As I was cruising the news this morning I came across a fantastic article about shopping. It detailed the findings from studies done by Stanford professors. (I loved that part too. My DH spent over five years there and my DD1 took part in their children's studies.)
I won't go into the details of it, but it gives a lot of good scientific details about how the brain reacts to spending, what factors drive spending, how credit cards are dangerous and how we justify spending more when we use them, etc., etc.
Here is the link http://www.cnn.com/2009/LIVING/personal/08/13/o.six.shopping.traps/index.html?iref=werecommend