Researchers have found that when something is hard to get, people want it more. This observation is often manipulated by groups and people who want to sell something. They imply that a product is in scarce supply, even when it is not, in order to increase demand for it.
Example: A grocery store advertises a brand of yogurt for a reduced price, noting in the ad that there is a limited supply.
People often try to change others’ attitudes through persuasion. There are four elements involved in persuasion: the source, the receiver, the message, and the channel.
The person who sends a communication is called the source. Persuasion is most successful when a source is both likable and credible. Credible sources are those that are trustworthy or that have expertise.
An expert source is particularly likely to increase persuasion when a communication is ambiguous.
Sources are considered less trustworthy if they seem to have a vested interest in persuading people. On the other hand, sources seem more trustworthy if they provide counterarguments for their position.