People can be tricked into reversing their opinions on moral issues, even to the point of constructing good arguments to support the opposite of their original positions, researchers report today in PLoS ONE.

The researchers, led by Lars Hall, a cognitive scientist at Lund University in Sweden, recruited 160 volunteers to fill out a 2-page survey on the extent to which they agreed with 12 statements — either about moral principles relating to society in general or about the morality of current issues in the news, from prostitution to the Israeli–Palestinian conflict.

But the surveys also contained a ‘magic trick’. Each contained two sets of statements, one lightly glued on top of the other. Each survey was given on a clipboard, on the back of which the researchers had added a patch of glue. When participants turned the first page over to complete the second, the top set of statements would stick to the glue, exposing the hidden set but leaving the responses unchanged.

Two statements in every hidden set had been reworded to mean the opposite of the original statements. For example, if the top statement read, “Large-scale governmental surveillance of e-mail and Internet traffic ought to be forbidden as a means to combat international crime and terrorism,” the word ‘forbidden’ was replaced with ‘permitted’ in the hidden statement.