Predictably Irrational: The Hidden Forces That Shape Our Decisions

by Dan Ariely

to the extent that we all believe in human rationality, we are all economists.

most people don’t know what they want unless they see it in context.

think it’s because humans are intrinsically afraid of loss. The real allure of FREE! is tied to this fear. There’s no visible possibility of loss when we choose a FREE! item (it’s free).

In other words, our participants worked harder under the nonmonetary social norms than for the almighty buck

Because once market norms enter our considerations, the social norms depart.

Gifts are also effective for sofas, and offering people a gift, even a small one, is sufficient to get them to help; but mention what the gift cost you, and you will see the back of them faster than you can say market norms.