Economists always find data elicited from surveys very suspect. Unless money or actual decisions are on the line, people may say anything. For non-monetary matters, this is particularly important problem, as there is no market observation that can provide more reliable data.
Nicolas Jacquemet, Robert-Vincent Joule, Stéphane Luchini and Jason Shogren look whether a simple trick can provide a more truthful revelation of preferences: a survey under oath. They test this with a second-price auction and find it works better than anything else. Very interesting and intriguing. One wonders how the cultural background of respondents may matter here. For example, religious people may take oaths more seriously, and they may also have preferences that differ in a systematic way.