Final answer:
Jackie trains her dog to bring the mail by using shaping, a technique where successive steps toward a desired behavior are rewarded.
Step-by-step explanation:
When Jackie is giving her dog, Dodger, treats each time he goes to the mail slot as part of training to bring her the mail, this is an example of shaping. Shaping is a technique used in operant conditioning where successive approximations of a desired behavior are rewarded. Instead of expecting Dodger to understand and perform the complex task all at once, Jackie rewards him for smaller actions that lead up to the final goal, thereby shaping his behavior towards bringing the mail.