Yes. Across more than two decades of studies, people consistently spend more when they pay by card than when they pay with cash. In one landmark MIT experiment, participants were willing to pay up to around 100% more for the same item when using a credit card instead of cash. The exact size of the effect varies by study and situation, but the direction almost never does: plastic loosens the wallet.

What the research actually found

The most cited study is Prelec and Simester's "Always Leave Home Without It" (MIT, 2001). In sealed-bid auctions for tickets, participants who could pay by credit card bid dramatically more than those paying cash — by margins reported in the range of roughly 60% to over 100%. The researchers concluded that credit cards effectively "step on the gas" for spending. (MIT Sloan summary)

It is not a one-off finding. Earlier work by Feinberg (1986) showed that the mere presence of credit card logos increased spending in lab settings. Later field and lab studies — including work by Soman, and by Runnemark, Hedman, and Xiao (2015) — found people report a higher willingness to pay with cards than cash. More recent neuroscience from MIT Sloan even found that card payments activate the brain's reward network more strongly than cash.

Why it happens: the "pain of paying"

Behavioral economists have a name for the mechanism: the pain of paying. Handing over physical cash creates a small, real moment of loss — you watch the money leave. A card decouples the purchase from the payment: you get the item now, and the "cost" is an abstract number that clears later. Less felt pain in the moment means less friction, and less friction means more spending.

Two forces stack on top of each other:

Decoupling. Card and especially contactless or mobile payments separate the pleasure of buying from the discomfort of paying, so the brake barely engages.
Lower salience. Cash is a running tally you can literally see thinning in your wallet. A card balance is invisible until the statement arrives.

How big is the effect, honestly

It is worth being precise, because the "100% more" figure gets thrown around loosely. That number came from a specific auction experiment, not your weekly groceries. Everyday effects are usually smaller and vary a lot by category, amount, and person, and a few studies find weaker or mixed results. The honest summary is this: the direction of the finding is remarkably robust — people tend to spend more with cards — while the magnitude depends heavily on context. You should not expect to halve your spending by switching to cash, but the nudge is real and worth using.

What to do about it

You do not have to go cash-only to benefit from this. The useful takeaway is to put the "pain of paying" back into card spending on purpose.

Add a moment of friction. Log the purchase the instant you tap. The two seconds it takes to record an expense recreates a little of the awareness cash gives you for free — this is the whole idea behind conscious spending.
Use cash for problem categories. If dining out or impulse buys are where you leak, paying those in cash reintroduces the brake exactly where you need it.
Make the invisible visible. Since a card hides your running total, a tracker that shows the total as it climbs restores the wallet-thinning signal. That is also why Apple Pay can quietly increase spending unless you track it.

How Lumi helps

The research points to a simple fix: bring back awareness at the moment of payment. Lumi is built for exactly that. Logging a card or Apple Pay purchase takes about two seconds with Back Tap, or imports automatically, so you get the small moment of friction that cash provides without giving up the convenience of cards. You see each category's total climb in real time — the wallet-thinning signal a card normally hides — and an AI month-end forecast flags trouble early. No bank login, and your data stays on your device.

Ready to take control of your spending?

Download Free on App Store

Frequently asked questions

How much more do people spend with a card than cash?

It depends on the study and situation. A famous MIT auction experiment found willingness to pay up to roughly 100% higher with a credit card, but everyday effects are usually smaller. What is consistent is the direction: people tend to spend more with cards than cash.

Does this apply to debit cards and Apple Pay too?

The core mechanism — the reduced "pain of paying" from not handing over physical cash — applies to debit, contactless, and mobile payments as well. Some research suggests the more frictionless the payment, the weaker the mental brake.

Should I switch to cash to spend less?

You do not have to. Many people get most of the benefit by keeping cards for convenience and adding awareness back in: logging each purchase, or using cash only for the categories where they tend to overspend.

Why does cash feel different?

Because you physically see and part with it. That visible loss is the "pain of paying," and it acts as a natural brake that abstract card balances remove.

The takeaway

The evidence is clear enough to act on: paying by card tends to increase spending because it removes the small, useful pain of parting with money. You can get that brake back without giving up your cards — by making each purchase visible the moment it happens.

This is general information, not financial advice.