Ben Goldacre, The Guardian, Saturday 3 July 2010

What do people do when confronted with scientific evidence that challenges their pre-existing view? Often they will try to ignore it, intimidate it, buy it off, sue it for libel, or reason it away.

The classic paper on the last of those strategies is from Lord in 1979: they took two groups of people, one in favour of the death penalty, the other against it, and then presented each with a piece of scientific evidence that supported their pre-existing view, and a piece that challenged it. Murder rates went up, or down, for example, after the abolition of capital punishment in a state, or comparing neighbouring states, and the results were as you might imagine. Each group found extensive methodological holes in the evidence they disagreed with, but ignored the very same holes in the evidence that reinforced their views.

Some people go even further than this, when presented with unwelcome data, and decide that science itself is broken. Politicians will cheerfully explain that the scientific method simply cannot be used to determine the outcomes of a drugs policy. Alternative therapists will explain that their pill is special, among all pills, and you simply cannot find out if it works by using a trial.

How deep do these views go, and how far do they generalise? Professor Geoffrey Munro took around a hundred students and told them they were participating in a study on “judging the quality of scientific information”, now published in the Journal of Applied Social Psychology. First, their views on whether homosexuality might be associated with mental illness were assessed, and then they were divided into two groups.

The first group were given five research studies that confirmed their pre-existing view. Students who thought homosexuality was associated with mental illness, for example, were given papers explaining that there were more gay people in psychological treatment centres than the general population. The second group were given research that contradicted their pre-existing view. (After the study was finished, we should be clear, they were told that all these research papers were actually fake, and given the opportunity to read real research on the topic if they wanted to).

Then they were asked about the research they had read, and were asked to rate their agreement with the following statement: “The question addressed in the studies summarized… is one that cannot be answered using scientific methods.”

As you would expect, the people whose pre-existing views had been challenged were more likely to say that science simply cannot be used to measure whether homosexuality is associated with mental illness.

But then, moving on, the researchers asked a further set of questions, about whether science could be usefully deployed to understand all kinds of stuff, all entirely unrelated to stereotypes about homosexuality: “the existence of clairvoyance”, “the effectiveness of spanking as a disciplinary technique for children”, “the effect of viewing television violence on violent behavior”, “the accuracy of astrology in predicting personality traits”, and “the mental and physical health effects of herbal medications”.

Their views on each issue were added together to produce one bumper score on the extent to which they thought science could be informative on all of these questions, and the results were truly frightening. People whose pre-existing stereotypes about homosexuality had been challenged by the scientific evidence presented to them were more inclined to believe that science had nothing to offer, on any question, not just on homosexuality, when compared with people whose views on homosexuality had been reinforced.

When presented with unwelcome scientific evidence, it seems, in a desperate bid to retain some consistency in their world view, people would rather conclude that science in general is broken. This is an interesting finding. But I’m not sure it makes me very happy.