Thursday, March 15, 2012

Types Of Reinforcement

Operant Conditioning is the term used by B.F. Skinner to describe the effects of the consequences of a particular behavior on the future occurrence of that behavior. There arefour types of Operant Conditioning: Positive Reinforcement, Negative Reinforcement, Punishment, and Extinction. Both Positive and Negative Reinforcement strengthen behavior while both Punishment and Extinction weaken behavior.

Positive Reinforcement
In Positive Reinforcement a particular behaviour is strengthened by the consequence of experiencing a positive condition. For example, a hungry rat presses the lever in its cage and receives food. The food is a positive condition for the hungry rat. The rat presses the bar again and receives food. The rat's behaviour of pressing the lever is strengthened by the consequence of receiving food.

Skinner defined reinforcement as any operant that increases the rate of a response. An operant conditioning contingency that leads to reinforcement is : if the rat responds (presses the lever), then food is presented. The rate of response increases. This procedure is called positive reinforcement. The word "positive" is used because the consequence is the presentation of food. The word "reinforcement" is used since the effect of the contingency is to increase the rate of response. In most examples "positive reinforcement" is recognizable as a form of reward.

Negative Reinforcement
In Negative Reinforcement a particular behaviour is strengthed by the consequence of stopping or avoiding a negative condition. For example, a rat is placed in a cage and immediately receives a mild electrical shock on its feet. The shock is a negative condition for the rat. The rat presses a lever and the shock stops. The rat receives another shock, presses the lever again, and again the shock stops. The rat's behaviour of pressing the lever is strengthened by the consequence of stopping the shock.

The word "negative" is used because the consequence is the removal of shock. The word "reinforcement" is used since the effect of the contingency is to increase the rate of response.

This kind of negative reinforcement is also called escape. A similar procedure called avoidanceoccurs when the lever pressing allows the animal to totally avoid shock.

One can train an animal by positive reinforcement by waiting for the desired response and immediately rewarding the animal. Shaping is a process that speeds up the training process.To shape the animal's behaviour, the experimenter reinforces the animal for more and more specific steps in the desired behaviour. For example, a dog can be trained to roll over first by learning to lie down, then to lie down and roll onto one side, and ultimately to lie down, roll onto one side, and then over onto the other. Because of the step-by-step procedure, shaping is called the method of successive approximations.

Schedules of Reinforcements
The examples provided so far have all been cases of continuous reinforcement, because every response was reinforced. Alternatively, there are many ways to provide partial reinforcement, which involves less attention and expense because not every response is reinforced.

Reinforcement schedules may be timed according to either the ration or the interval of the responses. Ratio schedules involvce reinforcing every fixed number of response. Interval schedules involve reinforcing every specific time period, no matter how many responses have occurred.

In addition, both ratio and interval schedules can be either fixed or variable. A fixed schedule reinforces for the same ratio or interval everytime in the learning process. A variable schedule involves changing the ratio or interval between reinforcements from trial to trial.

According to research on schedules of partial reinforcement, the rates at which organisms learn and lose what they have learned depend both on the specific behaviour involved and the nature of the reinforcement schedule adhered to.
Extinction: Continuous Versus Partial Reinforcement
Extinction refers to the loss of an acquired response, or the failure to make a learned response. Extinction is brought about when, following a period of reinforcement for responding, reinforcement is no longer provided.
After continuous reinforcement, extinction is very fast. On the other hand, following partial reinforcement, extinction is typically very slow. This is called the partial-reinforcement extinction effect.
In human behaviour, there are similar effects. Parents who reinforce a child's crying on a partial schedule have a very difficult time extinguishing the crying behaviour.

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