Final answer:
Scanning the night sky for unpredictable appearances of meteors or comets represents a variable interval reinforcement schedule, where the reinforcement comes at varying, unpredictable time intervals.
Step-by-step explanation:
Scanning the night sky for meteors or comets that appear at unpredictable times is an example of a variable interval reinforcement schedule. In this type of schedule, reinforcements (in this case, the appearance of meteors or comets) are given after varying and unpredictable intervals of time have passed. Just like Manuel in the fast-food restaurant example who never knows when the quality control person will show up but maintains a consistently clean and efficient operation, sky-watchers maintain a consistent level of vigilance because they can't predict when they'll be rewarded with a sighting.