Good parents are protective of their children and fear things they think could do them harm. Unfortunately, parents (like anyone else) can be mistaken about what is and is not harmful. This can occur because, ironically, people tend to reason poorly when they are afraid. This is ironic because such situations are when we really need our reasoning skills the most. One such situation is the controversy over vaccines and autism.
Dr. Paul Offit recently wrote a book on the subject, Autism’s False Prophets: Bad Science, Risky Medicine, and the Search for a Cure, that has generated a great deal of controversy. One of the purposes of the book is to address the alleged causal link between vaccines and autism. His position, which is well supported by the weight of scientific research, is that vaccines do not cause autism and are safe for children.
Despite the fact that the weight of evidence shows that vaccines (including the thimersol that was once used as a preservative in some vaccines) do not cause autism, many people still believe there is a connection. Part of this is due to the fact that a now retracted 1998 study suggested a link between vaccines and autism. Part of this is due to the fact that lawyers, celebrities, and people in the media continue to claim that there is a connection. Even John McCain asserted his belief in the connection. In some cases, these people are honestly mistaken. In other cases, they stand to benefit from such claims.
Not surprisingly, Offit is the target of anger and even threats. In the case of people who are willfully misleading the public, this is to be expected. In the case of people who are honestly mistaken, this might seem surprising. After all, one would think they would be grateful to know the truth. Of course, there are those who doubt that Offit has the truth.
Offit’s critics contend that he stands to gain financially from vaccines and hence is biased. Offit profited from the sale of the vaccine RotaTeq and has also been a paid and unpaid consultant for the drug company Merck (which now manufactures RotaTeq).
From a critical thinking standpoint, this concern is reasonable. After all, a person’s credibility is reduced to the degree that they are biased and money is a strong biasing factor. When people raise this concern, they are reasoning well-provided that they are raising it on good grounds and not as a rationalization for their rejection of his claims.
While money is a biasing factor, when assessing the credibility of a source it is also important to consider the whole picture and not just one factor. To do otherwise would be fall victim to a bias. Offit’s personal history and behavior seem to indicate that he is more concerned about the well being of children than about money and people do speak highly of him. These factors might very well offset any bias from his financial ties to vaccines and, of course, his scientific credentials are quite solid.
Fortunately, resolving the key issue (whether vaccines cause autism or not) does not depend on Offit’s credibility alone. There has been extensive research into the alleged connection between vaccines and autism and, as noted above, the weight of the evidence is overwhelmingly against there being a meaningful connection. Why, then, do people still believe that there is a connection?
First, as mentioned above, there are celebrities, people in the media, lawyers and others who claim that there is a connection. People are often bad at discerning between legitimate authorities on a subject and people speaking on that subject who are famous for something else (like being an actor). When people make this error they are committing a fallacious appeal to authority.
Second, people are generally poor at scientific reasoning and critical thinking. Even college educated people. My own university’s assessment process revealed that most of our students are weak in these areas and similar assessment at other schools have revealed similar results. These results match my own experiences teaching critical thinking. When people are not very good at scientific reasoning and critical thinking, they tend to not know how to assess such research and also tend to be less influenced by logical arguments. Instead, they tend to be more influenced by emotional factors and poor reasoning. This leads to the third reason.
Third, people are more influenced by their emotions than by reason. Many parents are worried that their child will develop autism. Thus, fear and love leads them to be concerned about anything that might cause autism. These emotions can impede their ability to assess the matter rationally and they can come to feel that vaccines are a threat when they hear about the connection. If they are not good at critical thinking, they will not be able to properly investigate the matter and hence will tend to stick with how they feel rather than finding out what would be most rational to think.
Fourth, most people tend to be more influenced by poor reasoning than by good reasoning. As I tell my students, fallacies tend to be far more persuasive than logical arguments. After all, people tend to feel far more strongly than they think. Further, people tend to fall into very predictable patterns of poor reasoning and accept the results as true.
In the case of autism and vaccines, people seem to fall into the post hoc fallacy. This allacy derives its name from the Latin phrase “Post hoc, ergo propter hoc.” This has been traditionally interpreted as “After this, therefore because of this.” This fallacy is committed when it is concluded that one event causes another simply because the proposed cause occurred before the proposed effect. In the case at hand, parents might notice their child showing signs of autism after receiving vaccinations and assume that the vaccinations are the cause. However, without adequare evidence linking the two, this would not be a reasonable inference.
Fifth, when people do not know what is causing something harmful, they can start grasping at explanations. People, sensibly enough, do not like being ignorant of what is causing autism. While this does motivate people to search for a cause, it can also lead people to simply pick an explanation so that they now feel more in control. Of course, if someone does not have a good grasp of critical reasoning, they can accept something as a cause that really is not. For example, people have explained illnesses and deaths in terms of witchcraft, curses and vampires. Today, few people would attribute autism to supernatural causes, but taking vaccines as the cause without adequate evidence can be seen as somewhat similar: a cause (or scapegoat) must be found to make people feel better.
Does this mean that vaccines have no possible link to autism and the people who worry about it are foolish? No, clearly not. There could be cases in which a vaccine has triggered autism by interacting with many other factors and it is reasonable to be concerned about such a possibility. However, it is also important to approach the matter rationally and not let fear lead people into making unwise choices.
After all, while there is the possibility that vaccines might have some link to autism, it is well established that vaccines protect children from very real harms. Some parents, afraid of the alleged link, have not vaccinated their children or are not following the recommended schedules. Given the serious consequences of some of these diseases, a failure to vaccinate properly could be very harmful to the children. Naturally, these vaccines should be made as safe as possible.