Final answer:
Julie uses a variable ratio reinforcement schedule to train her dog, where treats are given after an unpredictable number of sits, averaging out to every seven times.
Step-by-step explanation:
Julie is using a variable ratio reinforcement schedule while training her dog to sit. In this type of schedule, the reinforcement, which in this case is treats, is given after an unpredictable number of responses (the dog's sitting behavior). For instance, Julie might give her dog a treat after the fifth sit, then after the ninth, then the sixth, and so on. The number of sits before a treat is given averages out to every seven times, but it varies from one reinforcement to the next, making it a variable schedule. This type of reinforcement schedule is known to produce a high and steady rate of response because the reward is unpredictable, similar to how slot machines operate, rewarding players after an undetermined number of plays.