What is forward chaining
SHAPING AND CHAINING
If a behavior never occurs, we say that it is not in the person’s repertoire. Shaping is a way of adding behaviors to a person’s repertoire. Shaping is used when the target behavior does not yet exist. In shaping, what is reinforced is some approximation of the target behavior.
Approximation means any behavior that resembles the desired behavior or takes the person closer to the desired behavior. Successive approximations are steps toward the target behavior, the behavior you want to shape.
In playing “Hot & Cold”, you reinforce any movement that takes the player closer to the prize. Each of those successive movements is a closer approximation of the desired behavior. If the prize is under the couch, and the player is moving toward the couch, every time the player takes a step toward the couch, you are yelling “hotter”, and you are reinforcing the behavior. If the player moves away from the couch, you would yell, “colder” (non-reinforcing).
The general rule is that you are reinforcing any behavior that is a closer approximation of the target behavior than the behavior you reinforced last. If a new approximation does not occur, you reinforce the last approximation again. If an approximation is repeated and reinforced three times, you can withhold reinforcement the next time that behavior appears.
If no new approximation appears, you have to drop back to a previously reinforced behavior. Sometimes you will get good progress for a while, only to have the child emit a behavior that was reinforced several steps before. You may then have to reinforce that old behavior and shape through the sequence again.
This procedure can be like helping someone up a staircase. Sometimes progress is effortless and goes quickly, other times it is slow and difficult. Sometimes the person may leap over the next step; then he may turn and go down the stairs a few steps and you have to help him up those same steps again. So, while the procedure is simple, it is not always easy to implement.
RULES FOR SHAPING:
- Define the target behavior: The behavior you want hasn’t occurred yet; it’s the goal at the end of the process, so you must decide what behavior is to be “shaped up”. To get to the target behavior, you must have a clear idea of what it is. Reinforce successive approximations of the target behavior: The target behavior is ‘shaped up’ by reinforcing the nearest approximations of that behavior. If the child gets stuck at a particular step, you can usually induce variability in behavior by withholding reinforcement. Some of the new behavior will be in the direction you want the behavior to go and can then be reinforced. Reinforce an approximation several times or until a closer approximation appears, whichever comes first. If no new approximation has appeared after several reinforcements, withhold reinforcement until a new approximation occurs. (Note: see handout “Prompting and Fading” to help encourage new approximations) In general, shaping progresses more rapidly when the increases in the requirements for reinforcement are small. When you hold out for something better, the something better should be only a very slight improvement. If an approximation appears that is a big advance, reinforce it’; but don’t hold out for big advances.
You will have to make judgments about when to raise the bar and by how much; sometimes, you will be wrong. If you err on the side of caution, reinforcing behavior at a given step more often than is necessary and making very small increases in the requirements for reinforcement, the worse that is likely to happen is that progress will be slow. If you make the mistake of moving too quickly, then progress will stop and you may see some strong emotional reactions. If progress breaks down, you can move back to a previous level.
- Monitor results: The only way you can gauge how successful you are being at shaping behavior is by noting what changes in behavior are occurring. Are you seeing progress toward the target behavior? Is the behavior that occurs now closer to the target behavior than the behavior you got earlier? Is it time to hold out for a closer approximation of the target behavior? Has the behavior begun to break down? Should you move back to a previous level? These are questions you must ask while shaping behavior and you can answer them only by paying close attention to changes in behavior. Taking data on each step, keeping track of approximations and levels of prompts help you determine answers. Graphing the data you’ve taken on a skill can help you determine the answers to many of these questions at a glance.
The new behavior you want to build may be a series or chain of behaviors. A behavior chain is a series of related behaviors, each of which provides the cue for the next and the last that produces a reinforcer.
Almost everything we do can be considered part of a behavior chain. For example, when you are reciting the alphabet, you start with “A”, then “B”, then “C” and so on until the task is completed at “Z”.
Each step serves as a cue for the next step; a chain is really a series of signals and behaviors. The completion of one behavior in a chain produces the signal for the next action. Saying “G” is the signal to say “H” next.
Practically any complex behavior we do in the way of operant behavior is part of a chain or a multitude of chains: eating, getting dressed, using the computer, counting, brushing your teeth, riding a bike, walking to school and so on. Behavior chains are very important to all of us; as is the procedure for building chains, which is called chaining.
Chaining is the reinforcement of successive elements of a behavior chain. If you are teaching your child the alphabet, you are attempting to build a chain,
if you are teaching the tying of shoelaces, you are also attempting to build a chain.
There are two chaining procedures, forward and backward chaining.
Forward chaining is a chaining procedure that begins with the first element in the chain and progresses to the last element (A to Z). In forward chaining, you start with the first task in the chain (A). Once the child can perform that element satisfactorily, you have him perform the first and second elements (A & B) and reinforce this effort. Do not teach “A”, then teach “B” separately; “A” and “B” are taught together. When these are mastered, you can move to “A”, “B” and “C”. Notice they are not taught in isolation; hence the term ‘chain’.
This is often a very effective way of developing complex sequences of behavior. In forward chaining, you are teaching A to Z; in backward teaching, you are teaching Z to A. Backward chaining is a chaining procedure that begins with the last element in the chain and proceeds to the first element.
To illustrate backward chaining, consider the following example: I want to teach my son complete a six-piece puzzle. The steps are:
- put in first piece put in second piece put in third piece put in fourth piece put in fifth piece put in sixth piece
To backward chain this task, I would follow steps one through 5 myself, presenting the task as completed except for the last piece. Then, I would (using whatever prompt level necessary) teach my son to put in the sixth piece (step 6). When he can successfully do this a number of times, I will teach step 5 & 6 (completing steps 1 through 4 myself beforehand).
Backward chaining this puzzle gave my son the idea of what he was doing ahead of time (there weren’t just a bunch of puzzle pieces laying there) and teaching in this way gives an even more clear clue of the next step. I would be reinforcing each step as I am teaching it, but once my son learns step 6, I will only reinforce steps 5 & 6 together (next link in the chain).
RULES FOR CHAINING:
- Define the target behavior: To teach someone to perform the links of a chain, you need to know exactly what those links are. Sometimes the links are very obvious as in the examples of teaching the alphabet, or the six-piece puzzle, other times links are not so obvious. It may be helpful to perform the target behavior yourself and take notice of all the steps involved, even have someone else watch you and compare notes. When teaching my son a bathroom routine, I was so proud of the links I thought up to produce the chain. I presented it to one of my workers who took one look at it and said “where does it say where he flushes the toilet?”.
Breaking the chain into small manageable steps is called performing a task analysis and a simple way of describing it is teaching A to Z and every single letter in between. Children with autism/pdd have shown that they can learn very effectively using this method.
- Reinforce successive elements of the chain. The elements in the chain must be reinforced in sequence. Reinforce them as they happen. Once your child has mastered step 6 and you begin to teach step 5, you will be reinforcing steps 5 and 6. You will either be reinforcing at the end of the chain or at the end of as much of the chain as the child has learned. What you learn in a chain is not just a number of tasks; you learn to perform those tasks in the right order. You can start at the beginning of the chain and work your way to the end or vice versa. Monitor Results. As with any intervention, you must keep track of the effects of your efforts. Has a particular element been mastered? Should it be taught and reinforced a few more times? Is it time to move on to the next element? These are judgments that must be made during the chaining process, and they can be made accurately only if you carefully monitor the results you are getting.
The similarity between shaping and chaining is that the goal in each case is to establish a target behavior that doesn’t yet occur. The difference is that shaping always moves forward. If progress breaks down, you may have to take a step back before moving forward again, but there is no such thing as backward shaping.
2: August 12, 2002
(c) BBB Autism – June 2002
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