The problem with opportunity cost is that opportunity cost is divided among many, many things.

But suppose we are nothing more than the sum of our first, naive, random behaviors. What then?

What people do is they pay the small loans first. Why? Because they enjoy making the number of loans smaller. But of course it is a very ineffective way to pay debt down.

We're actually trying to develop an iPhone app, now that the Droid is out, we'll do it for that as well, if we ever learn how to program on this thing. But the idea is that to make money concrete. So, you can do this app, and it's not out there, but you can do the app. And you say, "I like vacation in the Bahamas, shoes, lattes, and books." And now, when you are tempted to buy something, that thing translates in terms of the things you are interested in.

Money is all about opportunity cost. Every time you spend on something, that's something you can't spend on something else.

I don't want to say that the poor are inherently cognitively diminished, but at the end of the day of making difficult, tough decisions, it's very hard to have the energy to think about things with the right mindset.

The bad news is that ignoring the performance of people is almost as bad as shredding their effort in front of their eyes. Ignoring gets you a whole way out there. The good news is that by simply looking at something that somebody has done, scanning it and saying "Uh huh," that seems to be quite sufficient to dramatically improve people's motivations.