I think all of these studies fail to account for the credit component. i.e. I can see that this man I just met has one cookie, but now he's promising me another cookie (which I may or may not be able to see). And then if I do what he says, he'll give me two cookies. What probability do I assign to the chances he can deliver on his promises? Maybe he's a liar. Maybe before I completed the assigned task, he came across a better deal and allocated all his cookies.