1) A compound schedule in which two or more component schedules opera te in alternation, all during the same stimulus. Occasionally, a VI or VR schedule with a limited number of schedule values is referred to as a mixed schedule (e.g., a VR schedule arranged by randomly alternating between FR 10 and FR 20 may be called mixed FR 10 FR 20).

2) Reinforcement is programmed by two or more schedules alternating usually at random. No stimuli are correlated with the schedules as in multiple schedules. (E.g., mix FI 5 FR 50 represents a schedule in which a reinforcement sometimes occurs after an interval of 5 minutes and sometimes after a "ratio" of 50 responses, the possibilities occurring either at random or according to a program in any determined proportion.)