Final answer:
Lance is being rewarded on a variable ratio reinforcement schedule, where the number of responses needed for a reward varies.
Step-by-step explanation:
Lance is being rewarded on a variable ratio reinforcement schedule.
In a variable ratio schedule, the number of responses needed for a reward varies. This type of schedule is commonly seen in situations where the timing or quantity of the desired behavior is unpredictable. For example, in Lance's case, he sells one policy for every three houses on some days and one policy for every twenty houses on other days.
Keywords: variable ratio, reinforcement schedule, unpredictable, timing, quantity