Vaccine dispute from a psychological perspective


Published: 11-02-2020

Last modified: 29-03-2020

There has long been a dispute over the safety of vaccines on the internet and in the media. It started with thimerosal vaccines that are supposed to cause autism, but recently I have been hearing more and more voices about the harmfulness of all vaccinations. I don’t want to stand on either side in this article. However, I want to explain some of the psychological mechanisms that can be seen in those involved in discussions on this subject and that make both sides of the dispute unable to convince the other party.

Confirmation bias

Confirmation bias is a very well-known phenomenon in psychology. It is a tendency to seek information that confirms our previous beliefs about a topic and to reject information that conflicts with our beliefs. As a result of this tendency, it is difficult for us to prove that we are wrong about something and we rarely change our minds.

In one study of this mechanism (Lord et al., 1979), supporters and opponents of the death penalty were asked to read two texts. One of the texts gave arguments for the death penalty and the other against it. Both were written in scientific style and based on sources. On the basis of both texts, one could conclude that the issue of the effectiveness of the death penalty in deterrence of potential criminals is complicated and it is difficult to clearly determine whether the death penalty is effective or not. Subjects, however, came to different conclusions. Proponents of the death penalty became even more convinced that it should be carried out and in the text giving arguments against it they were looking for various minor errors or methodological shortcomings, and similarly opponents of the death penalty – the text that gave arguments for the death penalty was not credible in their opinion and as a result they confirmed their previous belief.

This mechanism can also be seen in supporters and opponents of vaccines. Both sides of the dispute meet with sources about the harmfulness and safety of vaccines. Proponents of vaccination, however, consider sources that cite opponents as unscientific, fictitious or manipulated, in response they provide links to articles from scientific journals, to which opponents of vaccination respond with the argument about funding research by pharmaceutical companies and claim that these sources are made up or manipulated. It is easier for both opponents and supporters to believe those sources that can confirm their beliefs, which is why attempts to convince the other party to their argument are not very effective.

The need for cognitive closure

There is plenty of information on the safety level of vaccines on the Internet and other sources. However, hardly anyone will go to the trouble of reaching at least most of this information and verifying the sources provided. Most will read only a small portion of information on the basis of which they form an opinion, often extreme, and will then defend it. This is due to the need for cognitive closure and intolerance of ambiguity, which is one of its components. In short – many of us don’t like to don’t know something. Sometimes we prefer to form an opinion on a given topic using a selective portion of information than to admit that we do not know.

The need for cognitive closure is a desire to have clear and certain knowledge about a given topic. In psychological jargon, it is a desire to reduce the feeling of cognitive uncertainty. Underlying this need are two processes: first, we “capture” information, and then “freeze” it in our cognitive structures, that is, in our “knowledge base”.

On the one hand, some situational factors influence the need for cognitive closure. One of such factors is time – if we have little time to make a decision and we need some knowledge or our own opinion to make it, our need for cognitive closure will obviously be greater in such a situation.

On the other hand, the need for cognitive closure is also a personality trait, i.e. in some people it is generally at a low level, in others at a high level and in most people at a more or less average level. This trait consists of 5 factors:

  • Preference for order and structure
  • Desire for predictability
  • Discomfort with ambiguity
  • Close-mindedness
  • Decisiveness

For each of us, the above features occur to a greater or lesser extent.

People with a high need for cognitive closure like order and predictable situations known to them. They also usually have a high level of ambiguity intolerance. This is a feature that describes how we approach ambiguous, e.g. contradictory or incomplete information on a given topic. It not only refers to the search for knowledge, but also to other aspects of life, e.g. the assessment of other people. People with a high level of intolerance of ambiguity often have a problem in recognizing that one person may have both disadvantages and advantages, and generally tend to perceive the world in black and white colors, and in ambiguous situations they usually quickly choose one solution and stick to it. Such people will therefore not be willing to read conflicting information about vaccine safety. They will form an opinion on this topic faster than people who tolerate ambiguities better and stick to their opinions more tightly.

People with a high need for cognitive closure are also characterized by low mind-openness, i.e. they are reluctant to other, new beliefs, ideas, etc. They are also usually decisive, that is, they make decisions faster than people with a low need for cognitive closure and are more certain that they have chosen correctly.

The high level of the need for cognitive closure therefore favors a superficial analysis of the incoming information. The resulting picture is often simplified, but it provides a sense of clarity and predictability, which ensures comfort for such people. Their belief system is rigid and resistant to change, they usually form an opinion quickly on a given topic and are more likely to be subject of confirmation bias. They are usually resistant to persuasion, that is, it is difficult to impose their opinion on them. This does not apply only to the situation in which they first come across a given issue. In this case, they strive to form an opinion on the subject as soon as possible, so their resistance to persuasion will be low.

People with a high need for cognitive closure are also more likely to have the primacy effect. It is a tendency to form your opinion based on the first information you hear and insensitivity to later information.

In addition, they are characterized by low openness to experience. This is a feature describing how we approach various novelties, how much we like to acquire new knowledge, etc. People with high openness to experience also tend to take unconventional and non-schematic actions, they are also characterized by high autonomy and independence in the formulation of judgments and in making decisions.

In contrast to the high, low level of the need for cognitive closure, it creates conditions for a thorough analysis of the situation and openness to new information. Such people are less likely to quickly formulate final judgments on a given topic, better tolerate uncertainty, and are happy to consider alternative interpretations of a given situation. So they will be more likely to read conflicting information about the risks and benefits of vaccinations, may hesitate and have a problem deciding whether to vaccinate their child or not, and will not resist changing their minds if they receive new information.

People with a high level of cognitive closure are, however, both among opponents and among proponents of vaccination. So what causes some to find themselves among opponents and not supporters? This can be explained by belief in conspiracy theories and the availability heuristic.

Belief in conspiracy theories

It’s no secret that some research is funded by pharmaceutical companies. However, proving that such studies are manipulated, or moreover, that all studies that confirm vaccine safety have been manipulated by pharmaceutical companies is no longer easy. So why do some believe this and others don’t?

Studies show that some are particularly keen to believe in different conspiracy theories and this is due more to their general beliefs than to knowledge of a particular event. In psychology, there is even talk of “conspiracy mentality“.

Wood et al. (2011) conducted two studies on this topic. In the first study, participants were asked to indicate how much they agree or disagree with various conspiracy theories. They concerned the WTC attack, global warming, moon landing and the death of Princess Diana. Three statements about the death of Princess Diana were mutually exclusive. Two of them contained conflicting information about who killed her, and the third said her death was a fraud and she is still alive. It turned out that belief in these theories positively correlated with each other. The more someone believed that she was murdered, the more he/she believed that she was still alive. To better investigate this phenomenon, the researchers conducted another study on a different group of people. This time they asked about belief in various theories about the death of Osama bin Laden. Again, it turned out that belief in the information that bin Laden was already dead when the authorities announced that he had died in the operation of American commandos correlated positively with the belief that he was still alive. Studies suggest, therefore, that some people tend to believe in any conspiracy theory, and this is due more to their general belief that authorities or the media are hiding something rather than information gathered about a particular theory.

There are some features that correlate with conspiracy mentality. This means that people who easily believe in conspiracy theories can be expected to have these traits, but of course this may not always be the case.

One of them is a sense of powerlessness – people who have this trait often feel helpless and admit that life problems overwhelm them. People with conspiracy mentality also often have an anomy, i.e. the view that the modern world is too complex and incomprehensible, as well as a high level of hostility and anxiety and a low level of trust. Often, one may notice in them a high level of external locus of control, i.e. the belief that their lives are driven by factors independent of them.

What’s more, belief in conspiracy theories also has to do with the need for cognitive closure. Although, as I mentioned above, people with a high need for closure do not necessarily have to be an extreme opponent of vaccination, but research shows that in people who believe in conspiracy theories, this feature is more often at a high level. Conspiracy theories often give simple explanations for a complicated problem, which gives such people comfort.

And what seems to me the most important in the context of vaccination – belief in conspiracy theories increases under stress (that’s why people who are generally fearful are more susceptible to believing in them). This is important because parents worry about their children, they want the best for them, that’s why stories about children who have autism or other serious complications after vaccination cause fear and then there is a greater chance that they will believe in conspiracy theory behind this story.

Availability heuristic

Heuristics are simplified methods of reasoning that all of us involuntarily use. This is normal and healthy, because every day our mind must process a lot of less and more important information and every day we make many less and more important decisions: buy this cheese or that, go to the gym, on a bike or maybe to the cinema, where go on vacation, take this loan or not, vaccinate a child or not … We are not able to base our every decision on an in-depth data analysis. If it wasn’t for heuristics, we wouldn’t do anything, just analyze everything all day long, still not ready to make a decision. Heuristics are therefore needed, while their side effects are cognitive biases, i.e. errors in our reasoning.

For example, anchoring and adjusting heuristic is making a decision based on easily accessible information, often suggested by others (“anchor”) which is adjusted to a given situation. Reasoning biases resulting from this heuristic are used, among others by sellers when negotiating prices. If the seller gives the price, say 1000, we probably won’t answer that we will buy this thing for 200, but rather that for 800. We “anchor” at the price and do not thoroughly analyze how much the product really is worth.

Another common heuristic, called representativeness heuristic, consists in assigning an object (e.g. persons, things, phenomena) to a given category on the basis of features considered characteristic (representative) for a given category, bypassing statistical procedures. This is well explained in the study of Kahneman and Tversky (1972). They informed the study participants that short descriptions of members of a certain group were created, which included 70 engineers and 30 lawyers. Then they gave them to read descriptions of the members of this group, one of which like this: “John is a thirty-year-old married man with two children. He is active in local political organizations. His hobby is collecting rare books. He is eloquent, convincing and competitive.“. They were then asked if they thought John was probably an engineer or lawyer. Most people answer such a question that he is probably a lawyer, although the calculation of probability shows otherwise.

We also have availability heuristic, which seems to me the most important in the context of reluctance to vaccinate. It is overestimating the probability of events that are more available to our memory. Usually these are events that we have heard a lot about in the media, the Internet or learned from a friend and that strongly affect emotions. Such events are, for example, plane crashes – they are widely presented in the media and strongly affect emotions. That is why many people are afraid to fly planes and are not afraid to drive cars, despite the fact that accident statistics indicate that driving a car is associated with a higher risk of a fatal accident.

Vaccination complications are also such events. It’s not difficult to find photos or stories of children with complications on the internet. They can be searched on Google or found on Facebook, where some see them as shares from their friend. Such information causes parents to fear for their child, and in result vaccination complications seem for them more likely than statistics suggest. In addition, in anti-vaccine groups or websites it can be seen that they very often use stories / photos of specific children. Such messages always arouse more emotions than statistics presented by vaccination supporters.

Mechanisms such as confirmation bias, the need for cognitive closure, and belief in conspiracy theories are also present on other controversial topics, e.g. GMOs or climate change. In the case of vaccines, however, additional emotion is provided by the fact that it is about the safety of children. It is obvious that parents want the best for their child and worry about it, which is why information about complications evokes such strong emotions in them, which in turn often makes it even more difficult to do cold data analysis.

Therefore, the dispute over vaccine safety will continue for a long time and one should not expect that in the near future supporters will be able to convince opponents or opponents will be able to convince supporters.


  1. Abalakina-Paap M., Stephan W. G., Craig T. , Gregory W. L. (1999). Beliefs in Conspiracies. Political Psychology, 20(3), 637-647. (pdf on
  2. Bruder M., Haffke P., Neave N., Nouripanah N., Imhoff R. (2013). Measuring individual differences in generic beliefs in conspiracy theories across cultures: Conspiracy Mentality Questionnaire. Frontiers in Psychology, 4(225), 1-15. (text on
  3. Grzesiak-Feldman M. (2013). The Effect of High-Anxiety Situations on Conspiracy Thinking. Current Psychology, 32(1), 100-118.
  4. Kahneman D., Tversky A. (1972). Subjective probability: A judgment of representativeness. Cognitive Psychology, 3(3), 430–454.
  5. Kossowska M. (2003). Różnice indywidualne w potrzebie poznawczego domknięcia. Przegląd Psychologiczny, 46(4), 355-373. (pdf on
  6. Lord C. G., Ross L., Lepper M. R. (1979). Biased assimilation and attitude polarization: The effects of prior theories on subsequently considered evidence. Journal od Personality and Social Psychology, 37(11), 2098-2109. (pdf on
  7. Marchlewska M., Cichocka A., Kossowska M. (2018). Addicted to answers: Need for cognitive closure and the endorsement of conspiracy beliefs. European Journal of Social Psychology, 48(2), 109-117.
  8. Norton R. W. (1975). Measurement of Ambiguity Tolerance. Journal of Personality Assesment, 39(6), 607-619.
  9. Ophoff H. W. (2001). Intolerance of Ambiguity – two empirical studies on the generality concept and their heuristic implications. Folia Psychologica 5, 35-58. (pdf on
  10. Myślenie i rozumowanie w: J. Strelau, Psychologia. Podręcznik Akademicki, tom 2., Gdańskie Wydawnictwo Psychologiczne, Gdańsk 2004.
  11. Swami V., Furnham A., Smyth N., Weis L., Ley A., Clow A. (2016). Putting the stress on conspiracy theories: examining associations between psychosocial stress, anxiety, and belief in conspiracy theories. Personality and Individual Differences, 99, 72-76. (pdf on
  12. Umam A.N., Muluk H., Milla M.N. The need for cognitive closure and belief in conspiracy theories: An exploration of the role of religious fundamentalism in cognition. Diversity in Unity: Perspectives from Psychology and Behavioral Sciences – Ariyanto et al. (Eds) © 2018 Taylor & Francis Group, London, ISBN 978-1-138-62665-2. (pdf on
  13. Webster D. M., Kruglanski A. W. (1994). Individual Differences in Need for Cognitive Closure. Journal of Personality and Social Psychology, 67(6), 1049-1062. (pdf on
  14. Wood, M. H., Douglas, K. M., Sutton, R. M. (2011). Dead and Alive: Beliefs in Contradictory Conspiracy Theories. Social Psychological and Personality Science, 3, 767-773. (pdf on

Author: Maja Kochanowska

Add comment

Time limit is exhausted. Please reload CAPTCHA.

Newest comments