Overview of Withdrawal
Designs
Chapter 5
Withdrawal Designs
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Withdrawal- refers to the withdrawal of
treatment during one or more phases of a
study to demonstrate the effects that it has on
the target behavior
Typically represented by the letters A-B-A-B
(A represents baseline, B represents
intervention).
Its more common name is reversal design.
A-B Design
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Most basic of all single subject designs
In this design the researcher collects
baseline data (A) and then implements
a treatment (B).
This is done to determine its effect on
target behavior.
Weakness of A-B Design
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Most weakest of all single subject
designs since the functional relationship
between the dependent and
independent variables are not firmly
established.
There are several factors that can play
a role on the dependent variable (e.g.
maturation, practice effects).
Mechanics of Withdrawal
Designs
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The goal of withdrawal designs is to
show a functional relationship between
the target behavior and the intervention.
This occurs when the experimental
control is increased when the
intervention is subsequently withdrawn
so that baseline conditions are again in
effect resulting in A-B-A design.
A-B-A Design
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First step
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Second step
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Define both the target behavior to be altered and the
treatment to be implemented.
Collect baseline data (A) for at least 5 consecutive
days or until baseline trend is established.
Third step
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Introduce treatment (B) or intervention and collect
continuous data either until a specific criterion has
been met or until a stable mode of responding in the
desired direction is recorded.
A-B-A Design cont.
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Fourth step
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Withdraw treatment or return to baseline phase
(A).
If the target behavior improves in the desired
direction during the intervention phase and
changes toward baseline levels once the
treatment is withdrawn, the experimenter can
conclude that treatment was responsible for
the improvement of target behavior.
A-B-A-B Design
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In this design experimenter must define the
target behavior and the intervention to be
used before collecting data.
Involves a no-intervention baseline(A1) and
an intervention phase (B1), with each phase
being repeated (A2 & B2).
The logic is to strengthen or validate the
functional relationship between target
behavior and treatment
Prediction, Verification, &
Replication
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Describes A-B-A-B design
Predict- after stable baseline (A1) data
are collected, one would predict that the
same pattern would remain under the
same conditions.
However, if the treatment (B1)has an
effect, one would predict that a different
pattern would emerge.
Prediction, Verification, &
Replication cont.
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Verification- occurs when the change
from baseline to intervention phase
results in a change in responding.
In other words it occurs when return to
the baseline condition (A2) results in a
pattern similar to the original baseline
condition (A1).
Prediction, Verification, &
Replication cont.
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Replication- occurs when second
treatment phase (B2) results in a similar
response pattern as the previous
treatment phase (B1).
The reintroduction and withdrawal of
the introduction more than once
strengthens the evidence of prediction,
verification, and replication.
Advantages of the
Withdrawal Design
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Is one of the easiest single subject
designs to implement.
Possess great flexibility
Can be used when the withdrawal of a
particular treatment will reverse the
target behavior to baseline, or preintervention levels.
When to use the withdrawal
design:
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When a clear functional relationship between the
independent and dependent variables needs to be
demonstrated
When the nature of the target behavior is such that
it can be reversed when the treatment is
withdrawn
When the nature of the treatment is such that its
effects are not present on the target behavior after
it’s withdrawn
When withdrawal of treatment does not
compromise ethics
Disadvantages of the
Withdrawal Design
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The goal of the withdrawal design is
antithetical to educational or clinical goals.
Resentful Demoralization may occur,which
means that individuals’ behaviors during
subsequent baseline conditions might be
negatively affected by resentment over
having the treatment withdrawn.
A great concern is using the withdrawal
design with dangerous behaviors.
When not to use the
Withdrawal Design
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When the target behavior is not reversible.
When the treatment effects will continue after
the treatment is withdrawn
When it is not educationally or clinically
desirable for the behavior to return to baseline
levels
When the target behavior is such that
withdrawal of effective treatment would be
unethical (e.g. dangerous behavior).
Adaptations of the Typical
Withdrawal Design
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B-A-B Design:
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When the use of A-B-A or A-B-A-B design are not
appropriate, the B-A-B design can be used.
In this design the experimenter begins with the
application of the independent variable (B
phase).
Once intervention phase produces stable
responding at an acceptable level, the treatment
is withdrawn.
The A-B-A-B-A-B
(Repeated Withdrawals)
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In this design the treatment variable is
introduced and withdrawn repeatedly.
Repeated withdrawals increase
confidence in the functional relationship
between the treatment and the target
behavior.
The A-B-C
(Changing Conditions)
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In this design (A) represents baseline, B
would indicate treatment 1, and C would
indicate treatment 2.
Any number of treatment conditions
could be introduced (A-B-C-D or A-B-CD-E) with the goal to end the design in
an effective treatment condition.
The A-B-A-C Design
(Multiple Treatments)
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In this design, the C phase may be an
alteration to the original treatment introduced
in the B phase or it may represent a new
treatment altogether.
Investigator collects baseline data (A),
introduces the intervention variable (B), and
then withdraws it as in an A-B-A design.
Then the investigator introduces a second
intervention.
Multiple Treatment Design
Considerations
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Make sure that only one variable at a time is
changed from one phase to the next.
Understand limitations of the functional
relationships established
The time necessary to complete many
experiments using this design with many phases
can result in threats to internal validity.
Note that a treatment that is offered only in
combination with another cannot be adequately
evaluated for its effectiveness alone.