On Vaccines 2: Risky Feelings

Author's Note: I request you remember the ground rules for this post: I am taking it as a given that vaccines are effective and safe. If you would like to dispute this fact, then please review this obnoxiously hyperlinked sentence.

What keeps people from vaccinating their kids against potentially deadly vaccine-preventable diseases (VPDs)? In the last post we discussed how we make medical decisions.  A classical model of decision-making is that a person measures the risks and benefits and makes a choice based on which is greater. While true in a limited sense, this theory does not tell the whole story.  Last time we examined how a human brain evaluates the benefits of vaccinating.  Here we will discuss the hugely important topic of risk assessment and its role in judgment and decisions.

The Experiential and Analytical Systems

Figure 1: The Experiential and Analytical Systems.  

(Slovic et al., 2004)

            Since risk assessment is a mental process, we need to discuss the structure of our mind before we continue.  In recent decades, cognitive psychologists have described two different, parallel systems that we use to make decisions.  The first system is the Experiential system (ES)⁵ which utilizes associations, intuitions, and emotions to make decisions.  It is quick to make judgments and loathe to verify them.  It extrapolates from minimal information and integrates the data in the larger context of what is known, felt, and thought (Figure 1).  The second system is the analytical system (AS).  It is logical and methodical in its evaluation of data.  It is slower than ES and responsible for fact checking it.  It is concerned with being correct, not quick.  ES tends to be the process we use more in everyday decisions.  It can be very reliable when the patterns and associations it’s evaluating are familiar.   We see 8 kinds of peanut butter on the grocery store shelf.  ES knows we like the Jif with the red cap and striped label and quickly identifies it.  AS evaluates information more carefully.  Money may be tight, so you look at 2 different HEB coupons - one gives 20 cents off sausage flavored mayo if you buy two Jif cans the other gives two free bags of potting soil if you buy the HEB brand peanut butter – and AS decides which is the best deal. 

           

Thinking Errors

The important thing to understand about both systems is that they each have weaknesses.  To think quickly, ES employs mental shortcuts, “heuristics,” which are prone to make predictable errors in judgment, “biases” (the main subject of Kahneman’s award-winning book Thinking Fast and Slow³ which I shall reference frequently).  In the peanut butter example, you employed a pattern recognition heuristic that said, “red top and striped label = Jif”.  While most likely a reliable conclusion, the fact remains that a knock-off brand could use similar packaging.  To confirm its authenticity you have to read the label. Cheap brands might find that 1 in 10 people do not check the label and exploit this heuristic for their own gain by selling red-topped “Piff”.  We discussed heuristics in the last post while talking about benefits of vaccination.  Vividness, immediacy effect, and affective reasoning all fall in this category.  Heuristics also play an important role in risk evaluation, as we shall see below, and are worth understanding to avoid making erroneous judgments.

            AS’s weakness is that it is lazy.  It is often content to let ES draw the conclusions, especially if the conclusions “feel right,” what psychologists call “cognitive ease”³.  You end up with inferior Piff peanut butter in your basket because AS was content with the available information; the packaging, the size of the jar, the syllables and cadence of the name were consistent with Jif.  Had it been so inclined, it could have made you slow down to read the label to check its accuracy.  It could have gone on to evaluate whether cheaper Piff was a more intelligent purchase than more expensive Jif and avoided the disappointment you will feel at home when your sandwich tastes like cardboard.  In this instance, its contentment with its cognitive ease superseded its desire to be correct. 

            Below we will talk about how ES and AS evaluate risk.  We will talk about ES more because I believe its activity impacts everyday risk evaluation more than AS.  Plus, we are assuming that vaccinations are proven safe and effective.  This is an AS conclusion based on evidence and logic; a conclusion outside the scope of this post (see the linked up disclaimer above.)

Affect Heuristic

            We discussed the affect heuristic in the last post, except I called it “affective reasoning” because we didn’t have the language of heuristics.  Affect, our feelings toward a topic, dramatically alters perceptions of risks and benefits.  Paul Slovic, one of the foremost researchers in this area, demonstrated an inverse relationship between our perceptions of risks and benefits based on our affect: positive feelings magnify benefits and diminish risk while negative feelings do the opposite⁵.  Researchers demonstrated this by measuring people’s response to information about either the risks or benefits of nuclear power.  If a person was convinced that the benefits were higher for nuclear power, they downplayed the risks.  If they were told the benefits were low, then the risks were perceived as higher.  The same relationship was true for risk perception – information describing nuclear power as more risky decreased the perceived benefits and information describing nuclear power as less risky increased the perceived benefits⁶.  

These findings are due to how ES integrates the information, including emotional information, pertaining to the topic “nuclear power”.  You see, ES has a habit of answering questions it is not asked, particularly if it can answer an easier question instead of a harder one³.  The question “is nuclear power safe?” could be answered by evaluating safety data of power plants in a country, disease rates near the plant, security information, etc., but this is information that is either not available to ES or requires lazy AS to compute.  If ES can instead answer the easier question, “how do I feel about nuclear power?” then it can arrive at a conclusion! Its favorite thing! And in general, you feel good about things that have many benefits and little risk and you feel bad about risky things with little benefit.  Therefore, if you feel good about nuclear power, then you will tend to think it is a great technology that does not pose a threat to society.  This relationship holds for quick judgments requiring ES (the same researchers showed this relationship increases under time pressure⁶), so if you’re reading this and thinking that you can see how it is beneficial AND risky, you’ve engaged AS in the discussion and are no longer using the affect heuristic.

      This has compelling implications for vaccine acceptance.  The negative portrayal of vaccines has gained prevalence in our culture.  Even if you love vaccines, you’ve heard the negative propaganda and thought how frightful it would be if it were true.  Vividness comes into play here.  Just as we discussed before that VPDs are not prevalent and therefore not very vivid, so autism, autoimmune disease, crying children, or whatever your vaccine injury of choice are quite prevalent and quite vivid.   Such negative images have a way of clawing into our brains and nesting there.   

Imagine a Well-Meaning Mommy who has heard the scary, negative propaganda about vaccines, but between 3 kids and 8,000 dirty diapers, has not had time to critically evaluate the information.  She comes into my clinic and I say its time for shots! At that moment in her brain, ES’s eyes pop open.  ES looks around suspiciously, thinking it’s heard something about vaccines before, and spots the TV interview with super hot whatsherface who said something about toxins and hurt children.  It also recalls the conversation with a fellow mommy proudly raging against vaccines for whatever reason. ES acknowledges these memories aren't necessarily reliable information; however, what is reliable is that these interactions make her feel uncomfortable toward vaccines.  Mom begins to feel a rising discomfort that she can’t quite put her finger on.  I happily explain to her all the great benefits of preventing VPDs, unaware that such statements sound empty to her compared to the growing dread of shoving a needle into her child and giving her toxins.  She politely declines, saying she’s just not comfortable with vaccines at this moment.  Mildly surprised, I ask what makes her uncomfortable.    With growing confidence she says she feels they’re risky and she’s not sure if her child needs them.  I sit back dejectedly, wishing she had read this blog post so we could discuss the affect heuristic. 

People’s stated reasons for vaccine refusal differ widely, but it is surprising how frequently I hear “I’m not comfortable”, as if your intuitive feeling alone is a good reason to ignore over 100 years of vaccine research.  Such is the power of the affect heuristic - positive and negative feelings not only convince us to make decisions based on little evidence, but also, once decided, create justifications for it.    

More on our cognitive relationship to risk in the next post.

References

1. Smith PJ, Humiston SG, Marcuse EK, et al. Parental Delay or Refusal of Vaccine Doses, Childhood Vaccination Coverage at 24 Months of Age, and the Health Belief Model. Public Health Reports. 2011;126(Suppl 2):135-146.
2. Rottenstreich Y, Hsee CK. Money, kisses, and electric shocks: On the affective psychology of risk. Psychological Science. 2001;12(3):185-190.
3. Kahneman D. Thinking, fast and slow. Macmillan; 2011.
4. Cappelen A, Mæstad O, Tungodden B. Demand for Childhood Vaccination – Insights from Behavioral Economics. Forum for Development Studies. 2010;37(3):349-364.
5. Slovic P, Finucane ML, Peters E, MacGregor DG. Risk as analysis and risk as feelings: Some thoughts about affect, reason, risk, and rationality. Risk analysis. 2004;24(2):311-322.
6. Finucane ML, Alhakami A, Slovic P, Johnson SM. The affect heuristic in judgments of risks and benefits. Journal of behavioral decision making. 2000;13(1):1-17.
7. Lichtenstein S, Slovic P, Fischhoff B, Layman M, Combs B. Judged frequency of lethal events. Journal of experimental psychology: human learning and memory. 1978;4(6):551.
8. Medicine Io. Adverse Effects of Vaccines: Evidence and Causality National Academies Press 2012.