Outline 1.Definition a.Case Studies b.N=1 Studies 2.Advantages of Case Study approach 3.Disadvantages of Case Study approach 4.Examples of Case Study approach Case

Definition Single-subject studies are those in which the focus is on the performance of individual subjects rather than groups of subjects. Even when more than one subject is studied in a single-subject design, data are analyzed one subject at a time (hence the name). Case

Two kinds of single-subject studies Case studies intensive description and analysis of the performance of one subject. N=1 studies independent variable is manipulated within an individual. (This is an experiment.) Case

Case Studies - advantages Focusing on big effects in group studies with very large n, even trivial effects may be statistically significant. Case

Case Studies - advantages Focusing on big effects Focusing on individual performance sometimes, averages distort – that is, no individual’s performance may be qualitatively like the average. Case

Case Studies - advantages Focusing on big effects Focusing on individual performance Reducing ethical problems if a treatment has bad side- effects, harm is minimized. Case

Case Studies - advantages Focusing on big effects Focusing on individual performance Reducing ethical problems Breeding hypotheses Case studies are a breeding ground for hypotheses in research areas about which little is known Case

Case Studies - advantages Opportunity for clinical innovation tailor treatment to a particular patient’s circumstances and symptoms Case

Case Studies - advantages Opportunity for clinical innovation Study rare phenomena E.g., “wild boy of Aveyron,” (R. Shattuck, 1994) – How are we different from animals? How do we learn language? What is “natural?” Case

Case Studies - advantages Opportunity for clinical innovation Study rare phenomena Challenge theoretical assumptions providing a “counter- instance” – a single case that violates a universally- accepted idea. E.g., Genie data tested critical period hypothesis. Case

Case Studies - advantages Opportunity for clinical innovation Study rare phenomena Challenge theoretical assumptions Tentative support for a theory E.g., patient HM – taken as supporting Atkinson & Shiffrin’s (1968) model of memory Case

Case Studies - advantages Opportunity for clinical innovation Study rare phenomena Challenge theoretical assumptions Tentative support for a theory Complements nomothetic study of behavior Allport: clinician wants to know what a given person may do, not what people do “on average” idiographic approach (study of an individual) yields details that may lead to new ideas about behavior. Case

Case Studies - disadvantages Difficulty of drawing cause- effect conclusions case studies usually do not control extraneous variables. e.g., if a patient improves, was remission spontaneous? Was it the treatment, or the attention? Case

Case Studies - disadvantages Difficulty of drawing cause- effect conclusions Possible bias in data collection does patient give self- reports? Are they true? are data based on memory? Case

Case Studies - disadvantages Difficulty of drawing cause- effect conclusions Possible bias in data collection Possible bias in interpreting data if researcher is both therapist & observer. is ‘effect’ of treatment a matter of therapist’s impressions? does researcher have a lot invested professionally or emotionally in the success of the approach being studied? Case

Case Studies - disadvantages Difficulty of drawing cause- effect conclusions Possible bias in data collection Possible bias in interpreting data if researcher is both therapist & observer. Problem of generalizing from one individual depends upon variability in population e.g., for vision research – little problem for personality research – potentially a big problem Note: even data that cannot be generalized widely may have a role in theory testing (see Stanovich). Case

Case Studies – some examples Sigmund Freud argued that in order to have enough information about patient to do any good, you have to do case studies you have to work for years to know patient at all because the mind is so complex Case

Case Studies –some examples Memory patient HM bilateral removal of medial temporal lobe, to relieve severe epilepsy. profoundly amnesic as a result – capable of little new (declarative) learning cannot extend his digit span in the normal way Case

Case Studies –some examples Memory patient HM this case very important for theory of separate Short- term and Long-term Memory systems. HM thought to have intact STM, damaged LTM – cannot get new information into LTM. Case

Case Studies –some examples Stevens et al. (Vision Research, 1976) – Corollary discharge theory Command sent to move eyes; copy of the command sent to visual processing centers. Researchers injected themselves with curare, to paralyze eye muscles, then tried to move eyes. Saw world move in opposite direction… Case