Have you ever ended the month with a larger credit card balance than you expected? If you’ve ever had substantial credit card debt, in retrospect, would you ever have taken out a loan up-front to make those same purchases?

The painless experience of paying by credit card, and the uncertainty of how much your bill will actually be at the end of the month lead to an almost natural abuse of credit cards argues George Loewenstein, neuroeconomist at Carengie Mellon.

Remember, neuroeconomists are those morphing neurologists working to determine how our emotions and natural cognitive biases affect decisions that pure economic theory predicts will be totally rational. (And if you think spending is rational, I encourage you to go shoe-shopping with my friend Melody. You will end the adventure entirely disabused of rational markets theory.)

When you use a credit card, Loewenstein notes, it just doesn’t generate that same feeling of giving something up. This is supported by a marketing professor’s study at the University of Toronto (Dilip Soman) indicating people far more often tend to underestimate, or even fail to recall, how much they’ve spent when they pay by credit card versus cash. Worse yet, this lack of spending conciousness tends to lead us to slide passively into debt Loewenstein argues, rather than by explicit decision that the purchase is worth taking on the debt and paying the item’s total interest-inflated cost.   

When I compare this to my own tendencies, it rings true. For example, if I take out my budgeted allowance for groceries in cash, the very act of watching that pile of cash dwindle and carefully adding up purchases in my head to make sure they don’t exceed the cash in my pocketbook, makes it much easier to say no to things we might like, but don’t need.

Which also makes me wonder, if I were a merchant, could I increase sales by providing stronger suggestion or incentive to pay by credit card? Now there is a study for testing in a down market.

Have you ever been deciding to make – or not make – a purchase when suddenly you were interrupted? Maybe you were on your computer and the phone rang, or you were in the store and the salesperson had to leave before finishing the answer to your question. When you got back to making your decision, what happened?

If you’re like me, and apparently a lot of other people, when you get back to that decision, you find your questions have a different focus. New research from Wendy Liu of UCLA shows that while your initial consideration is often bottom up, a detail-oriented, and price-conscious process, an interruption will flip your decision to one that is more top-down, goal-oriented, and price-insensitive.

In other words, after even a brief interruption, you’re more likely to focus on quality, satisfaction, and desirability than on feasibility and price, says Liu. So be forewarned, if you’re about to make a major purchase and are worried about price, remember to recalibrate after those interruptions to make sure you’re still considering feasibility.

And if you’re selling higher priced items that differentiate on quality and other measures of desirability, you might consider the impact of a brief interruption.

“Whether you choose to have an exotic vacation, invest in high-risk stocks, or buy that big plasma TV may depend on whether you were interrupted when making the decision,” writes Liu.