Friday, October 17, 2014

Assessing Ebola Risk: Unbounded Irrationality?

In the mid-1950's cognitive psychologist and economist Herbert Simon coined the term "Bounded Rationality" to refer to the suboptimal way people sometimes reach decisions and assess risk.  Simon's analysis and complementary work by Paul Slovic, Amos Tversky, Noble Prize-winner Daniel Kahnemann and others has led to decades of careful research that clearly establishes the limits of our rational evaluation of information in making judgments about a wide variety of topics, including investment decisions, environmental threats, and health risks.

For example, our limited cognitive resources often lead us to rely on mental shortcuts and intuitive processes rather than careful, rational analysis, and this can lead to errors in judgements and decisions. One such shortcut that often comes into play is judging risk based upon the ease with which relevant instances comes to mind, the Availability Heuristic -- a potential event seems more likely if we can easily bring to mind examples of its attributes. Availability of information in memory can be influenced by many things: its recency of having been accessed, its vividness when initially encountered, its emotional intensity, or the frequency with which a person has been exposed to it.

Another instance of bounded rationality that seems relevant here is the context in which we think about a given potential event.  Research by Kahnemann and Tversky showed the dramatic effect that context can have on our judgments, which they called "Framing Effects" (this work is nicely summarized in Kahnemann's 2002 Nobel Prize acceptance speech).  In several studies they presented participants with simple thought exercises in which they were asked to choose which of two alternative courses of action they would prefer in hypothetical cases concerning, for example, an outbreak of an unusual Asian disease (substitute "African" for Asian and the parallel to our current situation with Ebola is particularly poignant)  One group of participants were given the following scenario:
Imagine that the United States is preparing for the outbreak of an unusual Asian disease, which is expected to kill 600 people. Two alternative programs to combat the disease have been proposed. Assume that the exact scientific estimates of the consequences of the programs are as follows:

If Program A is adopted, 200 people will be saved

If Program B is adopted, there is a one-third probability that 600 people will be saved and a two-thirds probability that no people will be saved
Which of the two programs would you favor? 
A substantial majority of respondents favor program A, choosing the certainty of saving 200 of the 600 people over the more uncertain possibility that all of them might be saved if Program B is adopted.

Another group of participants received the same background scenario (i.e., 600 are likely to die) but two different choices:
If Program A is adopted, 400 people will die
If Program B is adopted, there is a one-third probability that nobody will die and a two-thirds probability that 600 people will die
Note that in both cases the outcomes associated with the two choices are the same. If Choice A is adopted 200 people will be saved and 400 will die, but the outcomes are framed differently -- in the first case the certainty of 200 being saved is emphasized whereas in the second it is the certainty of 400 dying.  When presented with the second pair of choices, a clear majority of respondents favor program B, even though its adoption has a less certain outcome. As Kahnemann notes, "the certainty of saving people is disproportionately attractive, and the certainty of deaths is disproportionately aversive."

Paul Slovic's work also seems highly relevant to understanding the American public's reaction to Ebola.  His approach has focused on the factors that lead to people's emotional reactions to potential threats and that alter their tolerance for risk. Sara Gorman succinctly summarizes the results of Slovic's research as follows: "People tend to be intolerant of risks that they perceive as being uncontrollable, having catastrophic potential, having fatal consequences, or bearing an inequitable distribution of risks and benefits...The higher a hazard scores on these factors, the higher its perceived risk and the more people want to see the risk reduced, leading to calls for stricter regulation."  Note that it is the "dread factor" that leads to assessments of risk, and this may not be closely related to the objective probability of a hazard.

Is the current furor in the U.S. concerning the Ebola outbreak in west Africa a textbook example of bounded rationality?
Health worker donning protective gear
From media coverage of the outbreak, you might expect that this would be the case, with Americans overestimating the risk and endorsing objectively ineffective extreme measures of protection to reduce the perceived threat. Media reporting of the outbreak has been vivid, frequent, and sensational, emphasizing the
highly infectious nature of Ebola, its deadliness, the horrible nature of the symptoms, and the fact that there is no known cure. This is this a news topic that is sure to grab people's attention and news organizations have been quick to exploit this, as they typically do with negative events. Far less coverage has emphasized the low probability of contagion in the U.S. because direct contact is required to pass the disease, and that the virus is short-lived outside of the host -- Ebola is highly infectious (a small amount of the live virus leads to illness) but not very contagious (easily passed from person to person).

CDC image of the virus
...Ebola is a natural for cable news, where fear means viewers and it’s easy to tap into narratives we’ve seen play out in a dozen movies and television shows....There is sensationalist coverage everywhere, in which networks with time to fill spend hours on baseless speculation and nightmare scenarios...if you find yourself with symptoms including anxiety, sweating, and a clutching in your chest, you’ve probably been watching too much television." Print media is also vivid and dire in its coverage, with headlines like:  "Why Ebola is so dangerous"; "How Ebola sped out of control;" "Ebola outbreak: Why Obama is allowing Ebolaphobia to spread;" "New Ebola Cases May Soon Reach 10,000 a Week, Officials Predict;" "An epidemic of fear and anxiety hits Americans amid Ebola outbreak."

Surprisingly, despite the nature of this coverage, until recently Americans were relatively calm and rational about Ebola.  In a poll conducted by the venerable Pew Research Center in early October (2-5) only 32% were "very" or "somewhat" worried that they or a member of their family would be exposed to the Ebola virus, and most were confident (58%) in the government to prevent a major U.S. outbreak. However, this was before two cases were reported in the U.S. itself, and public opinion dramatically shifted just a short time later, as people began to focus on the certainty of death that these cases emphasized.  In an October 14th Washington Post-ABC News poll 43% were worried about "the possibility that you or someone in your immediate family might catch the Ebola virus" and 65% were concerned about "a widespread Ebola outbreak occurring in the United States."  Interestingly, most (62%) remained confident in the government's ability to respond to a potential outbreak.

Predictably, there seems to be stronger support for defensive policies that are perceived to mitigate the threat. These include some programs that objectively have a low probability of being effective and may even make matters worse, such as banning travelers to and from African nations hardest hit by the disease (see three excellent analyses of travel bans by Mukherjee, Garrett, and Wolfson).  Despite this, according to the Washington Post-ABC New poll, 67% of Americans now favor travel bans, which seems to demonstrate the power of the "dread" factor over rational analysis.

Perhaps the irony of the Information Age is that having more information hasn't necessarily led to wiser decisions -- in fact, rationality may be more difficult because it requires greater effort to evaluate and to integrate the vast amount of information that is available on virtually any topic. As the title of this blog suggests, we may be slipping into the age of "Unbounded Irrationality" -- unless we pay closer attention to the ways in which we reach conclusions and assess alternatives of action.


SimoneStan said...

The news these days seems to be a constant hype of worst case scenarios whether it is a hurricane, winter storm, or Ebola. Then when you combine that with political rancor and the fall election, you have an administration taken to task by a congress that has repeatedly cut funds to the CDC and still has not approved a surgeon general. And just a week ago halved the requested funds the president asked for to fight Ebola in West Africa.

Don said...

Well done Richard.

Dennis Nord said...

Oh, I like what you did with this, succinct and sharp analysis! Now if we could get everyone to read it and understand and calm down, that would help. Meanwhile, do you think two layers of masking tape at the door will keep ebola out of my house?

Coleen Hanna said...

Dick, I know you are not on Facebook. I am, and my news scroll is screaming with inaccuracies you mentioned. One woman I worked with in my last career sounded as if she was looking for reassurance. I tried to give it to her with some mention of probabilities. She responded with something along the lines of, "Oh I know that but I want to focus on how stupid everyone has been--the government, that nurse, those hospital employees, etc. I hope you don't mind my rant." Despite a lot of examples of past government incompetence (e.g. Katrina, VA hospital system, rollout of Affordable Care Act, and more), people are still quite dependent on the government having no missteps.
I am currently in a medical program at school, and I mentioned in class that Ebola can only be contracted via bodily fluids such as sweat, saliva, semen, blood, etc. Boy did the class turn on me. Someone said that one can contract Ebola by touching a doorknob that someone with Ebola symptoms has touched. The teacher did not correct her.

Richard Sherman said...

Coleen -- that is a little disturbing that your classmates rejected the facts. But then this often seems to be the case these days of willful ignorance. Still, it fits the bounded rationality model very well, as Slovic would point out -- emotional reactions to the "dread" factor lead to overestimates of risk.

BTW I do have a joint Facebook page with my wife -- look for Richard-Karen Sherman.