Final answer:
Frequent flyer miles are an example of a variable ratio reinforcement schedule, where the number of responses needed for a reward varies.
Step-by-step explanation:
Frequent flyer miles are an example of a variable ratio (VR) reinforcement schedule. In a VR schedule, the number of responses required for a reward varies. This is often used to maintain high and steady response rates, as seen in behaviors like gambling. The unpredictable nature of the VR schedule makes it particularly powerful in reinforcing behavior.