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Molding or method of successive approximations: uses and characteristics

Molding or method of successive approximations: uses and characteristics

September 27, 2022

Molding is a technique that is used to promote learning, especially in children with special needs. It was first described by the psychologist B. F. Skinner, father of operant conditioning, and was a fundamental milestone in the development of this behavioral paradigm.

In this article we will explain what is the molding, also called "method of successive approximations" because it basically consists in reinforcing a behavior selectively so that it ends up adopting a certain topography and function. We will also talk about some of the operant techniques that are usually used together with the molding.

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What is the molding?

Molding is a learning paradigm that is part of operant conditioning . In the context of the analysis of applied behavior, which was developed by Burrhus Frederick Skinner, behavior modeling is usually carried out through the method of differential reinforcement by successive approximations.


These procedures are based on the progressive modification of an existing response in the behavioral repertoire of the subject who learns. By selectively reinforcing behaviors that are more and more similar to those to be established, these are strengthened while those that are less precise tend to be extinguished due to the lack of contingency with reinforcements.

A) Yes, the fundamental mechanism of these behavioral techniques is the reinforcement , particularly the differential type. Since the mid-twentieth century we know that it is more efficient to focus the processes of instruction in the reinforcement of desirable behaviors than in the punishment of other incorrect ones, both for ethical and for other purely practical reasons.


Molding is one of the operant techniques that serve to develop behaviors. In this sense, it is similar to chaining, in which learning consists of combining simple behaviors present in the subject's repertoire with the aim of forming complex behavioral chains, such as starting a vehicle or playing a musical instrument.

A special variant of this working paradigm is self-molding, in which a conditioned stimulus is matched as another unconditioned without the behavior of the learning subject influencing the process. So, Self-molding is not included within operant or skinnerian conditioning but the classic or Pavlovian.

The method of successive approximations

To apply the shaping and the method of successive approximations it is necessary first of all to determine what is the final behavior that the subject must learn to execute. Next, their repertoire of answers is evaluated, usually through behavioral tests, to identify one that could be a good starting point for learning.


In particular, the objective is select a behavior that the subject can carry out without problem and that it resembles as much as possible the objective response, both in its topographical aspect (eg, the type of muscular movements involved) and in the functional one; This term refers to the goal or function that meets a certain behavior.

The next step is to determine the steps that will lead from the initial behavior to the final one, that is, the successive approximations to the objective behavior . It is advisable to test the sequence before applying it and, if necessary, it is also convenient to review it during the molding process in order to enhance its effectiveness.

Molding has been used successfully in a large number of different applications. Among the most relevant are special education (such as cases of autism and functional diversity in general), motor rehabilitation after injuries and sexual dysfunctions; The Masters and Johnson method to treat erectile dysfunction is a good example.

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Operant techniques associated

In general, the modeling is not applied in isolation, but in a context of broader intervention: the paradigm of operant conditioning, and in particular in the analysis of applied behavior, which was developed by Skinner and in which originally many of the operating techniques that we know today. This was based on associating certain actions with the stimuli produced by the effects that this behavior has when applied to the environment.

To enhance the effectiveness of the successive approximation method, usually combined with other operating procedures . In this sense, it is worth mentioning the application of discriminative stimuli that inform the subject that if he emits the correct behavior, he will obtain reinforcement and the progressive fading of these.

The final goal is that the target behavior be controlled by natural reinforcements, such as social ones (such as smiles and even attentive looks), and not by discriminative stimuli, which are a good way to develop behaviors but not keep them. This process can be called "transfer of stimulating control".

Other operating techniques that are often associated with molding are modeling , which consists of learning through the observation of the behavior of others, verbal instructions and physical guidance, which would occur when a psychologist moves the hands of the child who is helping to educate to indicate how to use a zipper.


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