Public opinion change vs. moral arguments
Public opinion change vs. moral arguments

Our study shows that the connection between a certain moral position and the type of argument that is raised in its defence, can predict what opinions will gain ground", says Pontus Strimling, researcher at the Centre for Cultural Evolution and the main author of the paper.

Together with Irina Vartanova, Fredrik Jansson and Kimmo Eriksson – mathematicians, psychologists and social scientists at Stockholm University and the Institute for Futures Studies – he has built mathematical models based on new findings within moral psychology, and used these to predict opinion changes on moral issues over time. The predictions were then compared with over 40 years of data on public opinion. Their conclusion is that the key characteristic of opinions that gain ground is that they are supported by arguments about what is fair and what does not cause harm to others.

"The connection is very clear. And the model can be used to make qualified assessments about the future", says Pontus Strimling.

Opinions based on other classical grounds used to determine right and wrong actions – loyalty, authority, purity, religion – can gain support temporarily, but over time opinions based on these arguments lose support all over the political spectrum. The stronger the connection an opinion has to arguments about fairness and harm, the greater is the probability that it will gain ground in the public opinion. Also, the stronger the connection is, the faster the change will come.

Pontus Strimling. Photo: Sara Moritz

"This can explain why public opinion have changed so rapidly in favour of gay and lesbian rights. Arguments in favour of same sex marriage, for instance, are based on principles of fairness, while arguments against are based on authority and purity. Over time the latter arguments lose support. On other issues, such as support for active euthanasia or to ban pornography, there are powerful arguments on both sides, so change is slower", says Pontus Strimling.

You can read the full paper in Nature Human Behaviour here.

74 predictions on moral and political development

The researchers have studied 74 issues. Use the tool below to see the researchers' predictions on how opinion will change in each issue.