What reinforcement behavior is reinforced some but not all the time?

Intermittent schedules of reinforcement (INT) are when some, but not all, instances of a behavior are reinforced. An intermittent schedule of reinforcement can be described as either being a ratio or interval schedule. A variable schedule is when the number or time between reinforcements changes according to an average. This is in contrast to continuous reinforcement which provides a reinforcement each and every time a behavior is emitted. With continuous reinforcement, if every time you hear the doorbell ring and there is someone on the other side of the door with a package for you, that would be continuous reinforcement. Intermittent schedules of reinforcement are different from this and from extinction, where a previously reinforced behavior is no longer reinforced at all. All reinforcement is withdrawn with a schedule of extinction. Intermittent reinforcement can take the form of fixed or variable ratio or interval schedules, with the variable schedule being when the number or time between reinforcements changes. A fixed schedule is when the number of responses or the amount of time remains constant.