We all stroll into the supermarket each week, and sometimes stroll out with lots of grocery items we never intended to buy.  Why?  One reason may be if we are buying those groceries on a credit or debit card.

"The next time you go food shopping, hit the ATM first. In a simulated shopping session, people using credit or debit cards spent 70% more on junk food than cash customers did, but spent about the same amount on healthy foods, a study in the "Journal of Consumer Research" found. You feel less "wallet pain" when you use abstract forms of payment like credit and debit cards, and this may weaken your ability to control impulse purchases, according to the study."

(Men's Health)