Shopping is war.

The battle is not just among the jostling crowds at the sale bins and cash registers in these pre-Christmas days; it is also between warring factions of our own brains, some economists and neuroscientists say.

Recent studies suggest that each buying decision plays out in the brain as a fight between a pleasure center seeking the bliss of acquisition and an aversion center seeking to avoid the pain of paying.

In the hot field of neuroeconomics, MRI scans have turned up heightened activity in deep, primitive areas of the brain as subjects shop. The nucleus accumbens, a seat of pleasure, lights up when they are contemplating a purchase, and the insula, a seat of disgust and pain, lights upwhen they are thinking about how much that purchase is going to cost.

As such findings accumulate, they suggest potential strategies for spending less – or at least, more wisely – at this difficult juncture of dark economy and season of light.

“Your purchasing decisions are largely emotional, driven by very inarticulate feelings you have, this pain-versus-pleasure tug of war,” said Jonah Lehrer, author of the forthcoming book, “How We Decide.”

“So it’s very important to impose a little bit of deliberation onto that emotional process, force yourself to think long-term, and rationally think through the consequences of what is ultimately a very emotional decision,” he added.

How might that be done?

Cash is best: First and foremost, researchers say, if you want to spend smarter, avoid using your credit card.

“One of the pernicious qualities of credit cards is that they anesthetize the pain of paying, which is ordinarily your first defense against overspending,” said George Loewenstein, professor of economics and psychology at Carnegie Mellon University.

Need convincing? In a 2001 study, two professors at MIT’s Sloan School of Management held an auction for tickets to a sold-out Celtics game, and divided subjects into those who must pay cash within 24 hours and those who must pay with credit cards. The credit-card buyers were willing to bid on average up to twice as much as the cash buyers, they found.

Know your feelings: Be aware that emotions that do not penetrate conscious awareness, and that have little to do with an actual buying decision, may still affect it. One study found that shoppers tended to spend much more when they were feeling down. Another found that men who had just been exposed to erotic pictures were more willing to take economic risks, and the trick seemed to be that the erotica set the nucleus accumbens, the pleasure center, on a roll.

“The idea is that if you can just change activation in these areas, no matter what the stimulus is, you might be able to push around financial decision-making,” said Brian Knutson, an associate professor of psychology and neuroscience at Stanford.

So how can you fight back against your unconscious emotions? Perhaps shop with a buddy who can supply reality checks, Knutson said. Others suggest shopping with a list and vowing not to deviate from it.

To avoid the stimulating atmosphere of stores, you might want to shop online. But that also has its dangers. “I would say one-click shopping on the Internet is a lot more dangerous than paying cash at the store,” Loewenstein said. “You can do a lot of damage in a short time.”

Lehrer also advises staying away from the free treats offered at Costco, Whole Foods, and elsewhere. As they activate the pleasure center, “they put you in the reward mood” for buying, said Lehrer.

Keep your distance: Avoid flirting with items you cannot afford, trying them on or carrying them around until they start to feel like yours, to avert what neuro-economists call “the endowment effect.”

Knutson explains it like this: In his classes, he’ll give a student a coffee mug, then ask how much he must pay to get the student to part with it. They usually reply that they’ll sell it for $4 to $6. But if he asks the other students how much they’d pay for such a mug, they usually price it at $2 or $3. Though it makes no economic sense, we tend to value things more highly simply because they’re ours. In a recent study, Knutson noted, brain scans bore out the phenomenon: the insula, the pain center, tended to kick in when subjects contemplated selling items they viewed as theirs.

Keep moving: Some researchers warn against buying too much in one store. “You may experience something called `decreasing sensitivity to losses,”‘ said Loewenstein. “Especially if you’ve spent a large amount, say $100, at a store, you don’t want to start buying a bunch of small stuff, because it will start feeling free. If you go to another store, it won’t feel free.”

Tightwads, in particular, need to watch out for this, he said, because they are prone to spending binges when they finally loosen their pursestrings.

Beware of bargains: As with credit cards, studies have found that the feeling of getting a bargain blunts the pain of payment. Call it the “You can’t go wrong at this price” effect. The insula lights up when people pay a price that seems high, and shuts down when they think they are getting a good deal, Loewenstein said: “That can interfere with rational decision-making just as much as the excitement about the good itself.”

Know why we buy: We give presents to foster social bonds, points out Dan Ariely, professor of behavioral economics at Duke and author of the recent book Predictably Irrational – and realizing that can help us refocus how we spend. Ariely says he tries to buy gifts that people wouldn’t have bought for themselves, either because they would feel too decadent or because they lacked knowledge about the item.

Get over the idea that it’s about money, Ariely said, and “You might be able to spend much less and get much more meaning out of it.”