The image of an angel and a devil sitting on a person’s shoulders is not a bad metaphor for shopping.

Using brain scans, researchers have shown that the nucleus accumbens, an area associated with pleasure and reward, lightens up as people consider a purchase, while the insula, a structure that plays an important role in pain, is activated when they think about the cost.

Two brain areas compete with each other to determine whether you will buy something. Your typical tightwad feels the pain of paying for things more acutely. Spendthrifts may not register it enough.

Buying a lot in one store can decrease your sensitivity to the pain of cost. You hit the what-the-heck-effect. For example, you’ve spent $200; what’s another $20 for a T-shirt? Perhaps, the best way is going to various stores for different purchases.