In the digital age, more information is available to more people than ever before. But not all the information. Truly unique and rare information — a hot stock tip, for instance, or a warning of an impending market shift — remains a near-priceless commodity. Smart businesspeople want the inside edge, and they’re willing to pay to get it. In the final installment of a six-part series on the science of persuasion, psychology and marketing Professor Robert Cialdini discusses how the principle of "scarcity" can be leveraged to convince people to buy into our suggestions, heed our advice or accept our business proposals.

People trust experts. In courtrooms, expert witnesses sway the views of jurors. On television, expert analysts shape public opinion on everything from politics to sports. And in the real world, people give their trust — and their money — to experts every day, says psychology and marketing Professor Robert Cialdini. In the fifth of a six-part series, Cialdini discusses the principle of "authority" — one of the six basic principles of persuasion.

Nobody likes being known as a liar or as wishy-washy or erratic. So, when people make public commitments or promises, they will almost always want to back up those words with action. They have little choice: For reputation’s sake, they must do so. In the world of psychology, this is a principle known as "consistency," and according to Robert Cialdini, it’s one of the six key principles behind the science of persuasion.