Earlier in this course, you learned that behaviour is everything a person does ? that involves the movement of the organism (or a part of the organism) through space and time.
In subsequent lessons, we?ve mentioned dozens of behaviors. However, you may have noticed that some of these behaviours could be broken down into lots of other behaviours. Many behaviours that we carry out every day (e.g. tying shoes, driving a car, making a meal etc.) can be broken down into steps that need to be performed in a particular sequence in order to produce a reinforcer. This sequence of behaviours is known as a Behaviour Chain.
In a Behaviour Chain, each response provides a cue to engage in the next response except for the final behaviour in the chain which produces a reinforcer.
That is, after the presentation of the natural SD, the first behaviour in the chain occurs. Its consequence affects the environment. This change acts both as a conditioned reinforcer for the previous behaviour and an SD for the next behaviour. The final step in the chain produces the terminal reinforcer.
For example, if a worker in a sandwich shop is asked to make a cheese sandwich, the customer?s request is the initial SD. This leads to the first behaviour ? getting slices of bread and putting them on a sandwich board. The bread on the sandwich board serves as the SD for the second behaviour of buttering the bread. The buttered bread serves as the SD for placing cheese on one slice of bread. This then serves as the SD for putting the other slice on top of the bread. The uncut sandwich serves as the SD for cutting the sandwich with the cut sandwich serving as an SD for packaging it. The packaged sandwich serves as the SD for handing the package to the customer which produces reinforcement in the form of social reinforcement from the customer and from colleagues.
Another example, would be putting together flatpack furniture. The completion of each step functions as the SD for the next step. And task progression usually functions as reinforcement. The terminal reinforcer is seeing and using the completed furniture.
When teaching behaviour chains, we usually use something known as a TASK ANALYSIS. This involves breaking a complex behaviour into small, teachable steps. Prompting and Reinforcing each step within a TASK ANALYSIS is an instructional procedure known as chaining.
There are three types of chaining procedures used in ABA. These are:
Backward Chaining – All of the behaviours identified in the task analysis are initially completed by the trainer, except for the final behaviour in the chain. Reinforcement is first contingent on completion of that final step only at the target prompt level. When the final step is consistently being performed independently, you target the 2nd last behaviour in the chain ? moving backwards until all steps in the chain are mastered. It is often used if the reinforcer at the end of a chain is quite strong for a learner and if the target skills is quite difficult for an individual learner.
Forward Chaining ? in which the sequence of behaviour in the task analysis is taught in their naturally occurring order. You begin by starting with the learner performing any learned steps in their order up to the first unmastered step, at which point instruction begins. If necessary, the unmastered step is prompted and reinforcement is given immediately after the training step. The remainder of the chain can be completed by the trainer or the learner but the routine should be finished before another training opportunity is provided. It is often used if the reinforcer at the end of a chain is not strong for a learner and if the target skills is quite difficult for an individual learner.
Total Task – The learner receives training on each step in the task analysis during every session. Each step has its own target prompt level. The chain is trained until the learner is able to perform all of the behaviours in the sequence to the predetermined criterion. It is usually used if a learner can already carry out some steps in a chain independently