In general, we want to be honest, but fear and other emotions often form a roadblock for truth when thought comes to action. When you need to get accurate information out of someone, putting the signature block at the top of a form gives them the nudge they need towards honesty.
Photo by Ken Teegardin.
Wired Science points to an interesting study by Northwestern University psychologist Lisa Shu that discovered this phenomenon.
To see whether this signature effect could be harnessed to reduce cheating, Shu's team enrolled 101 college students and employees in performing two self-reported tasks: solving maths problems correctly in exchange for money, and claiming reimbursements for expenses on a library trip. For each task, test participants filled out a claims form. Some signed at the bottom, others at the top, and others didn't sign at all. Top-signers reported solving fewer problems, and claimed fewer expenses, than the other groups.
Shu's study isn't the first to discover that inciting honesty requires a reminder. Dan Ariely points to a study in his book Predictably Irrational that discusses how recalling the 10 commandments prevented cheating on tests. The study concludes, same as Shu's, that a reminder to be honest is enough to make people honest. When you need truth, just remember to ask for it.