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
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”
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
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:
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.
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
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
To illustrate backward chaining, consider the following
example: I want to teach my son
complete a six-piece puzzle. The steps are:
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
RULES FOR CHAINING:
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.
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.
CHAINING DATA SHEET
2: August 12, 2002
BBB Autism – June 2002
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