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Operant Conditioning

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Types of Intermittent Reinforcement Schedules

There are four main types of intermittent schedules, which fall into two categories: ratio or interval. In a ratio schedule, reinforcement happens after a certain number of responses. In an interval schedule, reinforcement happens after a particular time interval.

  • In a fixed-ratio schedule, reinforcement happens after a set number of responses, such as when a car salesman earns a bonus after every three cars he sells.
  • In a variable-ratio schedule, reinforcement happens after a particular average number of responses. For example, a person trying to win a game by getting heads on a coin toss gets heads every two times, on average, that she tosses a penny. Sometimes she may toss a penny just once and get heads, but other times she may have to toss the penny two, three, four, or more times before getting heads.
  • In a fixed-interval schedule, reinforcement happens after a set amount of time, such as when an attorney at a law firm gets a bonus once a year.
  • In a variable-interval schedule, reinforcement happens after a particular average amount of time. For example, a boss who wants to keep her employees working productively might walk by their workstations and check on them periodically, usually about once a day, but sometimes twice a day, or some-times every other day. If an employee is slacking off, she reprimands him. Since the employees know there is a variable interval between their boss’s appearances, they must stay on task to avoid a reprimand.
Response Patterns

These different types of reinforcement schedules result in different patterns of responses:

  • Partial or intermittent schedules of reinforcement result in responses that resist extinction better than responses resulting from continuous reinforcement. Psychologists call this resistance to extinction the partial reinforcement effect.
  • Response rate is faster in ratio schedules than in interval schedules. Ratio schedules depend on number of responses, so the faster the subject responds, the more quickly reinforcement happens.
  • A fixed-interval schedule tends to result in a scalloped response pattern, which means that responses are slow in the beginning of the interval and faster just before reinforcement happens. If people know when reinforcement will occur, they will respond more at that time and less at other times.
  • Variable schedules result in steadier response rates than fixed schedules because reinforcement is less predictable. Responses to variable schedules also cannot be extinguished easily.


As in classical conditioning, extinction in operant conditioning is the gradual disappearance of a response when it stops being reinforced. In the earlier example, Lisa’s dog, Rover, started to put the remote under her chair regularly because she continuously reinforced the behavior with pats on his head. If she decides that the game has gone too far and stops patting him when he does it, he’ll eventually stop the behavior. The response will be extinguished.

Stimulus Discrimination

If Lisa enjoys Rover’s antics with the TV remote only in the daytime and not at night when she feels tired, Rover will put the remote under her chair only during the day, because daylight has become a signal that tells Rover his behavior will be reinforced. Daylight has become a discriminative stimulus. A discriminative stimulus is a cue that indicates the kind of consequence that’s likely to occur after a response. In operant conditioning, stimulus discrimination is the tendency for a response to happen only when a particular stimulus is present.

Stimulus Generalization

Suppose Lisa’s dog, Rover, began to put the remote under her chair not only during the day but also whenever a bright light was on at night, thinking she would probably pat him. This is called stimulus generalization. In operant conditioning, stimulus generalization is the tendency to respond to a new stimulus as if it is the original discriminative stimulus.