Experimental Design:
Single-Participant
Designs/ The Operant
Approach
Single Subject Research

Single is a misnomer
– Multiple subject most often used
– Single relates to the unit of analysis

Involves
– Repeated observation of behavior
– Manipulation of one or more IVs on a WS
basis
– Demonstrations of stability within and across
levels of IV
 Trend and Bounce
Concepts in the experimental
analysis of behavior

Operant
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Length of phase

Phase

Changing phase

Baseline

Measuring the
response

Treatment
Phase

Phase
– The period of time during which the individual
is studied to see how his or her behavior
changes when different treatments are
introduced, withdrawn, or changed.
Baseline

Baseline phase
– The free level of the operant or response is
measured.
– Need to know how strong the target behavior
is before we can assess any changes that
might occur in its strength when we introduce
a treatment.
– Baseline measurements need to be taken for
long enough so that we have a good idea of
what the operant level is prior to treatment.
Treatment

The IV is introduced and the behavior is
carefully measured and recorded.

Treatment usually involves some kind of
reinforcement of punishment procedure.

Reinforcement procedure – where the
operant response is followed by a stimulus (the
reinforcer) intended to increase its strength.

Punishment procedure – where the behavior
is followed by a stimulus (the punisher) intended
to reduce its strength.
Length of phase

Length of phase
– Depends on the stability of the behavior being
observed.
– Each phase generally continues until the
target behavior is stable or consistent over
time.
Changing phase
Once we see a consistent level of responding we
can introduce, withdraw, or change a treatment.
 Goal  to show that our treatment causes a
change in the operant level.
 Interpretation of the results is more subjective
than in multiparticipant research where the
statistical analysis provides more objective
answers.
 Results should be replicable.

Measuring the response

Various measures of response strength:
– Rate or frequency of responding in a specific
period of time.
 Cumulative record – total frequency of the operant
behavior and the time when the response
occurred.
 Data often displayed in a cumulative response
graph.
 Use graphic analysis to determine whether or not
the IV had an effect .
ABA and ABAB withdrawal
designs






A – Baseline phase
B – Treatment phase
Second A – Withdrawal of treatment
ABA design – gather baseline data (A), then
introduce a treatment (B), and then withdraw
the treatment and measure responding again
(A).
Withdrawal of treatment acts as a control and
allows us to establish a causal relationship.
ABAB design – includes a second treatment
phase (e.g. used in behavior modification).
Graphical Presentation
Graphical Presentation
Multiple baseline design

Multiple baseline designs
– Allow us to assess our treatment by comparing
its effect on different behaviors, settings, or
people rather than by withdrawing treatment.

Advantage of multiple baseline design over
withdrawal designs: baseline conditions are not
reintroduced after treatment has begun.

Therefore, they are useful for studying treatments
that we expect to be permanent or long-lasting.
Multiple baseline design

Multiple baseline across participants design
 Introduce treatment in two or more
individuals.

Multiple baseline across behaviors design
 Introduce treatment for more than one
behavior.

Multiple baseline across settings design
– Measure our targeted behavior in different
settings and apply treatment in one setting at
a time.
Alternating treatment design

Useful for evaluating the effect of more than one
treatment on the behavior of an individual within
an experiment.

After the baseline phase, different treatments
are alternated several times. The order of the
treatments is randomly determined or
counterbalanced to control carryover effects.

Each treatment effect is replicated each time it is
introduced. A treatment may be applied a few
times or many times.
Changing criterion design

Use when a goal behavior can be
quantified into different target levels or
steps.

When the behavior reaches the targeted
level, the criterion is changed, and the
behavior must meet the new criterion.

The final goal behavior is reached in a
step-wise fashion.
Component-analysis design
This design consists of a series of phases in
which each phase adds or subtracts one
component of a complex treatment to determine
how each component contributes to the overall
treatment effectiveness
 Example – Studying reward and punishment for
biting behavior in an autistic boy BC-B-BC-C-BC
BC – combination of the reward and punishment
B – reward only
C – punishment only

Advantages and disadvantages
of single participant designs
Single participant designs are particularly well
suited in clinical settings as causal links can be
established. This can also be a disadvantage as
a treatment that works for one individual may
not work for others, in which case the study
lacks external validity.
 Conditions can be tailored to the individual being
studied rather than standardized for a group.
The researcher can easily modify the design
even after the study has begun without
jeopardizing its integrity.

Advantages and disadvantages
of single participant designs
Using response rate as the primary DV can
be a disadvantage because other
measures of behavior (e.g.. number
correct, reaction time, rating, etc.) are
excluded.
 Single participant designs use a seemingly
more subjective approach that relies on
the experience and integrity of the
researcher. This can be seen as both a
strength and a weakness.

Advantages and disadvantages
of single participant designs

The single participant approach can be
viewed as offering the best of both worlds
to clinicians  treatment can be provided
at the same time that cause and effect is
demonstrated. This meshing of
experimental research and clinical practice
is perhaps the biggest strength of single
participant designs.