Why do a small minority of people cling onto debunked theories and myths about vaccines, despite overwhelming scientific and medical evidence about their benefits? We asked a cognitive psychologist to explain the science of misinformation.
Juniper Russo is a self-confessed 'crunchy' mum. Like most mothers in her natural parenting community, she uses cloth nappies, feeds her children healthy organic foods, and breastfeeds.
For a while, she also refused to vaccinate her children.
"I thought 'I'm a natural mum and this is how I raise my baby and if I use cloth diapers and if I breastfeed, then that means I also have to choose not to vaccinate," she said over the phone from Chattanooga, US.
"I felt like I just had to go along with what all the other mums in my community were doing."
"I heard people saying that vaccines were dangerous. It was very easy to mistake that for real science. It was really easy to fall into this trap of mass hysteria."
As a young mother, who fell pregnant at 20, Ms Russo said she was naïve and scared of the challenges ahead.
"I didn't know how to tell good information from bad information. So I got very easily misled by this subculture of natural parenting and I got swept into the fear – which is what led me to make those mistakes.
"I wanted to believe that children are completely safe without vaccines," the 27-year-old mother of two said. "I heard people saying that they were dangerous. It was very easy to mistake that for real science. It was really easy to fall into this trap of mass hysteria."
In February, an unvaccinated 18-month-old boy died from measles in Berlin, Germany. This was the first known fatality among more than 570 recorded measles cases in the German capital since October 2014. The resurgence of the preventable disease in Germany, as well as in parts of the United States, coincides with a movement among some parents to refuse to vaccinate their children.
The so-called anti-vaccination movement in which fears about potential side effects of vaccines, fuelled by now-debunked theories suggesting a link to autism, have led a small minority of parents to refuse to allow their children to be inoculated.
Relying on 'mental rules of thumb'
Cognitive psychologist Dr Ullrich Ecker from the University of Western Australia studies the science of misinformation. He said he isn’t surprised that a small minority of people are rejecting scientific facts for anecdotal evidence.
With the deluge of information we are faced with nowadays, Dr Ecker explained, it’s increasingly difficult for people to effectively process scientific evidence with clarity.
Instead of spending time critically analysing information – which takes up precious cognitive resources – people turn to what’s familiar.
"We turn to 'heuristics' – mental rules of thumb to make decisions and what to believe and what not. So they ask themselves: 'How does [this information] fit in with what I already believe? What do others believe? What is relevant to me, my peers and my friends?'"
This is a normal cognitive process, he added. But it can be problematic if what you and your peers believe is wrong, and not back by scientific evidence.
When misguided beliefs turn into an identity
One logical fallacy that can lead people down the vaccine myth 'rabbit hole' is what scientists call 'confirmation bias'. This is the idea that people will selectively look for evidence or information that supports what they already believe.
"So if you're faced with ambiguous information then you'll also try and interpret things that confirm the way you already think or what you already believe."
The confirmation bias also explains why people will often cite dubious websites and blogs to validate their views – regardless of gaping factual or scientific inaccuracies.
"People nowadays get lots of information from the internet. They will stay on websites where they know they will find information that is in line with what they already believe.
"There's also a lot of distrust. If you're staying within your circle of believers then you start mistrusting people from the outside."
By this point, Dr Ecker said, misguided beliefs can turn into an identity that people feel is worth defending.
"If you believe something very strongly, that is a big part of identity. And if that is challenged, it's about defending your identity… And if you hang around likeminded people, it becomes about defending your tribe, so to speak."
"People pay a lot of attention to who they trust, and I think people should put more trust into people that actually have expertise."
Ms Russo agrees that her anti-vaccine sentiment was mainly about defending her identity.
"When you've got all of your crunchy mum friends who are choosing not to vaccinate… you don't want to be the one who goes against the grain within that community," she said.
"You don’t want to think that you've done something that could've led to your child getting measles and dying. So there's kind of this knee jerk response that if somebody says, 'oh our baby's in danger.' You want to say, 'No he's not.' And then you want to cling onto it even harder.
"Which is why I feel like even in the face of insurmountable evidence, a lot of parents are still clinging to the anti-vaccine movement. I think a lot of it is herd mentality."
It was only when her daughter was diagnosed with development delays at four months – before she was old enough to get vaccinated – that Ms Russo realised her mistrust of vaccines was baseless.
"It was very clear to me that [my daughter's] autism was not caused by vaccines," she said. "I had an 'Ah ha' moment and realised that I had been very mistaken, and that [my] hesitance about vaccines was unfounded."
Ms Russo said trusting her paediatrician ultimately changed her mind.
"I started on the other side of the fence, and now I'm very far in the other direction," she said. "Like, once I figured out my mistake and realised how much I had been duped, and how easy it is to fall prey to these misconceptions that have the potential to kill children."
Changing existing beliefs 'difficult'
While possible, Ms Russo's stance from being an 'anti-vaxxer' to a 'pro-vaxxer' isn't common.
Studies have shown that changing someone's mind about vaccines or climate change is incredibly rare. In fact, a 2014 study published in Pediatrics showed that trying to 'talk some sense' into an anti-vaxxer could backfire and actually make matters worse.
Dr Ecker said changing an existing belief is difficult, since beliefs are strongly driven by familiarity. "Things that are familiar are more easily, more readily believed."
Regarding the myth that vaccines cause autism, he said: "By repeating those concepts and the link between those concepts, I actually make that link more familiar.
"What they remember is, 'they said something about vaccines and autism' and then that link has been strengthened, it's more familiar, and hence people continue to use it."
'Trust me, I’m not an expert'
A 2013 study published in the Journal of Applied Research in Memory and Cognition has also suggested that people tend to change their mind on issues if they trust the source, irrespective of that person’s expertise on the subject.
As the researchers noted, expertise alone was not enough to sway someone’s opinion or misinformation. On the other hand, a trustworthy source "significantly" decreased the participant’s use of incorrect information.
"The expertise doesn't really matter all that much. What really matters is whether or not you trust that person," Dr Ecker said of the study. "To me personally, that's a bit scary. Because I would think that if you have a medical issue, you should talk to your GP and not your uncle Bob.
"People pay a lot of attention to who they trust and I think people should put more trust into people that actually have expertise."
"Skepticism is a really really good thing, and I encourage everyone to be skeptical about what they see."
The overwhelming majority of scientific and medical evidence supports the benefits of vaccines. In 2014, a major international review found no evidence linking the development of autism with commonly-used vaccines for measles, mumps, rubella, diphtheria, tetanus and whooping cough.
The Global Alliance for Vaccines and Immunisation (GAVI) in January announced that $US7.5 billion ($A9.45 billion) had been pledged from countries and private donors to help immunise 300 million more children in developing countries over the next five years. The funding will help the alliance, created in 2000 as an international public-private partnership, support developing countries in vaccinating an additional 300 million children, saving up to six million lives.
"The evidence is pretty clear, in the scientific community, there's a strong consensus on what's going on," Dr Ecker said. "Just like they understood very well back in the 1950s that tobacco caused lung cancer, but it took two or three decades until that made its way into common knowledge."
Fostering healthy skepticism
To counteract misinformation, cognitive psychologist Dr Ecker recommends fostering a healthy dose of skepticism in all aspects of life.
"Skepticism is a really really good thing, and I encourage everyone to be skeptical about what they see. Look at the evidence and decide for themselves. Sometimes it's good to take a step back and say, 'why do I actually believe that? What's the actual evidence?'"
Having turned her back on the anti-vaccine movement, mother of two Juniper Russo is encouraging all parents to scrutinise the scientific evidence for and against vaccines.
"I understand how scary it is, I understand what it's like when you're given all kinds of contradictory information and you feel like you just can't win. I know what a tricky position it is to be in because I've been there.
"But I also know as a mum of a child who was autistic before she was vaccinated – as a mum who has learned to trust science and my paediatrician - I can really say that vaccines are overwhelmingly safe. They're certainly far safer than the condition that they treat."