How Businesses Use Psychology to Manipulate You

Most of the decisions you make as a customer were designed before you walked in.

The size of the popcorn. The tempo of the music. The order of the menu. The size of the basket someone hands you at the door. None of it is an accident, and almost none of it is illegal. It is just applied psychology, and businesses have been running these experiments on you for decades.

In the video I covered four of them. A lot of you asked for the full guide, so here it is. A quick recap of the four, then the ten more I promised.

The four from the video

The decoy effect. The medium popcorn is priced suspiciously close to the large so the large looks like an obvious deal. The medium exists to be rejected. Dan Ariely made this famous with The Economist’s subscription page: a print-only option nobody chose, which existed only to make print-plus-web look like a bargain.

Music tempo. Research going back to Milliman in the 1980s found that slower background music makes shoppers move slower and diners linger longer, and faster music does the opposite. Lunch spots that need turnover play fast. Bars play fast so you drink faster. The upscale place plays slow so you order the second glass of wine.

Price anchoring. The $150 steak on the menu is not there to be ordered. It is there to make the $60 steak feel reasonable. Once a high number enters your head, everything below it looks cheaper than it is. This works in retail, software pricing pages, and every “compare plans” table you have ever seen.

Basket size. Grocery chains have been enlarging carts for years because bigger carts reliably increase spend. Sephora hands you a basket even though every product fits in one hand. The empty space is a suggestion.

Now the rest.

1. Charm pricing

$9.99 is not $10. Not to your brain.

We read numbers left to right and give the first digit far more weight than it deserves. Thomas and Morwitz (2005) called it the left-digit effect: dropping a price by one cent from $10.00 to $9.99 changes how the price is encoded, while dropping from $9.60 to $9.59 does almost nothing. The effect is biggest when the left digit changes.

Spot it: almost every price ending in 9, 95, or 99.

Defend: round up before you compare. $9.99 is ten dollars. $499 is five hundred.

2. Scarcity and urgency

“Only 3 left in stock.” “Sale ends at midnight.” “12 people are looking at this right now.”

Scarcity makes things feel more valuable and makes deciding feel more urgent. In a classic experiment, Worchel, Lee and Adewole (1975) had people rate cookies from a jar. The same cookies were rated as more desirable when there were two in the jar than when there were ten, and more desirable still when the jar started full and was then depleted in front of them.

Booking sites, fast fashion, and every countdown timer on a checkout page are running this play. Some of those counters are real. Many are on a loop.

Spot it: any message that tells you supply is low or time is short.

Defend: ask whether the scarcity is real. If you cannot verify it, treat it as decoration. And if it is real and you still do not need it, you have lost nothing.

“Bestseller.” “Most popular.” “4.8 stars from 12,000 reviews.” “Chef’s recommendation.”

When we are unsure, we copy what other people do. Robert Cialdini spent a career documenting this. Goldstein, Cialdini and Griskevicius (2008) tested hotel signs asking guests to reuse towels. A standard environmental appeal got a 35 percent reuse rate. Telling guests that most other guests in this room reused their towels pushed it to 49 percent.

A “most popular” badge on a pricing page is the same mechanism. So is the menu item with a little box around it. So is the “customers also bought” row.

Spot it: any claim about what other people chose.

Defend: popularity tells you what sold, not what is right for you. Check whether the “most popular” plan is also the one with the highest margin. It usually is.

4. Defaults

Whatever is pre-selected is what most people end up with.

Johnson and Goldstein (2003) compared organ donor rates across European countries. Countries where you had to opt in sat between 4 and 28 percent. Countries where you had to opt out sat above 85 percent. Same humans, same decision, different default.

Businesses know this. The subscription auto-renews. The newsletter checkbox is pre-ticked. The upgrade is selected. The “add protection plan” is toggled on. Changing the default costs a click, and most people never click.

Spot it: anything already selected, checked, or toggled when you arrive.

Defend: before you pay, read every pre-filled choice as if it were blank. Uncheck first, then decide.

5. Endowed progress

The coffee shop punch card with two stamps already on it.

Nunes and Drèze (2006) tested this at a car wash. One group got a card requiring 8 washes for a free one. Another got a card requiring 10, but with 2 stamps already punched. Same 8 washes to go. The pre-stamped group completed the card at nearly twice the rate, and did it faster.

Once you feel you have started something, you want to finish it. Loyalty apps, profile completion bars, and “you’re 40 percent of the way to free shipping” are all endowed progress.

Spot it: any progress you did not earn.

Defend: ask what it costs to finish. If you would not buy the tenth coffee without the card, the card is buying it for you, with your money.

6. Reciprocity

The free sample. The mint with the bill. The free trial that asks nothing up front.

Being given something creates a small pressure to give back. Strohmetz and colleagues (2002) had servers deliver a mint with the check. One mint raised tips about 3 percent. Two mints raised them about 14 percent. When the server gave one mint, walked away, then came back and gave a second “just for you,” tips rose about 23 percent.

Costco’s sample stations are not generosity. Neither is the free consultation, the free audit, or the free chapter.

Spot it: anything free that arrives before you have decided.

Defend: take the free thing. Say thank you. Then decide as if you had paid for it, because you may be about to.

7. Dropping the dollar sign

Look at a menu in a nice restaurant. The prices say “28,” not “$28.00.”

Yang, Kimes and Sessarego (2009) at Cornell tested menu price formats in a real restaurant. Guests who saw numerals with no dollar sign spent significantly more than guests who saw the same prices with dollar signs. The symbol reminds you that money is leaving. Remove it and the number becomes a little less real.

The same logic drives casinos moving you from cash to chips, apps selling “gems” and “coins,” and any interface that shows a number without the currency attached.

Spot it: prices with no currency symbol, or spending measured in points, credits, or tokens.

Defend: convert back to dollars out loud. 28 is twenty-eight dollars. 500 gems is whatever you paid for them.

8. Choice architecture and the paradox of choice

The famous version is Iyengar and Lepper (2000): a grocery store tasting table with 24 jams versus 6. The big table drew more people, but the small table sold about ten times as many jars.

Businesses learned two things from this. First, a shorter menu can convert better than a long one. Second, when a big menu is unavoidable, you can steer people through it with a highlighted “recommended” option, a boxed item, or a “start here” tier.

One honest caveat. A 2010 meta-analysis by Scheibehenne, Greifeneder and Todd found that across many studies the average effect of choice overload is close to zero. It shows up under some conditions and vanishes under others. The steering tactics are real and widely used. The idea that fewer choices always sell more is not.

Spot it: the pre-highlighted option in a wall of options.

Defend: ignore the highlight and read the row you were not meant to read. The cheapest plan is usually the one at the far end, rendered in the smallest type.

9. Store layout

Milk is at the back of the store because you came for milk, and the walk takes you past everything else.

Products at eye level sell more. Chandon and colleagues (2009) used eye tracking in a real shelf setting and found that placement and the number of facings strongly influenced attention and choice. Brands pay slotting fees for those shelf positions, and store-brand items are placed exactly where they will be seen next to the premium name.

Paco Underhill’s decades of in-store observation added more: most shoppers turn right on entering, slow down after a few steps, and avoid narrow aisles. Stores are built around those habits. The impulse items sit where you wait, and the sale bins sit where you slow.

Spot it: the walk you have to take to reach what you came for.

Defend: shop from a list. Look at the top and bottom shelves, where the cheaper versions usually are. And do not decide anything in the checkout line.

10. The endowment effect and the free trial

We value things more once we own them.

Kahneman, Knetsch and Thaler (1990) gave half a room of students a coffee mug and asked what they would sell it for. The other half was asked what they would pay for one. Sellers wanted roughly twice what buyers would pay. Nothing about the mug changed. Ownership did.

This is why the free trial works even when the product is average. Thirty days in, cancelling feels like losing something rather than declining something. It is why “try it at home for 100 nights” mattresses exist. It is why you can put the car in your driveway for a weekend.

Spot it: any offer that puts the product in your hands before you have paid for it.

Defend: set a calendar reminder for the day before the trial ends, and write down on day one what the product would have to do to be worth it. Judge day thirty against day one, not against the feeling of giving it up.

The pattern behind all fourteen

Every one of these works on the gap between how you think you decide and how you actually decide.

You think you compare prices. You actually compare the price to the number next to it. You think you choose what you want. You actually take the default. You think you are immune to a countdown timer. You are not, and neither am I.

None of this makes the businesses evil. Most of these tactics are standard practice and many are genuinely useful when the product is good. But you should know the moves. Once you can name a tactic, it loses most of its power.

So next time you are standing in front of the popcorn, name it. Then buy whatever size you actually want.

Sources

Ariely, D. (2008). Predictably Irrational. HarperCollins.
Chandon, P., Hutchinson, J. W., Bradlow, E. T., & Young, S. H. (2009). Does in-store marketing work? Effects of the number and position of shelf facings on brand attention and evaluation at the point of purchase. Journal of Marketing, 73(6), 1–17.
Cialdini, R. B. (2006). Influence: The Psychology of Persuasion. Harper Business.
Goldstein, N. J., Cialdini, R. B., & Griskevicius, V. (2008). A room with a viewpoint: Using social norms to motivate environmental conservation in hotels. Journal of Consumer Research, 35(3), 472–482.
Iyengar, S. S., & Lepper, M. R. (2000). When choice is demotivating: Can one desire too much of a good thing? Journal of Personality and Social Psychology, 79(6), 995–1006.
Johnson, E. J., & Goldstein, D. (2003). Do defaults save lives? Science, 302(5649), 1338–1339.
Kahneman, D., Knetsch, J. L., & Thaler, R. H. (1990). Experimental tests of the endowment effect and the Coase theorem. Journal of Political Economy, 98(6), 1325–1348.
Milliman, R. E. (1982). Using background music to affect the behavior of supermarket shoppers. Journal of Marketing, 46(3), 86–91.
Milliman, R. E. (1986). The influence of background music on the behavior of restaurant patrons. Journal of Consumer Research, 13(2), 286–289.
Nunes, J. C., & Drèze, X. (2006). The endowed progress effect: How artificial advancement increases effort. Journal of Consumer Research, 32(4), 504–512.
Scheibehenne, B., Greifeneder, R., & Todd, P. M. (2010). Can there ever be too many options? A meta-analytic review of choice overload. Journal of Consumer Research, 37(3), 409–425.
Strohmetz, D. B., Rind, B., Fisher, R., & Lynn, M. (2002). Sweetening the till: The use of candy to increase restaurant tipping. Journal of Applied Social Psychology, 32(2), 300–309.
Thomas, M., & Morwitz, V. (2005). Penny wise and pound foolish: The left-digit effect in price cognition. Journal of Consumer Research, 32(1), 54–64.
Underhill, P. (1999). Why We Buy: The Science of Shopping. Simon & Schuster.
Worchel, S., Lee, J., & Adewole, A. (1975). Effects of supply and demand on ratings of object value. Journal of Personality and Social Psychology, 32(5), 906–914.
Yang, S. S., Kimes, S. E., & Sessarego, M. M. (2009). $ or dollars: Effects of menu-price formats on restaurant checks. Cornell Hospitality Report, 9(8).