Chapter 9
Overview of Alternating Treatments Designs
Background/Overview
• Alternating Treatments Designs (ATD)
requires the “rapid alternation of two or
more distinct treatments while their effects
on a single target behavior are noted.”
• ATD does not require the collection of
baseline data. However, when possible it
should be collected.
Background/Overview
• Two important points
– The presentation of the treatments should be
counterbalanced (presented the same
number of times).
– The subjects should be able to discriminate
between or among the treatment conditions.
Three types of ATD
• Alternating treatments without baseline
• Baseline followed by alternating
treatments
• Baseline followed by alternating
treatments with a final treatment phase.
Alternating Treatments w/o
Baseline
• This treatment can be implemented
immediately.
• This design should actually include a type
of baseline data by having a no-treatment
phase as one of the alternating treatments
(Alternating treatments with a control
condition design).
Baseline Followed by ATD
• Two situations when gathering a baseline
should not continue.
– When the nature of the target behavior is
severely ethical (Self-abusive behaviors).
– When the data trend is moving in a
countertherapeutic direction.
Baseline Followed by ATD
• Four steps to follow:
– Carefully define the independent and dependent
variables.
– Determine a schedule for counterbalancing the
presentation of the treatments.
– Collect baseline data for the dependent variable
for a number of sessions (baseline phase does
not have to be stable before introducing the
treatment).
– Introduce treatments in their predetermined order.
Baseline Followed by ATD and a
Final Treatment Phase
• It is important to continue the most
effective treatment.
• Therefore, one would collect baseline,
introduce alternating treatments, then
continue the study using the most effective
treatment.
Prediction, Verification, and
Replication
• There are some concerns:
• The determination of a functional relationship
b/w the DV and the IV is weak compared to
reversal and multiple baseline designs.
• The possibility of multiple treatment
interference might produce carryover effects
that obscure the relationship of the DV to IV.
• External Validity must be addressed by
replicating with different subjects and/or
conditions.
Prediction, Verification, and
Replication
• Cooper et al. argued that ATD addresses
each of the preceding issues:
• Prediction: each data point serves as a
predictor of future behavior under the same
treatment.
• Verification: Each successive data point
serves to verify previous predictions of
performance under the same treatment.
• Replication: Successive data points
replicates the differential effects produced by
the other treatments.
Prediction, Verification, and
Replication
• Neuman (1995) points out thatATD may have
good internal validity for two reasons.
• The patterns of response vary with the
alternating treatment conditions, so there is
minimal overlap among data in the
conditions.
• If one treatment is consistently associated
with an improved level of responding, then
the design demonstrates good experimental
control.
Important
• The choice to use ATD, or any other
design, should be based on a careful
match of the dependent and the
independent variables.
Advantages of ATD
• When you want to determine the relative
effectiveness of more than one treatment on a
given behavior.
• When baseline data are either unavailable or
unstable.
• When the treatments are sufficiently different from
each other.
• When the subjects can discriminate the treatment
conditions.
• When the effects of sequencing the interventions
might obscure the results.
Disadvantages of ATD
• When the treatments might interact and obscure
results.
• When the subjects cannot discriminate the
treatment conditions.
• When the treatments typically produce slow
behavior changes.
• When the treatments need to be administered
over a continuous period of time to be effective.
• When it becomes difficult to counterbalance the
various aspects of the study.
Adaptations of ATD
• Simultaneous Treatment Design
• This is rare in professional literature
• Treatment conditions are presented at the
same time.
• Requires more skill, planning, and
organization that the use of other designs.
• It is difficult to systematically analyze the
effects of several interventions presented
at the same time.
Adaptations of ATD
• Adapted Alternating Treatments Design
• Each intervention is applied to different
behaviors that are considered to be of
equal response difficulty but functionally
independent.
• The process of equating behaviors can be
time consuming and problematic.