There is no doubt that free, or zero anything, really, is an attractive proposition. What Ariely underscores is that this can be attributed to anything. We don't just like free things to the extent to which we will sacrifice our time and energy to obtain them, but we also like working for free too. Ariely conducted studies where MIT volunteers who were asked to do a problem were much more independent and willing to help than paid students. Ariely explains this through social and market norms, indicating that when money is involved, rationality kicks in, and it is merely a matter of input and output.