In general people prefer something freely chosen to the same thing forced upon them. The effect is dramatically revealed in a study that did not directly involve reward or punishment. Lottery tickets costing $1 each were sold to the employees of two companies. Some of the employees were allowed to choose the number of their tickets, others had no choice but were merely handed a ticket. Just before the draw, the experimenter approached each subject offering to buy the ticket back. The subjects who had no choice were prepared to sell back for $1.96 on average, but those who had selected their own tickets held out for an average of $8.67. There could be no better demonstration that we irrationally overvalue what we freely choose.
Excerpt from: Irrationality: The enemy within by Stuart Sutherland