1 Single-Case Research Designs PS1006 Lecture 6 Sam Cromie

2 Group Vs Single Case Designs Group designs: Average performance of a group Comparing average performance between groups Group variability Statistical significance Single case designs: Actual performance of an individual Comparing individual performance in different conditions Individual variability Clinical significance

3 Examples of SC Resesarch Ebbinghaus (1885) - participant and experimenter - first systematic evidence of forgetting over time Freud’s psychoanalytical case studies Behaviour Analysis – SC experiments with pigeons, monkeys, humans Psychophysics, study of expert performance e.g., chess players & musicians, Oliver Sacks - ‘The Man Who mistook His Wife for a Hat’

4 Single case studies - characteristics Intensive description and analysis of single individual. Data obtained through: naturalistic observation, interviews, psychological tests, experimental measurement May describe the application and results of a particular treatment.

5 Case Studies (CS) vs Single Case Experiments (SCE) Exploratory Qualitative May generate hypotheses for experimental research Experimental manipulation IVs and DVs Operational definition Measurement Hypotheses 6+ participants

6 Advantages of Case studies Provide new ideas and hypotheses –Open the way for discoveries based on other methodologies –Provides opportunity to develop new clinical techniques Try out new clinical techniques the utility of which may only become apparent in specific cases

7 Provides chance to study rare phenomena –Infrequent occurrences can only be examined through intensive study e.g., Feral children - ‘The wild boy of Aveyron’ - Victor - Lived alone in woods from ages of 5- 11/12 ‘The forbidden experiment’ - Genie –Such cases do not offer definitive answers rather ‘obliges us to reflect on how to live with these unsolved questions’ - (Shattuck, 1994, p182) Advantages

8 Can support or challenge scientific theories –Falsificationism Genie was found at 13 never having learned to communicate due to lack of human interaction. Lenneberg proposed critical period of language development = 2-puberty Lenneberg theory could be tested by determining whether Genie could now acquire language. Genie showed some language development but was never completely normal Lenneberg’s theory at the very least should be modified after the evidence ‘provided’ by Genie Advantages

9 Can support or challenge scientific theories –Atkinson and Shiffrin’s multi-storey theory of memory gets considerable support from patients who show specific breakdowns in one part of the memory system. –H.M. could have conversation and remember events for short periods of time but could not form new memories. Advantages

10 –Individual is more than can be represented by the collection of average values on various dimensions. –Has the ability to reveal various nuances and subtleties of behaviour that a group approach may miss. Advantages

11 Difficulties of Case studies Difficulty of drawing cause-effect conclusions –Illnesses can subside spontaneously –Other aspects of the patient-therapist relationship may have an impact –Genie - a Doctor’s examination at 14mnths lead to the comment that she was possibly retarded - there is no way of concluding that Genie’s disposition was a product of the poor environment which she inhabited.

12 Biases –In interpretation –Data collection. Archival records or information based on self-reports are particularly vulnerable. Lack of generalisation –Difficult to generalise from case to case. –Except where it is assumed that the underlying physiological/behavioural systems are shared e.g. psychophysics assumes that for example visual systems are based on a shared physiological makeup Difficulties of Case studies

13 Public often considers personal testimony as measure of efficacy –In 1980’s Laetrile, made from apricot pits, supposed to be beneficial to the treatment of cancer. By using Laetrile instead of traditional therapies, many patients may have postponed valid courses of treatment and thus contributed to the spread of their cancer. Difficulties of Case studies

14 Single-Case Experimental Designs Core tool of Behaviour Analysis (Skinner) Manipulating single IVs and measuring behavioural change in one individual Baseline compared with intervention phases Assumes the behavioural principles are universal, across individuals and organisms Graphical depiction of results Impact of results visually rather then statistically determined – “if the difference is not obvious it is not significant”

15 Basic SC experimental designs A= Baseline; B= Intervention 1; C= Intervention 2 AB – weak design ABA – reversal procedures adds to predictive power, but ends up with baseline ABAB – even more predictive power and ends up with intervention ABC, ABAC, ABCD, etc. Problems: –ethics of withdrawal, –intervention may have non-reversible effects – collateral reinforcement, verbal behaviour

16 AB design A B

17 ABAB Design Experiment

18 An ABC design experiment

19 Multiple baseline designs An independent variable is sequentially applied to at least two dependent variables Multiple baseline –Across behaviours –Across settings –Across participants Avoid problems of reversals while still demonstrating the impact of the independent variable

20 Multiple baseline design

21 Changing criterion designs Progressively change the level of the target behaviour required for reinforcement Track changes relative to the criterion

22 Changing Criterion Design

23 Readings Concise Overview: Leslie & O’Reilly Behaviour Analysis: foundations and applications to psychology Chapter 8 More detail: Cooper,J; Heron,T; Heward,B; Applied Behaviour Analysis nd Edition