Random or variable reinforcement is a useful procedure in making a given behavior resistant to extinction, for example in the shaping process, when one wants to raise criteria. To go from reinforcing every response to selectively reinforcing stronger responses you need to develop enough resistance to extinction so that the animal neither changes the behavior instantly upon going unreinforced once or twice, nor quits altogether. Resistance to extinction is also important in maintaining long duration behaviors, as in searches, field trialing, and so on; and can be developed gradually. Bob and Marian Bailey might consider this simply another example of a shaping schedule.
