A detailed analysis of more than 22K subjects in 42 separate psychology studies demonstrates this startling result. The simple act of telling people they don’t have to do something makes it much more likely they will. In the studies, subjects donated more money to charity, agreed more readily to participate in a survey, and gave more to someone asking for a bus fare home.
This ‘But You Are Free‘ effect is based on the fact humans become more closed-minded when their choices are reduced by others. Explicitly giving people the right to say no reaffirms our freedom to choose. In psychological terms, the appearance of choice increases compliance to a request.
The exact phrase used is not critical; “but obviously do not feel obliged” works just as well as “but you are free.” While significantly stronger when done in person, this effect even works in print or in email. As a result, marketers should consider including these phrases in the call-to-action portions of campaigns.
You should follow me on twitter (@jbecher) but you are free not to.