This kind of foolish frugality is common. Consider how easy it is to fritter away time surfing the web for, say, a great deal on a $50 pair of jeans. Yet many of us spend no time at all on our investments. The result is that we barely glance at the fees charged by mutual funds: Without thinking much about it, we will choose a fund that charges an extra 0.25 percentage point rather than spend the time to find a cheaper one. That’s reasonable on the face of it. What’s a quarter of a percent? But that seemingly tiny percentage difference can easily amount to thousands of dollars of lost money. We brag to our friends about how much we saved on the jeans — “30 percent off!” — never mentioning (or even registering) the money we threw away on our investments.

Another of Professor’s Azar’s papers summarizes the problem perfectly: “Do Consumers Make Too Much Effort to Save on Cheap Items and Too Little to Save on Expensive Items?” The answer is, resoundingly, “Yes.”

Complicating matters is the fact that marketers understand this all too well. When you go to buy a new car, at the very end of the transaction, the dealer may suggest some add-ons. And you may be tempted to bite. Once you’re paying tens of thousands of dollars, what’s an extra $200 for a better sound system? It’s not just a problem with car sales. When you’re buying a $1,000 computer, why quibble over a little extra for a bigger hard drive? Or when you’re choosing a large flat-screen TV, why not pay a little more for one that is a few inches bigger?

This is a slippery slope. Once you have gotten started, substantial sums can feel small. If you have remodeled your home recently, this may be painfully familiar.

What all of this amounts to is a tendency to think in relative rather than absolute terms. In some ways, what we experience as consumers is like what we experience when we listen to music or lift a heavy object. For example, we are more likely to notice that a drumbeat is loud if we have been listening to, say, a gentle violin. And we will notice that we are lifting extra pounds if they are added to a lightly packed suitcase. The same additional weight is barely noticeable in a heavy one. Vision, heat perception, smell and taste all obey a similar law: Perception is largely a relative mechanism.

Recent work in neuroeconomics suggests this link between dollars and senses is not just metaphorical. The economists Antonio Rangel of the California Institute of Technology and John A. Clithero of Pomona College say similar factors are at play in both cases.

This neurological connection is fascinating, a reminder that even higher order cognition has humble origins. But these kinds of errors aren’t inevitable. We may not be able to control how our senses manage stimuli, but we can control how we manage our money.