Introduction to Reinforcement Schedules
A schedule of reinforcement is a tactic used in operant conditioning that influences how an operant response is learned and maintained. Each type of schedule imposes a rule or program that attempts to determine how and when a desired behavior occurs. Behaviors are encouraged through the use of reinforcers, discouraged through the use of punishments, and rendered extinct by the removal of a stimulus altogether. Schedules vary from simple ratio and interval-based schedules to more complicated compound schedules that combine one or more simple strategies to manipulate behavior.
Principles of Reinforcement Schedules
Learning in the real world does not necessarily follow a linear or rational pattern. By changing the schedule of reinforcement in experimentation, we can attempt to mimic how learning occurs naturally. Reinforcement can be used intermittently so that certain responses or behaviors are reinforced, and others are not. In experiments, when environments are controlled, behaviors become predictable, and specific variations of intermittent reinforcement can reliably induce specific patterns of responses.
Types of Schedules
Continuous schedules reward a behavior after every performance of the desired behavior. Simple intermittent reinforcement schedules, on the other hand, only reward the behavior after certain ratios or intervals of responsesRatio schedules enact an amount of reinforcement that is proportionate to the number of responses, such that a larger number of responses overtime will receive a larger amount of reinforcement. Interval schedules use a given time period during which the subject is reinforced only once, regardless of the amount of additional responses from the subject. Simple schedules can be either fixed or variable, meaning that the ratio or interval is either set at the outset or varies over time.
Fixed ratio schedules respond to a specific set ratio. In humans, fixed ratio reinforcement is used in payment for work such as fruit picking. Pickers are paid a certain amount (reinforcement) based on the amount they pick (behavior), which encourages them to pick faster in order to make more money.
Variable ratio schedules use a specific proportion but do not guarantee reinforcement in the same set pattern as in fixed ratio schedules. In humans, variable ratio reinforcement is used by casinos to attract gamblers. A slot machine pays out an average win ratio, say five to one, but does not guarantee that every fifth bet (behavior) will be rewarded (reinforcement) with a win.
Fixed interval schedules use a set time period, during which only one response will be reinforced. As opposed to the fixed ratio example above, fixed interval schedules exist in human payment systems when someone is paid hourly. No matter how much work that person does in one hour (behavior), they will be paid the same amount (reinforcement).
Variable interval schedules allow the time period to fluctuate, but maintain an average length of time used for reinforcement. People who like to fish experience the reinforcement of a variable interval schedule. On average, in the same location, a fisherman will catch about the same number of fish in a given time period. However, the fisherman does not know how or when those catches will occur (reinforcement) within the time period spent fishing (behavior).
All of these schedules have different advantages (Figure 1). In general, ratio schedules consistently elicit higher response rates than interval schedules because of their predictability. Variable schedules are categorically less-predictable so they tend to resist extinction and encourage continued behavior. Both gamblers and fishermen alike can understand the feeling that one more pull on the slot machine, or one more hour on the lake, will somehow change their luck and elicit their respective rewards. Thus, they continue to gamble and fish, regardless of previously unsuccessful feedback.
Compound schedules combine at least two simple schedules, and use the same reinforcer for the same behavior. Superimposed schedules use at least two simple schedules simultaneously. Concurrent schedules provide two possible simple schedules simultaneously, but allow the participant to respond on either schedule at will. All combinations and kinds of reinforcement schedules are intended to elicit a specific target behavior.