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Small N research
Many early psychology studies of small n
• Fechner - visual psychophysics• James - introspection • Piaget - child development (his 3 children)• Freud - case studies• Skinner - conditioning “Instead of studying a thousand rats for one hour each, or a hundred
rats for ten hours each the investigator is likely to study one rat for a thousand hours”
• Inductive -specific to general principles• Very little statistical analysis
Why small N
Averaging can be misleading - the data looks like nobody (subject validity failed)
May be better to look at each individually
Group data can smear or disguise differences
Could support or refute theory erroneously
• Participants are rare
• Memory research eg H.M.• Clinical impact eg Phineas Gage
• Study of expertise – eg chess masters• Rare disease/ disorder eg Capgras
syndrome
Even a single case study can challenge a theory or act as a source of new hypotheses about normal and abnormal behavior.
• Ramachandran’s pig
Problems
• No valid causal inference if extraneous variables uncontrolled (particularly n=1)
• Often naturalistic and treatments uncontrolled• Interactions hard to observe
• Observer bias (esp clinical therapist)• Generalizability depends on population variability
eg visual system vs personality
Case Studies
• intensive description of individuals• source of hypotheses and ideas
• clinical• child development• animal behaviorists• anthropology• criminology• neurology• sociology• bogus science (anecdote)
Designs
• Single case study
• Naturalistic observation, interviews, tests- usually detailed information about many aspects of one person often not easy to compare with another person
• Often good for generating ideas or customizing treatment
Baseline, AB, ABA, ABAB
• Baseline shows underlying variability gives basis for comparison
• Establish target behavior
• Researcher manipulates variable
• If can withdraw treatment then ABAB best
(finish on treatment – ethical)
Text eg
ABAC, ABACAB….
• Increase complexity designs
• Baseline Treatment Baseline Control
• Eg placebo
• Or
• Baseline Treatment1 Baseline Treatment2
Multiple baselines
• Time differences in baseline and treatment
• Same type of behavior in 2 or more people
• Two or more behaviors in same person - hair pulling and head banging
• Same behavior different settings - social responding at breakfast and lunch
text
Changing criterion
• Gradual approximation to ideal behavior
• Shaping – must be individual
• Eg Desensitization - reduce fear of snakes
• Or exercise and obesity
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