The popularity of Vermont’s Heady Topper beer is a classic example of persuasion’s scarcity principle at work: People are persuaded to act when an item is in short supply.

Heady Topper is a craft beer, sometimes called a microbrew, that is made and sold only in Vermont, and customers find it so irresistable that they drive hours to stand in line inside and outside stores awaiting the beer truck’s daily delivery. Customers often grab every six-pack off the cart the moment the driver wheels it inside the store door. The beer never reaches the cooler. (Read more in this Boston Globe story:

Psychologist Timothy Brock, who developed the “commodity theory,” said a product will be valued to the extent that it is unavailable. Social psychologist Robert Cialdini labeled this the scarcity principle.

The scarcity of something triggers three psychological processes, according to psychologist Anthony Pratkanis. Here’s what people are thinking:

  • If the availability of something shrinks, it must be valuable.
  • We feel a sense of urgency and psychological pressure to acquire the item that is in short supply. We saying to ourselves, I need to have that now.
  • When we have something that is scarce, we feel important, because no one else has what we have.

It is because of these processes that people are more likely to buy a piece of clothing if the sales person says there are only two left in the customer’s size, and our ears perk up when someone tells us that she is sharing information that no one else knows. If no one else has it, we want it.

Con artists use the scarcity principle to pitch gold coins to the elderly, telling them that there were thousands of the coins when they were minted in 1862 but that only four of them remain. The truth is there are thousands remaining, but swindlers will fabricate the rare nature of the coin “to build value in the mind of the victim,” Pratkanis says in his book Weapons of Fraud.

You can use the principle to your advantage in the workplace. If you are a training manager and you want to persuade people to sign up for a particular course, promote the fact that there is limited seating, and as the deadline for signing up approaches, announce that there are only three days remaining (or two days or one day) to enroll.