Neuroscience
By guest blogger Simon Oxenham
Over recent years, measles has once again become a public health crisis in the western world as a result of growing anti-vaccination movements in the UK and the US. This is an enormous problem because the success of vaccination depends on herd immunity: unless the vast majority of the population is protected, vaccines cannot halt the rapid spread of infectious diseases, leaving vulnerable people at risk, such as those with immune disorders, the elderly and newborn babies.
Efforts to encourage vaccine uptake have been hampered by a curious psychological phenomenon: the Backfire Effect. Research by Brendan Nyhan and Jason Reifler published this year demonstrated that efforts to persuade people to vaccinate their children can backfire, and actually reduce intentions to vaccinate. Now a new study, published yesterday in PNAS, has investigated further, adapting Nyhan and Reifler’s methodology.
A core problem in combating anti-vaccine views is that it is very hard to prove absence of risk, much in the same way that it is impossible to prove there isn't a cosmic teapot orbiting the sun. The authors of the new study, led by Zachary Horne, hypothesised that a better approach would therefore be to focus on convincing parents that without vaccinating, the risk of contracting vaccine-preventable diseases is high and the consequences severe.
First a quick re-cap on an earlier 2014 study by Nyhan and colleagues that provided the inspiration for the new research. Nyhan’s group compared the effects of four different types of evidence: 1) Correcting misinformation about the MMR vaccine; 2) Information about the risks of measles, mumps and rubella; 3) Parents’s reports on their children being infected with these diseases; and 4) Images of children infected with the diseases.
Nyhan's team found that none of these forms of evidence alone increased parents’ intentions to vaccinate their children. The effects of the information about measles, mumps and rubella were surprisingly neutral, while the images of infected children and the mother’s narrative about her hospitalised child both had the unintended effect of increasing beliefs in vaccine side-effects. The images also managed to inadvertently increase false beliefs that vaccines cause autism. The material that refuted the MMR-autism link successfully reduced false beliefs, but also reduced the intent to vaccinate in parents with the most anti-vaccine beliefs (i.e. there was a backfire effect). The overall picture was complex to say the least.
For the new study, Horne and his team combined the different information presented in the 2014 research to create a “disease risks condition” that included a mother's narrative of their child experiencing infection, alongside information about the effects of the diseases, as well as the images of the infected children. The comparison condition provided evidence contradicting the myth that MMR causes autism, and a control group read information that was irrelevant. Participants were hundreds of parents and non-parents surveyed online.
Contrary to the 2014 study, Horne’s team found that informing participants of the risks of failing to vaccinate did have a meaningful effect on parents’ beliefs about vaccines. This compared favourably to the information that debunked false beliefs about autism and the MMR vaccine, the effect of which did not differ significantly from the control condition. In this study neither intervention led to a backfire effect.
The results are encouraging, and indicate that a backfire effect is not unavoidable when communicating information about vaccine safety. The study is, however, not without its limitations. The study didn't directly evaluate intention to vaccinate – this is an important factor, as Nyhan’s 2014 study found that debunking false beliefs successfully reduced misperceptions about vaccines, but at the same time had the effect of reducing intentions to vaccinate in the very same people! In their 2014 paper they even remarked "if we had not measured intent, we might have missed a potentially dangerous backfire effect". The same researchers replicated this finding earlier this year in the context of flu. It seems a design flaw of the new Horne et al. study that this effect wasn't evaluated.
In response to the paper, Nyhan and Reifler remarked: "We’re excited to see the Horne et al. PNAS article on the effect of messages promoting vaccines and hope to see more experimental studies like this in the future. In addition, we’re encouraged that they find messages about the dangers of communicable diseases are effective in improving vaccine attitudes. Future research should consider the extent to which design differences between the two studies help explain the somewhat different conclusions the two studies reach, which will help us reach our shared goal of better understanding vaccine attitudes and behavior."
While the new research sounds like good news all round, celebration may be premature. The findings don't even get close to the bottom of the mystery that is the backfire effect; they don't explain the complexities teased out in earlier research, and they don't show that behaviour to vaccinate or not vaccinate would have changed. At a time when anti-vaccine beliefs are making a comeback, understanding and avoiding the backfire effect is more important than ever.
The next step for researchers will likely involve working out how we can make a powerful enough argument to convince the hard core of people with fixed anti-vaccine beliefs to vaccinate their children. The final step, and perhaps most difficult of all, will be ensuring that the change in beliefs stands the test of time.
_________________________________
Horne, Z., Powell, D., Hummel, J., & Holyoak, K. (2015). Countering antivaccination attitudes Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1504019112
--further reading--
The “Backfire Effect”: Correcting false beliefs about vaccines can be surprisingly counterproductive
Post written by Simon Oxenham for the BPS Research Digest. Simon Oxenham covers the best and the worst of the world of psychology and neuroscience on his Neurobonkers blog at the Big Think. Follow @Neurobonkers on Twitter, Facebook, Google+, RSS or join the mailing list.
The Research Digest free fortnightly email will keep you up-to-date with all the psychology research we digest: Sign up!
- Why Is It So Hard To Persuade People With Facts?
An effective way to correct people’s falsely held beliefs is to address them directly with evidence. However, such rebuttals can sometimes backfire, leading people to double-down on their original position. A new paper published in Discourse Processes...
- Strong Reassurances About Vaccines Can Backfire
Unwarranted public anxiety about vaccinations can have deadly consequences. Unfortunately, the challenge of communicating health risks is full of psychological complexity. A new German study brings this home, showing how messages that deny vaccination...
- The Psychological Barriers Facing Mmr Promotion Campaigns
A focus group study of parents' attitudes towards interventions promoting uptake of the MMR vaccine suggests it is better for health advice to be seen as independent from government. The findings come after the General Medical Council ruled yesterday...
- How To Promote The Mmr Vaccine
Rather than stressing its benefits, health promotion campaigns for the MMR vaccine should emphasise the protection that is lost by failing to have a child inoculated. That's according to Purva Abhyankar and colleagues who said finding the most effective...
- Meningitis And Prevnar
CDC Lifts Limits on Meningitis Vaccine By THE ASSOCIATED PRESS (copyright) 16 September 2004 Filed at 1:20 p.m. ET ATLANTA (AP) -- Replenished supplies of a childhood meningitis vaccine has prompted health officials Thursday to lift a previous recommendation...
Neuroscience
Researchers say they've found a way to combat anti-vaccine attitudes, but is it premature to celebrate?
By guest blogger Simon OxenhamOver recent years, measles has once again become a public health crisis in the western world as a result of growing anti-vaccination movements in the UK and the US. This is an enormous problem because the success of vaccination depends on herd immunity: unless the vast majority of the population is protected, vaccines cannot halt the rapid spread of infectious diseases, leaving vulnerable people at risk, such as those with immune disorders, the elderly and newborn babies.
Efforts to encourage vaccine uptake have been hampered by a curious psychological phenomenon: the Backfire Effect. Research by Brendan Nyhan and Jason Reifler published this year demonstrated that efforts to persuade people to vaccinate their children can backfire, and actually reduce intentions to vaccinate. Now a new study, published yesterday in PNAS, has investigated further, adapting Nyhan and Reifler’s methodology.
A core problem in combating anti-vaccine views is that it is very hard to prove absence of risk, much in the same way that it is impossible to prove there isn't a cosmic teapot orbiting the sun. The authors of the new study, led by Zachary Horne, hypothesised that a better approach would therefore be to focus on convincing parents that without vaccinating, the risk of contracting vaccine-preventable diseases is high and the consequences severe.
First a quick re-cap on an earlier 2014 study by Nyhan and colleagues that provided the inspiration for the new research. Nyhan’s group compared the effects of four different types of evidence: 1) Correcting misinformation about the MMR vaccine; 2) Information about the risks of measles, mumps and rubella; 3) Parents’s reports on their children being infected with these diseases; and 4) Images of children infected with the diseases.
Nyhan's team found that none of these forms of evidence alone increased parents’ intentions to vaccinate their children. The effects of the information about measles, mumps and rubella were surprisingly neutral, while the images of infected children and the mother’s narrative about her hospitalised child both had the unintended effect of increasing beliefs in vaccine side-effects. The images also managed to inadvertently increase false beliefs that vaccines cause autism. The material that refuted the MMR-autism link successfully reduced false beliefs, but also reduced the intent to vaccinate in parents with the most anti-vaccine beliefs (i.e. there was a backfire effect). The overall picture was complex to say the least.
For the new study, Horne and his team combined the different information presented in the 2014 research to create a “disease risks condition” that included a mother's narrative of their child experiencing infection, alongside information about the effects of the diseases, as well as the images of the infected children. The comparison condition provided evidence contradicting the myth that MMR causes autism, and a control group read information that was irrelevant. Participants were hundreds of parents and non-parents surveyed online.
Contrary to the 2014 study, Horne’s team found that informing participants of the risks of failing to vaccinate did have a meaningful effect on parents’ beliefs about vaccines. This compared favourably to the information that debunked false beliefs about autism and the MMR vaccine, the effect of which did not differ significantly from the control condition. In this study neither intervention led to a backfire effect.
The results are encouraging, and indicate that a backfire effect is not unavoidable when communicating information about vaccine safety. The study is, however, not without its limitations. The study didn't directly evaluate intention to vaccinate – this is an important factor, as Nyhan’s 2014 study found that debunking false beliefs successfully reduced misperceptions about vaccines, but at the same time had the effect of reducing intentions to vaccinate in the very same people! In their 2014 paper they even remarked "if we had not measured intent, we might have missed a potentially dangerous backfire effect". The same researchers replicated this finding earlier this year in the context of flu. It seems a design flaw of the new Horne et al. study that this effect wasn't evaluated.
In response to the paper, Nyhan and Reifler remarked: "We’re excited to see the Horne et al. PNAS article on the effect of messages promoting vaccines and hope to see more experimental studies like this in the future. In addition, we’re encouraged that they find messages about the dangers of communicable diseases are effective in improving vaccine attitudes. Future research should consider the extent to which design differences between the two studies help explain the somewhat different conclusions the two studies reach, which will help us reach our shared goal of better understanding vaccine attitudes and behavior."
While the new research sounds like good news all round, celebration may be premature. The findings don't even get close to the bottom of the mystery that is the backfire effect; they don't explain the complexities teased out in earlier research, and they don't show that behaviour to vaccinate or not vaccinate would have changed. At a time when anti-vaccine beliefs are making a comeback, understanding and avoiding the backfire effect is more important than ever.
The next step for researchers will likely involve working out how we can make a powerful enough argument to convince the hard core of people with fixed anti-vaccine beliefs to vaccinate their children. The final step, and perhaps most difficult of all, will be ensuring that the change in beliefs stands the test of time.
_________________________________
Horne, Z., Powell, D., Hummel, J., & Holyoak, K. (2015). Countering antivaccination attitudes Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1504019112
--further reading--
The “Backfire Effect”: Correcting false beliefs about vaccines can be surprisingly counterproductive
Post written by Simon Oxenham for the BPS Research Digest. Simon Oxenham covers the best and the worst of the world of psychology and neuroscience on his Neurobonkers blog at the Big Think. Follow @Neurobonkers on Twitter, Facebook, Google+, RSS or join the mailing list.
The Research Digest free fortnightly email will keep you up-to-date with all the psychology research we digest: Sign up!
- Why Is It So Hard To Persuade People With Facts?
An effective way to correct people’s falsely held beliefs is to address them directly with evidence. However, such rebuttals can sometimes backfire, leading people to double-down on their original position. A new paper published in Discourse Processes...
- Strong Reassurances About Vaccines Can Backfire
Unwarranted public anxiety about vaccinations can have deadly consequences. Unfortunately, the challenge of communicating health risks is full of psychological complexity. A new German study brings this home, showing how messages that deny vaccination...
- The Psychological Barriers Facing Mmr Promotion Campaigns
A focus group study of parents' attitudes towards interventions promoting uptake of the MMR vaccine suggests it is better for health advice to be seen as independent from government. The findings come after the General Medical Council ruled yesterday...
- How To Promote The Mmr Vaccine
Rather than stressing its benefits, health promotion campaigns for the MMR vaccine should emphasise the protection that is lost by failing to have a child inoculated. That's according to Purva Abhyankar and colleagues who said finding the most effective...
- Meningitis And Prevnar
CDC Lifts Limits on Meningitis Vaccine By THE ASSOCIATED PRESS (copyright) 16 September 2004 Filed at 1:20 p.m. ET ATLANTA (AP) -- Replenished supplies of a childhood meningitis vaccine has prompted health officials Thursday to lift a previous recommendation...