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.
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.
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.
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.