Discriminative responding on associated mixed and multiple schedules as a function of food and ICS reinforcement.

Performance on associated mixed and multiple variable-interval-extinction schedules was studied as a function of food versus intracranial stimulation (ICS) reinforcement. For the mixed schedule, differential responding was greater for an ICS reinforcement group than for a food reinforcement group, demonstrating that conditions affecting resistance to extinction help to determine the control exerted by a mixed schedule. Performance on the multiple schedule demonstrated greater differential responding for an ICS group than for a food reinforcement group during the early training sessions, indicating that the control exerted by mixed schedules interacts with that exerted by the exteroceptive discriminative stimuli. The results suggest that the influence of the associated mixed schedule on discriminative responding would be greater, the greater the difficulty of the stimulus discrimination.