, and Roland Wolkewitz that appeared in Decision, 2013, Volume 1, No. 1, p 64-78. This is a continuation of the affect/ emotion theme. It is more of a valence based idea than Lerner’s Appraisal Tendency Framework. This is more thinking about emotion than actually experiencing it although the two can come together.
Often risky decisions involve outcomes that can create considerable emotional reactions. Should we travel by plane and tolerate a minimal risk of a fatal terrorist attack or take the car and run the risk of traffic jams and car accidents? How do people make such decisions? Decisions under risk typically obey the principle of the maximization of expectation.
The expectation expresses the average of an option’s outcomes, each weighted by its
probability. This, of course, underlies expected utility theory and cumulative prospect theory and these models do a good job in accounting for choices among relatively affect-poor
This post is based on a paper by Rebecca Ferrer, William Klein, Jennifer Lerner, Valerie Reyna, and Dacher Keltner: “Emotions and Health Decison-Making, Extending the Appraisal Tendency Framework to Improve Health and Healthcare,” in Behavioral Economics and Public Health, 2014. I note that Valerie Reyna is one of the authors of fuzzy trace theory (see post Fuzzy Trace Theory-Meaning, Memory, Development and subsequent posts.) which I find interesting.
The authors use the appraisal tendency framework (ATF) to predict how emotions may interact with situational factors to improve or degrade health-related decisions. The paper examines four categories of judgments and thought processes as related to health decisions: risk perception, valuation and reward-seeking, interpersonal attribution, and depth of information processing. They illustrate ways in which a better understanding of emotion can improve judgments and choices regarding health.
The ATF assumes that specific emotions give rise to corresponding cognitive and motivational processes that are related to the target of the emotion (i.e., the situation, person, or other stimulus that elicited the emotion). In contrast to theories that predict how broad mood states (positive or negative) may influence judgment and decision making, the ATF offers specific predictions for how discrete emotions will influence judgment and decision making (See Tables 1 and 2).
This post examines a couple of applications of Signal Detection Theory. Both are technically beyond me, but the similarities in the applications seem instructive. In both articles, SDT is used to evaluate questionnaire type screening tools. This is not a big surprise since it is where most of us first saw applications of statistical hypothesis testing and those false positives and false negatives. One paper looks at BRCA genetic risk screening and the other depression screening. In both cases, the screening instruments do not propose to be gold standards, but only introductory screening. It might be the type of screening that internal medicine doctors might do. In both cases, there is the idea that pure probability based instruments are ineffective, due to the biases that most people carry with them. One paper utilizes a fast and frugal decision tree(FFT) and the other three risk categories to provide the gist as in fuzzy trace theory(FTT). This gives us promotion of two similar acronyms: FFT and FTT.
Dan Kahan has an article in the October 2013, issue of Science, “A Risky Science Communication
Environment for Vaccines,” with a specific example of the HPV vaccine issues. Kahan has written a good article and one that may have not pleased several people. It fits together with my post Web 2.0 for Vaccination Decisions. Kahan makes the case for having scientifically based scientific risk communication strategies which is something that Betsch and Reyna et al try to do in “Opportunities and challenges of Web 2.0 for vaccination decisions.” Kahan may make a bigger case for just not being stupid and ignoring everything we already know about risk communication. He says quite well although indirectly that vaccination is really not a cultural cognition issue–yet, but we could make it one if we are not careful.
In his latest book, The World Until Yesterday, Jared Diamond looks at how several societies that have avoided technological advancements over long periods of recent time can teach us something. He calls them traditional societies. He indicates that you can look at these traditional societies as separate experiments of how a society develops and maybe by picking and choosing, you can find ways to enhance today’s first world societies. Dealing with risk and making decisions are part of that.
Ben Bernanke, chairman of the Federal Reserve, gave a news conference last week. Since then mortgage rates have jumped about half a percent along with 10 year treasury notes. The stock market is also down. Interestingly, Bernanke appeared to be trying to calm things down and did his best to provide the detail that analysts, investors, and the press wanted without really changing anything that he had said before. My first reaction is that when the Fed is asked for more clarity, they are really being asked for a secret signal for when the rats should get off the ship. So Bernanke, like the public health officials trying to communicate about vaccines, is a risk communicator.
On June 26, 2013, David Wessel wrote his Wall Street Journal column “Capital” about Bernanke’s efforts, and provided some interesting comments. Wessel indicated that maybe Bernanke did not “appreciate how hard it is to predict how markets will react to lengthy explanations.” Or perhaps markets were just ready to change course and “Mr Bernanke provided the moment.” Fuzzy trace theory seems to have a place here. Over the last few years, Bernanke’s gist has been that the fed among all possible actors would do whatever it could to help the economy and reduce unemployment. His lengthy explanation last week indicated that he had been thinking a lot about being ready to change this. Maybe that changed the gist from full speed ahead to easing off. The slightly more complicated message changed the gist.
Goldman Sachs boss Lloyd Blankfein whose economists interpreted the news conference as “a hawkish surprise” was quoted by Wessel as saying before the news conference: “Even if the Fed wants to change its rate slowly, at the first indication of change, the markets will change it quickly. If you want to handle that in the best way, you create a little bit more uncertainty in the market in the less aggressive, less jarring way.” We can hope that Bernanke is so confident about the economy that he thought that it was time to muddy up the gist and shake some of the “irrational exuberance” out of the markets. If the economy sputters, I hope that Bernanke can go back to a memorable positive gist to renew confidence about the Fed’s actions.
Blankfein makes an interesting point when he notes that at the first indication of change, the markets will change quickly. This is almost like a phase change in physics where ice melts. You do not have to change the temperature much to have a completely different situation on your hands. Public health vaccination communicators are concerned that this could happen with viral messages on the internet that undermine the advances made by vaccination programs.
This post looks at a paper that was put together at a conference on risk perception and risk communication regarding vaccination decisions in the age of social media. The paper: “Opportunities and challenges of Web 2.0 for vaccination decisions”, was published in the Journal Vaccine 30(2012)3727-3733. Two of the authors are Cornelia Betsch and Valerie Reyna. I think both of them are insightful.