What really kills people?

Of course the first thing that one will say is that people die from Ebola. Yes, that’s true, but people die from a lot of things. Let’s consider the following facts from the CDC for causes of death in the United States:

• Number of deaths: 2,515,458

• Death rate: 807.3 deaths per 100,000 population

• Life expectancy: 78.7 years

• Infant Mortality rate: 6.07 deaths per 1,000 live births

Number of deaths for leading causes of death:

• Heart disease: 596,577

• Cancer: 576,691

• Chronic lower respiratory diseases: 142,943

• Stroke (cerebrovascular diseases): 128,932

• Accidents (unintentional injuries): 126,438

• : 84,974

• Diabetes: 73,831

• Influenza and Pneumonia: 53,826

• Nephritis, nephrotic syndrome, and nephrosis: 45,591

• Intentional ( ): 39,518

Now the first thing to realize is that only one person has died in the USA from Ebola and it is someone who contracted it in Libera. That’s no guarantee that other people won’t die, but there are over 325 million people in the country. So far, the odds are pretty low.

But few people are watching news stories about the fear of heart disease, cancer, respiratory illness, stroke and accidents, even though these are the most common causes of death. And, in many cases, early death from these diseases can be avoided by lifestyle changes, such as , exercise, moderation, and eliminating . But we don’t panic about these long-standing causes of death, the American waistline continues to expand and a recent article tells us that death from liver disease in the UK has increased over 40% in the past 12 years—mostly due to overdrinking. Other highly risky behaviors—such as not wearing a seat belt, smoking, over-spending, unprotected , dangerous driving---which kill people, lead to unwanted pregnancies or bankrupt people—are all preventable and controllable. But we don’t worry. Why?

The answer may be in how we misperceive risk—and this is where the cognitive science of risk perception is important. Part of this is that once we activate a concept—like “Ebola”—our minds naturally search for examples of the feared disease. This is known as “ ” and leads us to focus on more information about Ebola, a tendency to discount evidence against the threat, and relying on our emotions to estimate risk.

Once the threat system is activated it looks for more threat. We are now in the “better safe but sorry mode” so we are reacting intensely, quickly, and emotionally looking for more evidence that we are at greater risk. We get angry at people who try to put things in perspective because this is equated with letting our guard down and endangering everyone.

Let’s define risk as the likelihood of an occurrence given exposure. And let’s throw in the degree of consequence. So, the risk of being killed in a car accident would be the number of miles you drive and the likelihood of being killed that year. And the consequence here would be death. That sounds perfectly rational, but that’s not how most people think. We use rules of thumb—or “ ”—to estimate risk. So let’s look at them.

The Misperception of Risk

Recency

The more recent a negative event, the more likely we think it will happen again—and soon. So, Ebola is the new “kid” on the block, so it seems more risky. But the real risk is all the other illnesses and risks in the neighborhood for the past 50 years--- smoking, , drinking, etc.

Familiarity

We just get used to things being around. So we are used to cancer, stroke, heart disease, accidents. And getting used to something means to us that it is less risky.

Cumulative exposure

Similar to familiarity, the longer we engage in a behavior—like smoking, drinking, driving without seatbelts—the lower the perceived risk. People say, “I never wear a seatbelt and I am still alive”.

Emotional Reasoning

One form of misperception of risk is to base our fears on how we feel. “I don’t know what the odds are but I feel so it must be dangerous”. This circular reasoning can lead us to judge the likelihood of danger on how we feel. So, if you feel anxious on a plane you might think it’s dangerous to fly which makes you more anxious. An interesting corollary of the emotion heuristic is that if something feels good we underestimate risk and if it doesn’t feel good we over-estimate risk. So smoking and drinking lead to lower perception of risk while getting a vaccination leads to higher perception of risk.

Salience

The more dramatic the threat the greater the perceived risk. So salience can include the fact that we hear all the bad news all the time about Ebola—it’s very salient. Or the pictures of dead bodies in Africa leave a lasting impression. The more salient, the more perceived risk.

A picture is worth a thousand probabilities

If you can put a picture out there it makes the risk more memorable—and appear to be more risky. So along with the salience, we might add that images are far more emotional than probabilities—which are abstract. if you want to make someone worried, show a video of people with Ebola. But psychologists know that most people are “guilty” or “probability neglect”---we don’t think about abstractions, we think about stories, photos, images, voices.

Invisibility is threatening

Our threat-detection system treats an invisible threat as a greater risk. You can’t see Ebola coming at you—like you could a car on the highway. This sense of an invisible threat adds to our estimation of danger. If you can’t see it, you think you can’t prevent it.

Representativeness

We now think that a fever is “representative” of “a symptom of Ebola”, something that almost no one in Dallas thought about three months ago. So we now are scanning for the “signs” and “triggers” of Ebola and we will misperceive someone sneezing, fatigued, or simply African as the walking death that will kill all of us. But we didn’t always think this way. Now they are “representative” of Ebola.

Perception of chain reactions

Part of the current threat perception is the belief that one occurrence that involves “800 people exposed” is the same as 800 people contracting Ebola and then a chain reaction so that each person in the feared sequence will infect 800 more. If you do the calculations you will eventually exceed the population of the United States. But there is no evidence of this chain reaction here.

Misconstruing uncertainty

Along with all of these misperceptions is the belief that uncertainty means a bad outcome and until we know for sure we are all at risk. Of course, logically that would mean all of us is always at risk since no one is omniscient. But when the threat system is activated we now believe that uncertainty almost guarantees a catastrophe. People might say, “OK, so the chances are 100 million to one—but I could be that one”. Well, that’s true and you would be a very unlucky person if that happened. But that’s not how you think about driving a car, flying in an airplane, or eating a hotdog. You say, “Come on, I’ll take my chances”.

Search for safety behaviors

The frightened person will not simply rely on their threat detection--- he or she will try to do something. This could involve wearing a mask, avoiding public transportation, praying, getting yourself checked out by a doctor, or seeking reassurance. You momentarily feel safe. But then your emotional brain “reasons”---“The risk is still there. You simply survived because you did those safety behaviors”.

When you are listening to the news, think about the fact that there are 325 million people without Ebola here and that you are probably facing more danger by eating that hotdog and drinking an extra beer. Risk is often in the eyes of the beholder.