Recruiting a sample of Americans via the internet, they polled participants on a set of contentious US policy issues, such as imposing sanctions on Iran, healthcare and approaches to carbon emissions. One group was asked to give their opinion and then provide reasons for why they held that view. This group got the opportunity to put their side of the issue, in the same way anyone in an argument or debate has a chance to argue their case.
Those in the second group did something subtly different. Rather that provide reasons, they were asked to explain how the policy they were advocating would work. They were asked to trace, step by step, from start to finish, the causal path from the policy to the effects it was supposed to have.
The results were clear. People who provided reasons remained as convinced of their positions as they had been before the experiment. Those who were asked to provide explanations softened their views, and reported a correspondingly larger drop in how they rated their understanding of the issues. (more; paper; HT Elliot Olds)
The question “why” evokes a far mode while “how” which evokes a near mode.