In fact, that's covered in the article:
"The results can explain the growing tendency of consumers to overspend when purchasing items with credit cards instead of cash, because consumers do not immediately pay for items charged to credit cards and the "pain" of the potential loss is minimized."
Slashdot Mirror
No, no, what you do is cut down the trees and burn them for energy!
In fact, that's covered in the article: "The results can explain the growing tendency of consumers to overspend when purchasing items with credit cards instead of cash, because consumers do not immediately pay for items charged to credit cards and the "pain" of the potential loss is minimized."