QuasiExperimental and Single Subject small N Designs

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Quasi-Experimental and Single Subject (small N)
Designs

• Psychological Research Methods

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Quasi-Experimental Designs Examples (Adapted from
Salkind, 2000)

• Differences in the personalities of abused versus
  non-abused children
• Effect of malnutrition on infants
• Effects of maternal cocaine use during pregnancy
• Effects of pre-conception, paternal exposure to
  gametic mutagens
• Differences in intellectual capacity between old
  people placed in nursing homes and those living
  at home

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Quasi-Experimental Designs

• Non-equivalent Groups

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Quasi-Experimental Designs

• Proxy Pretest
• Recollection proxy-pretest
• Archived proxy-pretest
• Separate Pretest and Posttest Groups
• Switching Replications
• Test? Tx 1/2 ? Test ? Tx other 1/2 ? Test

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Differences between Experimental and
Quasi-Experimental Designs
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Differences between Experimental and
Quasi-Experimental Designs
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Differences between Experimental and
Quasi-Experimental Designs
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Differences between Experimental and
Quasi-Experimental Designs
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Differences between Experimental and
Quasi-Experimental Designs
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Single Subject (small N) Designs

• Nomothetic Research
• Idiographic Research

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Single Subject (small N) Designs

• Why use an N of 1?
• Clinical Interventions
• Rare Phenomena
• Challenge to status quo
• Pilot studies
• Interest in Individual Differences

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Single Subject (small N) Designs

• Procedures
• Baseline Measure
• Stability
• Treatment Measure
• Types
• AB
• ABA
• ABC
• Multiple Baselines across Behaviors
• Multiple Baselines across Subjects

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Single Subject (small N) DesignsTypes AB
A 6-month old girl who was born with a cleft
palate repeatedly engaged in forcing her tongue
to the back of her mouth which resulted in
vomiting. She did this behavior so frequently
that she was severely underweight, dehydrated,
and malnourished. Baseline observations indicated
that she was engaging in this behavior 50 of the
time while she was awake (Sajwaj et al., 1974).
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Single Subject (small N) DesignsTypes AB

• The Intervention
• Lemon juice
• The Result

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Single Subject (small N) DesignsTypes AB
At age 4, a young boy began engaging in extreme
hyperactivity, screaming, and self-injury. He
went through years of psychotherapy and drug
treatment, but nothing was successful. The self
injury included head banging, slapping, and
punching himself in the face. Baseline
measurements indicated that he was engaging in
approximately 400 self-injuries per hour. By the
age of 9 he was nearly blind and was frequently
tied to a bed to prevent further self-injury
(Tate Baroff, 1996).
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Single Subject (small N) DesignsTypes AB

• The Intervention
• Loss of human contact
• The Result

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Single Subject (small N) DesignsTypes AB
A 4-year-old boy was engaging in hyperactivity
and destructive behaviors. He would smash things,
knock over furniture, rip apart books, lick
things, spit, scream, and conspicuously wet his
pants. His behavior was destroying his family.
Baseline observations indicated that 60 of the
time he was engaging in these behaviors (Mace et
al., 1986).
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Single Subject (small N) DesignsTypes AB

• The Intervention
• Timeout
• The Result

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Single Subject (small N) DesignsTypes ABA
A 6-year-old autistic girl with an IQ of 20 was
engaging in self-stimulation and destructive
behaviors. The self-stimulation consisted of hand
flapping, arching her back, and flapping toys in
front of her eyes. She also threw toys and
scrapped the walls and furniture. Baseline
measurements indicated that she was doing this
over 80 of the time (Charlop et al., 1988).
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Single Subject (small N) DesignsTypes ABA

• The Intervention
• 5 second timeout
• The Result

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Single Subject (small N) DesignsTypes ABC
An 8-year-old boy with an IQ of 27 attended
special education classes. The boy would engage
in hyperactivity behavior which included running
around the class, yelling, throwing objects, and
grabbing people. He engaged in these behaviors
nearly 60 of the time (Foxx Shapiro, 1978).
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Single Subject (small N) DesignsTypes ABC

• The Intervention
• First rewarded good behaviors
• Then used modified timeout
• The Result

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Single Subject (small N) DesignsTypes ABCD
A mentally retarded man engaged in stereotypies
and self-stimulation such as head weaving,
repeated manipulation of objects, and rocking.
These behaviors prevented normal functioning
because they occurred almost 100 of the time
that he was awake (Jordan et al., 1989).
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Single Subject (small N) DesignsTypes ABCD

• The Intervention
• Reward for on-task behaviors
• Teaching phase
• Blocking vision for 5 second
• The Result

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Single Subject (small N) DesignsTypes Multiple
Baselines Across Behaviors
BASELINE BASELINE Tx
Tx
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Single Subject (small N) DesignsTypes Multiple
Baselines Across Subjects
Baseline Baseline Baseline
Tx Tx Tx
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Single Subject (small N) DesignsWhat would you
do?
A 10-year-old boy averaged 63 violent outbursts
per day in school. These outbursts included
chocking, hitting, pulling and pushing others, as
well as verbally abusing others. The outbursts
occurred with such frequency and violence that
the child had to be removed from the class for
developmentally disabled children (Luce et al.,
1980).
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Single Subject (small N) DesignsWhat would you
do?
A 10-year-old boy averaged 63 violent outbursts
per day in school. These outbursts included
chocking, hitting, pulling and pushing others, as
well as verbally abusing others. The outbursts
occurred with such frequency and violence that
the child had to be removed from the class for
developmentally disabled children (Luce et al.,
1980). Intervention Stand-sit
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Single Subject (small N) DesignsWhat would you
do?
A 32-year old Deaf woman who has been diagnosed
as profoundly retarded has been grinding her
teeth together for the past 14 years. As a
result, she has lost all but 5 of her upper
teeth, and her lower teeth are severely worn
away. Bruxism (teeth grinding) results in many
problems. It destroys the teeth. It results in
headaches, which make people irritable and
unresponsive. Others find the noise aversive
(Blount et al., 1982).
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Single Subject (small N) DesignsWhat would you
do?
A 32-year old Deaf woman who has been diagnosed
as profoundly retarded has been grinding her
teeth together for the past 14 years. As a
result, she has lost all but 5 of her upper
teeth, and her lower teeth are severely worn
away. Bruxism (teeth grinding) results in many
problems. It destroys the teeth. It results in
headaches, which make people irritable and
unresponsive. Others find the noise aversive
(Blount et al., 1982). Intervention Ice cubes
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Single Subject (small N) DesignsWhat would you
do?
A 63-year-old woman diagnosed with
undifferentiated schizophrenia was a 15 year
resident of a psychiatric hospital. She
repeatedly engaged in delusional verbal behavior.
The content of the delusions was often
graphically sexual (Ayllon Houghton, 1964).
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Single Subject (small N) DesignsWhat would you
do?
A 63-year-old woman diagnosed with
undifferentiated schizophrenia was a 15 year
resident of a psychiatric hospital. She
repeatedly engaged in delusional verbal behavior.
The content of the delusions was often
graphically sexual (Ayllon Houghton, 1964).
Intervention Ignore delusional verbal behavior/
Reward normal speech
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Single Subject (small N) DesignsWhat would you
do?
A 9-year-old girl who was diagnosed with mental
retardation, cerebral palsy, aphasia,
hyper-irritability, and brain damage would vomit
repeatedly in class, often targeting the teacher
and other students in the class. This was so
disruptive that she could no longer attend the
class. Repeated vomiting is harmful to the
esophagus, digestive tract, teeth and stomach
muscles. It also results in malnutrition (Wolf et
al., 1965).
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Single Subject (small N) DesignsWhat would you
do?
A 9-year-old girl who was diagnosed with mental
retardation, cerebral palsy, aphasia,
hyper-irritability, and brain damage would vomit
repeatedly in class, often targeting the teacher
and other students in the class. This was so
disruptive that she could no longer attend the
class. Repeated vomiting is harmful to the
esophagus, digestive tract, teeth and stomach
muscles. It also results in malnutrition (Wolf et
al., 1965). Intervention Extinction