The Reciprocity Principle: Why Free Samples Are a Trap

This article is an excerpt from the Shortform summary of "Influence" by Robert B. Cialdini. Shortform has the world's best summaries of books you should be reading.

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When you take a free sample at the grocery store without buying something, do you feel a twinge of guilt? The Reciprocity Principle explains how getting something for “free” creates future obligations. We feel like we have to buy some cheese if we took a free cube because of the reciprocity principle of persuasion.

Learn about Cialdini’s Reciprocity Principle definition and understand how the principle of reciprocity came about.

What Is the Reciprocity Principle?

The Reciprocity Principle tells us to repay others when they do something for us. This fixed-action pattern of behavior is so deeply ingrained that we hardly think about it, yet we practice it all the time. When a friend treats you to lunch, you make sure you pick up the check the next time you go out; when your neighbors invite you to a party, you invite them the next time you’re hosting an event. 

That the phrase “much obliged” is a synonym for “thank you” is a powerful encapsulation of the Cialdini’s Reciprocity Principle of persuasion: we naturally feel obliged, indebted to those who have done something for us. By invoking reciprocity, persuasion is easier.

The principle of reciprocity can even extend beyond these small day-to-day courtesies to the world of international diplomacy. When Mexico City was devastated by an earthquake in 1985, Ethiopia dutifully made a foreign aid contribution to help the rebuilding and recovery effort. But why would a country like Ethiopia, poverty-stricken and suffering through a devastating famine, spend its scarce resources to help people all the way on the other side of the world? Simple: the Reciprocity Principle of persuasion. In 1935, when Ethiopia was invaded and occupied by the Italians, Mexico was one of the few countries to send aid. The Ethiopians were returning the favor, 50 years later.

The Origins of Reciprocity: Networks of Obligation

Why is the principle of reciprocity such an intuitive part of the human experience? Because evolution favored early human communities with strong social cohesion and an ability to work together.

The Reciprocity Principle was the glue that enabled social cohesion. If another individual brought you some firewood, for example, bringing them some of your own firewood would help the two of you survive and make the overall clan or tribe stronger.

This created networks of obligation among early humans that made it easier for the group as a whole to multiply and survive. In a harsh and unforgiving environment, like many prehistoric peoples faced, this was the only way to ensure group survival and prosperity.

It also lowered the cost of giving things up to one’s neighbors: you weren’t really losing something if you knew it would eventually come back to you. This is how humans came to rely on the principle so heavily. These networks of future obligations, in turn, enabled communities to divide labor, trade for scarce goods with their neighbors, create systems of mutual defense, and develop hierarchies and functional divisions within society. This inheritance from evolution is why we still adhere to the Reciprocity Principle today: we’re all taught that it’s bad to be a moocher or freeloader.

(Shortform note: The Reciprocity Principle became even more deeply ingrained as primitive communities grew into complex and interdependent societies. Looking at early Mesopotamia, for example, we see that large-scale, collective efforts like monument-building or the irrigation projects that enabled the Sumerians to control the flooding of the Tigris and Euphrates Rivers could have only been possible if there were some social mechanism that obliged people to assist one another in these endeavors.)

Gifts, Favors, and “Free” Samples: Exploiting the Reciprocity Principle

Unfortunately, the Reciprocity Principle also represents an evolutionary blind spot that compliance practitioners know how to exploit. They know that you’re more likely to feel obliged to them if they offer you some small gift or token gesture of kindness before they make their request. With reciprocity, persuasion follows.

Described by Robert Cialdini, reciprocity overpowers our other senses: you don’t even have to like the person making you the offer, you don’t need to have asked for it, nor do you have to desire the thing being offered to you for the principle to work its persuasive magic.

Without the sense of indebtedness, most people would never agree to the requests. The Reciprocity Principle is why sellers are so fond of promotional offers, free samples, and small gifts.

They know that by accepting these offers, you’ll become indebted to them: and their goal is to get you to fulfill your future obligation by purchasing their product. The best part for them is how subtle it is. They don’t have to directly ask you for anything, and they can never be accused of pressuring you into anything: all they did was offer you a free sample!  Blame the principle of reciprocity’s persuasion.

Of course, they know how hard it is for you to take a small piece of cheese, for example, without buying at least a little: they know how painful it is for you to feel like a moocher. Thus you comply with their request or abandon your ingrained sense of fairness and obligation.

The Reciprocity Principle: Why Free Samples Are a Trap

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Rina Shah

An avid reader for as long as she can remember, Rina’s love for books began with The Boxcar Children. Her penchant for always having a book nearby has never faded, though her reading tastes have since evolved. Rina reads around 100 books every year, with a fairly even split between fiction and non-fiction. Her favorite genres are memoirs, public health, and locked room mysteries. As an attorney, Rina can’t help analyzing and deconstructing arguments in any book she reads.

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