 In 1975, psychologist Daniel Batson from the University of Kansas ran a bold experiment. To a group of young Christians, Batson presented evidence that Jesus Christ did not rise from the dead. Now the evidence wasn't real, it was created for the experiment. Batson wanted to see how the Christians would react. The results were surprising. The left bar here shows the level of religious belief before receiving the evidence. The right bar shows religious belief after the evidence. After people saw evidence that ran counter to their religious belief, their faith actually got stronger. Now why am I talking about a 1970s experiment examining the belief system of young Christians? This study raises a key question. How can people update their beliefs in the opposite direction to the evidence? How can they come to have more faith in their religious belief than before they received evidence to the contrary? This type of response is called the worldview backfire effect. Evidence can backfire if it threatens someone's worldview and it doesn't just apply to religious faith. Let's look at some other examples. One recent study by Brendan Nyhan and his colleagues tested people's intent to vaccinate their children. This graph shows a level of intent to vaccinate for people who are least favourable towards vaccination. The experimenters showed a range of different messages about the importance of vaccination to people who deny the positive benefits of vaccination. The bar on the left here shows the intent to vaccinate amongst a control group who weren't shown any messages. A second group read a message explaining the risks of preventable diseases. As you can see, no difference to the control group. A third group read dramatic narratives about diseases. Again, there was no increase in an intent to vaccinate. A fourth group was shown images of diseases with no significant effect either. And a fifth group read a debunking of the myth claiming that vaccinations led to autism. Debunking the autism myth actually lowered their intent to vaccinate. No matter what message was presented to people predisposed against vaccinations, none increased their intent to vaccinate their children. In other words, for people whose worldview predisposed them to oppose vaccination, no message was successful in changing their minds. In another experiment, researchers presented evidence that there were no weapons of mass destruction in Iraq. Now what effect did this have on participants' belief that there were weapons of mass destruction in Iraq? This graph shows the change in belief after receiving the evidence that no such weapons existed. A negative change in belief below the dotted line means a decrease in belief in weapons of mass destruction. The researchers found that American conservatives became more likely to believe that there were weapons of mass destruction in Iraq. Another example of the worldview backfire effect. We also see the backfire effect with climate change. New stories about the health impacts of climate change backfired among political conservatives. They became less likely to support policies to mitigate climate change. What this research tells us is worldview influences how people respond to new evidence. In other words, it affects how people update their beliefs. We see this with belief in weapons of mass destruction, beliefs about climate change, and religious belief. So let's go back to that 1970s experiment. When Christians were given evidence challenging their faith, their faith got stronger. Forty years later, Professor of Psychology Alan Jern explored what might be happening psychologically to cause such a backfire effect. This research suggested that religious believers expect their faith to be challenged. If someone expects challenges to their beliefs that actually strengthen their belief, then they don't think that those challenges have any validity. This implies that distrust towards the evidence is driving the negative reaction. Nicholas Smith and Anthony Lizerowitz from Yale University ran an experiment that saw this distrust in action. They asked participants for the first words that came to mind when thinking about global warming. Among the people who reject climate change, they saw a range of options, from blaming global warming on natural causes to expressing doubt about the science. But the most common response by far involved conspiracy theories, the notion that global warming was a hoax. There is a significant problem presenting scientific evidence to people who think that science is a hoax. If they think the scientific consensus position is the result of a conspiracy, then any additional evidence supporting the consensus would just be seen as more proof of the conspiracy. So a growing body of research across a range of issues show that evidence that threatens someone's worldview can actually backfire and strengthen people's beliefs. We see this with religious beliefs. Debunking myths about vaccination can actually reduce intent to vaccinate. Presenting evidence of no weapons of mass destruction in Iraq caused conservatives to believe more in weapons of mass destruction in Iraq. And presenting information about climate change caused lower concern about climate change among conservatives. Is there anything we can do about the worldview backfire effect? Researchers have explored various options. One study by David Hardesty and his colleagues tested whether it might be more effective to communicate in a way that doesn't threaten worldview. They used the example of having to pay more for a product in order to help the environment. When the extra cost was framed as a tax, conservatives were less likely to support the price increase. However, if the price increase was framed as an offset rather than a tax, there was equal support for the measure among conservatives and liberals, using language that wasn't threatening to conservatives neutralize the biasing influence of ideology. A second approach suggests that rather than try to convince people about the realities of climate change, communication efforts should focus on mitigation efforts that lead to a better society. Researchers from the University of Queensland presented three different reasons for climate action. The first reason was to avoid environmental and health risks. The green bar shown in this graph is a measure of intent to act environmentally among people who denied global warming. The second reason talked about how climate action would be good for the economy and stimulate more scientific development. This led to a higher intent to act environmentally. The third reason emphasized how climate action would help make people more caring and friendly towards each other. Among people denying climate change, the most effective statement in increasing their intention to act environmentally was the warmth statement. So stepping back and looking at these different lines of research, what does it all mean? Any response to climate science denial needs to recognize what's driving the denial. In many cases the dominant driver is worldview. Engaging with people who deny climate science can result in counterproductive backfire effects or at best a small positive effect when messages are framed in a way that avoids threatening their worldview. Meanwhile, misconceptions originating from climate denial continue to confuse the public. While a proportion of people denying climate science is small, they can influence the large undecided majority. And misconceptions about climate change can erode public support for climate action. Given the stakes, it's important to take a scientific approach to science denial. The science outlines specific characteristics of denial that allow us to distinguish between genuine skepticism and denial. If it is denial promoting misconceptions about climate change, then we need to look at how to protect the public's right to be informed. How do we do that? The evidence tells us that reducing the influence of denial won't happen through engagement with the minority who deny climate science. Instead, it requires communication with the large undecided majority. For this group who are more open to evidence, we need to explain two things, the science of climate change and how that science can be distorted.