Humans are remarkably bad at accurately discerning patterns. All of us (skeptics included) are prone to confirmation biases and logical flaws in reasoning. We don’t like to be wrong, and, as a result, we tend to cling to things that appear to support our preconceived notions, while blindly ignoring things that discredit our views. Even worse, we tend to seek out others who share our views, and we enter echo chambers where we only hear from people who agree with us. This can happen for any of our views, whether they are views on science, politics, religion, etc. and it sets up a dangerous cycle, wherein we first settle on a position, then only accept information that agrees with that position, while simultaneously allowing that information to reinforce our original position. It’s a circle of ignorance that constantly bolsters our view, even if that view is totally incorrect. Again, this can happen to anyone on any topic, but in this post, I want to briefly use anti-vaccers and “vaccine injuries” as an instructive example in how this plays out.

Image via Things Anti-vaccers Say. Also, note that this whole line of reasoning is absurd. DNA doesn’t work the way that they are proposing.

If you ask people who oppose vaccines why they do so, you will likely receive a litany of “vaccine injuries” that they have personally seen or heard reported by others. Some of the more well-known of these include things like autism and SIDs, but the list generally doesn’t stop there. Depending on which anti-vaccer you ask, you may also hear that vaccines cause asthma, allergies, depression, violence, lupus, fibromyalgia, behavioral ticks, shaken baby syndrome, and just about every other issue that you can think off. Indeed, anti-vaccers seem content to view almost everything as a vaccine injury (even homosexuality [again, depending on who you ask]). The Facebook page Things Anti-vaccers Say does a good job of documenting these assertions, and I will include several of their screenshots throughout this post as both examples and discussion points.

Image via Things Anti-vaccers Say

It’s important to pause here to note several things. First, to be clear, vaccines do have side effects (as do all real medical interventions), but those side effects are either extremely mild or extremely rare, and the known benefits far outweigh the risks. Further, most of the things that anti-vaccers blame vaccines for simply are not caused by vaccines. For example, the association between vaccines and autism has been well-studied, and those studies have consistently found that vaccines do not cause autism (details and sources here). Similarly, not only do vaccines not cause SIDs, but they may actually reduce the rate of SIDs (details and sources here [see #64]). This raises the obvious question of why anti-vaccers see vaccine injuries everywhere that they look?

See this post for sources and more details.

Part of the answer is simply a reliance on shoddy sources. Anti-vaccers frequently get their information from notoriously counterfactual websites like Natural News, Green Med Info, Info Wars, and a host of others. Further, they readily accept anecdotes as evidence, which is where the topic of “vaccine injuries” really comes into play. What I see happening over and over again is that one parent tells a tale of how their child received a vaccine then developed autism, started coughing, died from SIDs or shaken baby syndrome, etc., and everyone in the anti-vaccine community makes an astronomical and logically invalid leap to the conclusion that the vaccine was responsible. In reality, however, anecdotes cannot establish causation, and the fact that one event followed another does not mean that the first event caused the second one. Indeed, that line of reasoning is a logical fallacy known as post hoc ergo propter hoc. Things do sometimes just happen to occur together. For example, in a previous post, I looked that the rate of autism and the rate of vaccination and showed that, mathematically, we would expect there to be thousands of cases each year where the first signs of autism were noticed shortly after a vaccination just by chance! This is a major reason why anecdotes aren’t valid evidence: coincidences do happen. Further, using anecdotes for things like vaccines and autism is particularly absurd because of the overwhelming scientific evidence that vaccines do not cause autism. You don’t get to reject a scientific study based on an anecdote. That isn’t how science works.

Note: Many anti-vaccers also site things like VAERS, package inserts, and the VICP, but those are also unacceptable sources for establishing causation as I explained here.

Image via Things Anti-vaccers Say

The explanation that I have just offered seems good at first, but it really just raises more questions than it answers. Most importantly, why are anti-vaccers willing to accept shoddy evidence? This is where confirmation biases come in, and I’d like to use the screenshot to the right as an example. When most people hear a report like this of a “healthy 100-year-old woman dying in six months” (paraphrasing) the cause of death seems pretty obvious: she was 100 years old! It is well established that the very elderly have weakened immune systems and  a reduced ability to recover from illnesses and injuries, and even someone who is in good health (for a 100-year-old) can succumb very quickly to even a minor aliment. Nevertheless, as you can see in the comments, to some anti-vaccers, this had to be a vaccine injury! She received a vaccine (or so they assume) then died a few months later, so the vaccine had to be the cause! (See what I mean about anecdotes being worthless as evidence of causation?)

Image via Things Anti-vaccers Say

I can, of course, give lots of other examples of this, and some are even worse. For example, when faced with evidence that homeopathic teething tablets were potentially causing sickness and even deaths in young children, the anti-vaccer on the left chose to blame vaccines instead. Think about how incredible this is. Here, you have the FDA saying that they have evidence showing that this product is likely dangerous, but instead of listening to the FDA, this anti-vaccer shifted the blame to vaccines despite a complete and total lack of evidence to support that claim! They were so convinced of the evil of vaccines that they were willing to blindly overlook an actual danger and place the blame on vaccines instead.

So, what is going on here? This answer is confirmation biases and, more generally, motivated reasoning. Anti-vaccers believe strongly that vaccines are dangerous, and that belief causes them to see vaccine injuries everywhere. That’s what confirmation biases do: they make you latch onto anything that seems to support your position, even if the evidence is shoddy. Thus, when most of us hear about something like a 100-year-old woman who “suddenly died,” we realize that there are lots of potential causes that are far more plausible than a vaccine, but if you are a committed anti-vaccer, you don’t see those other causes, because they don’t fit your mental narrative. All that you see is the vaccine. Similarly, for the homeopathic anti-vaccer, accepting that a homeopathic product was dangerous didn’t fit their mental narrative, but thinking that vaccines were at fault did fit their mental narrative. So, despite the evidence suggesting that the homeopathic product was dangerous and despite the total lack of evidence to suggest that vaccines were the cause, they blamed the vaccines. That is how powerful confirmation biases and motivated reasoning can be. They can make you think that something dangerous is actually safe and that something safe is actually dangerous.

Although this image is targeted specifically at anti-vaccers, this circle of ignorance can occur for anyone on any topic. Even if your conclusion is correct, it may bias you and cause you to both accept shoddy sources and use those sources to bolster your position.

Now that we have gone over a few examples, let’s turn to what I think is the most dangerous aspect of confirmation biases: their ability to reinforce a belief. Every time that an anti-vaccer sees a non-existent vaccine injury, it reinforces their belief that vaccines are dangerous, which is obviously a big problem. This goes back to the circle of ignorance that I mentioned earlier. For one reason or another, anti-vaccers decided that vaccines are dangerous. Because of that belief, they see “vaccine injuries” that aren’t really there, and those “vaccine injuries” then make them even more convinced that vaccines are dangerous. It is a never-ending circle that sinks them deeper and deeper into ignorance and conspiracy theories. Further, this situation is made even worse by online groups where anti-vaccers can see the anecdotes of other anti-vaccers. Here again, their confirmation biases cause them to blindly accept these stories as evidence against vaccines, even though it is illogical to do so.

At this point, you may be ready to laugh at anti-vaccers for being stupid, but you shouldn’t be. As I have previously argued, most people who reject science aren’t stupid or crazy, they are just misinformed and have succumbed to their confirmation biases and motivated reasoning. Importantly, this is not a problem that is limited to science-deniers. It is a problem that affects everyone. All of us are prone to confirmation biases, and we all should constantly check our views to make sure that we are following facts and logic rather than following what we want to be true. We need to carefully consider evidence rather than blindly latching onto the things that fit our mental narratives. Perhaps most importantly, we should always consider the possibility that we are wrong. Being willing to be wrong is (in my opinion) the only way to break the circle of ignorance. Unless you are actually willing to be wrong, you will never be able to accept evidence that is contrary to your beliefs, and it is important that you are capable of doing that. To quote an excellent Dr. Who episode, “the circle must be broken.”

Note: Please do not use the VAERS, package inserts, or VICP as evidence unless you have read this post.

Note: You may be wondering how a homeopathic tablet could be dangerous since they are usually just water, so here is the story in a nutshell. This product is supposed to contain very tiny amounts of belladonna, a substance which is quite harmful in higher doses (as is true of many active ingredients in homeopathy). However, the dose makes the poison, so when diluted to extremely low levels (as homeopathic products generally are) this product is harmless (it’s also useless, but that’s beside the point). However, the FDA kept receiving numerous reports of children becoming sick or even dying after taking the tablets, and the symptoms matched the known symptoms of belladonna poisoning. So, the FDA started investigating, and they found that the amount of belladonna in the tablets was inconsistent, which is a huge problem because, as I said, this chemical is toxic at higher doses. So, it is extremely important that it only be present in very low doses. Thus, although this does not conclusive demonstrate that the homeopathic tablets were at fault, the combination of inconsistent doses of a potentially toxic chemical and the fact that children who took it where experiencing the symptoms of receiving a high dose of that chemical certainly makes a good case against the homeopathic product. Again, a more proper study is necessary for a conclusive answer, but the evidence is certainly strong enough that parents should take it seriously, and blindly rejecting that evidence in favor of arbitrarily blaming vaccines is insane. Finally, please note that this is a very different situation from the anecdotes that parents use against vaccines, because those anecdotes are all over the map, don’t match the symptoms of vaccine ingredients at the doses at which they are present, and frequently fly in the face of actual studies. In most cases, there is no plausible mechanism through which the vaccine could be at fault.