Cognitive fluency is the human tendency to prefer things that are familiar and easy to understand.

For marketers this means that the easier to understand your offer is, the more likely people are to buy it.

Psychologists have determined, for example, that shares in companies with easy-to-pronounce names do indeed significantly outperform those with hard-to-pronounce names. Coincidence? Nope.

Example: people prefer unlimited plans

Understanding and comparing different cell phone plans is a pain and takes too much time. Who wants to spend minutes comparing monthly minutes and text-message limits? So what do people do? They go with the unlimited plan. It's often not the best value, but it's easy to understand.

Cell phone companies make the most money from unlimited plans, and they have an extra incentive to make other plans confusing. Plans with a fixed amount of minutes charge high fees for going over your allotted minutes - it's designed to cause you enough pain that you will switch to a plan with a higher regular fee.

Suggestion: make your offer and pricing as easy to understand as possible.