Small N research

1. Small N research

2. 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

3. 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

5. 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

6. 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

7. 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

8. Case Studies • intensive description of individuals • source of hypotheses and ideas • clinical • child development • animal behaviorists • anthropology • criminology • neurology • sociology • bogus science (anecdote)

9. 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

10. 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)

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13. ABAC, ABACAB…. • Increase complexity designs • Baseline Treatment Baseline Control • Eg placebo • Or • Baseline Treatment1 Baseline Treatment2

14. 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

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17. Changing criterion • Gradual approximation to ideal behavior • Shaping – must be individual • Eg Desensitization - reduce fear of snakes • Or exercise and obesity