Operant Conditioning


Operant Behaviour
The Skinner Box
Three-term Contingency
Reinforcement, Punishment, and Extinction
Primary and Secondary Reinforcers
Superstitious Behaviour
Schedules of Reinforcement
Shaping and Chaining
Generalization and Discrimination

Operant Behaviour

Skinner was interested in behaviours that have effects on the environment, and on the behaviours themselves. Behaviours that act, or 'operate' on physical and social environments are called operants. Operant conditioning is changes in behaviours, such as an increase or decrease in the frequency of occurance, due to the consequences of these behaviours (Nye, 1992).
Charles Darwin 's notion of natural selection, Edward Thorndike 's 'Law of Effect', and Skinner's theory of operant learning are based on the same idea: If the consequence is favourable, the likelihood that the cause of the consequence will will occur, increases. (Lefrancois, 2000).

The Skinner Box

Skinner built a small soundproof chamber, called an operant chamber, to observe, manipulate, and record the behaviour of animals (Carlson & Buskist, 1997)

The Skinner Box

The environmental conditions in the box can be manipulated to observe how they affect the response rate of the animal.

A typical Skinner study involved the observation of rats pressing a lever, or pigeons pecking at at disk in an operant chamber, which would trigger a dispenser to release food. Skinner's main interest was not in the actual behaviour (pecking or pressing), but in the rate that these behaviours occur under different conditions. It is important to understand the conditions under which a behaviour increases or decreases because we base our assumptions about people's attributes on observations of the frequency of the occurance of certain behaviours (Nye, 1992).

Three-term Contingency

The three-term contingency is the relationship between the preceeding event ( discrimintative stimulus), the response (operant behaviour), and the following event (consequence) (Carlson & Buskist, 1997).

The following scenario is representative of the three-term contingency:

• You walk in the park and it starts raining.
• You open your umbrella and hold it over your head.
• You remain dry.

• The discriminitave stimulus is the rain.
• The operant behaviour is using the umbrella.
• The consequence is remaining dry.

Remaining dry is contingent on using the umbrella. The favourable outcome reinforces the behaviour. Thus, the likelihood of the behaviour occuring in future presence of the discrimimitave stimulus increases. You will not normally use an umbrella if it is not raining and even if you did it would have no effect: The operant behaviour will have no effect in the absence of the discriminitive stimulus (Calson & Buskist, 1997).

Reinforcement, Punishment, and Extinction

An operant response acts as a reinforcer if it produces a favourable consequence. There are two classes of reinforcers:

1. A positive reinforcer - The occurance of an appititive stimulus, following a response, that acts to increase the frequency of that response (Milhollan & Forisha, 1972).
   
   If a student gets praised for raising his or her hand in class, and the hand-raising increases in frequency, praise can be viewed as a positive reinforcer.
   
   
2. A negative reinforcer - The termination of an aversive stimulus, following a response, that acts to increase the frequency of that response (Milhollan & Forisha, 1972).
   
   If a person is hungry, eating will stop the hunger. Thus, feeling hungry is an aversive stimulus, and eating is a negative reinforcer.

Reinforcement, both positive and negative, results in an increase in behaviour (Carlson & Buskist, 1997).


An aversive stimulus, following a response, that acts to decrease the frequency of that response, is called a punisher .

If a child gets bitten after pulling a dog's tail, it would be likely that the tail-pulling behaviour will decrease in frequency. The bite is the punisher.

The use of punishment has several negative side effects including the risk of causing serious physical harm, inducing fear or hostility (the child might develop a fear of all dogs after being bitten), and the failure to learn the correct response in the particular situation (Carlson & Buskist, 1997).

The removal of an appititive stimulus is also a form of punishment. A well known example of this form of punishment, called response cost, is 'time out'. Removing a child from a stimulating activity serves as punishment for undesirable behaviour.


When a response is no longer followed by a reinforcer, this previously reinforced response decreases in frequency. This is called extinction . For example, a child will stop throwing tantrums if they are no longer reinforced by paying attention to them. This happens not because the child has forgotten how to kick and scream, but because such behaviour fails to produce the desired effect. Extinction is different from forgetting (Carlson & Buskist, 1997).

Primary and Secondary Reinforcers

Primary reinforcers, such as food, water, and extreme temperatures, are related to our basic biological functioning. Secondary, or conditioned, reinforcers are stimuli that are originally neutral, but become reinforcers through their association with primary reinforcers. A powerful secondary reinforcer is money. It has been paired with many primary reinforcers. Generalized reinforcers are secondary reinforcers paired with more that one primary reinforcer. Affection is an example of a generalized reinforcer. It has been paired with sexual contact, and obtaining resources such as warmth and protection (Nye, 1992).

Superstitious Behaviour

Accidental reinforcement of a response can lead to superstitious behaviour. Skinner demonstrated the conditioning of such behaviour using pigeons. He set the dispenser to deliver food to animals in an operant chamber at fixed time intervals, for example every 15 minutes. The pigeons associated whatever behaviour they were engaging in at the time of the food being dispensed with the delivery of the food. The likelihood of those behaviours occuring then increased. Skinner conditioned pigeons to spin around in circles, nod their heads, or to make swaying motions. (Nye, 1992)


Schedules of Reinforcement

Continious Reinforcement : Every response is reinforced. For example, every time a pigeon pecks at the disk in an operant chamber, food is dispensed.

Intermittent Reinforcement :

• Fixed ratio schedule: Reinforcement is delivered after a fixed number of responses has been made. For example, every fith time a pigeon pecks at the disk in an operant chamber, food is dispensed.
• Variable ration schedule: The number of responses required for a reinforcer to be delivered, varies for each trial. For example, a slot-machine requires a variable number of responses after each trial to pay-out.
• Fixed-interval schedule: A reinforcer is delivered after a fixed amount of time has elapsed. For example, food is dispensed at 15 minute intervals.
• Variable-interval schedule: A reinforcer is delivered after an average amount of time has elapsed. For example, food may be dispensed after 30 seconds on the first trail, and after 90 seconds on the second trial, but the average stays 60 seconds (Carlson & Buskist, 1997).
  

Schedules of reinforcement affect the rate of response, the acquisition of a behaviour, and resistance to extinction.
If continious reinforcement is used, as oposed to intermittent reinforcement, acquistion (learning) of the behaviour will occur faster. However, extinction of the learned behaviour will also occur faster upon termination of continious reinforment, as oposed to termination of intermittent reinforcement (Lefrancois, 2000).

Shaping and Chaining

Shaping involves reinforcing successive approximations of a desired behaviour. It is widely used by animal trainers to teach the animals to perform tricks.



Chaining involves one response leading to the occurance of another response. Most behaviours occur in chains. A basic example of chaining is saying the letters of the alphabet. The letter A acts as the discriminitive stimulus to produce the next response, saying the letter B, and so on (Milhollan & Forisha, 1972).

Generalization and Discrimination

Generalization involves the elicitation of a response to a stimulus that resembles the discriminitave stimulus. Generalization is useful in that it facilitates the transfer of behaviour across similar situations. For example, a secretary who can type on a typewriter can also type on a computer keyboard.

Discrimination involves the elicitation of a response only in the presence of a specific discriminative stimulus, and not in the presence of similar stimuli. Discrimination is useful when a particular response is not appropriate in similar situations. For example, behaviour that is appropriate in a fast-food restaurant, such as eating with your hands, may not be appropriate in a French restaurant. (Carlson & Buskist, 1997)