Single-Case Research Designs

PS1006 Lecture 6 Sam Cromie 1

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 2

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’ 3

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. 4

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 5

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 6

Advantages

• 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 the se unsolved questions’ - (Shattuck, 1994, p182) 7

Advantages

• 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 8

Advantages

• 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.

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Advantages

– 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.

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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. 11

Difficulties of Case studies

• 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 12

Difficulties of Case studies

• 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.

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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” 14

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 15

15 20 25

A

Baseline

AB design

Jack

Token Economy/ DRO.

B

10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 13

No. of Days

14 15 16 17 18 19 20 21 22 23 24 25 Series1 16

ABAB Design Experiment

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An ABC design experiment

Junior Infants

120 100 80 Baseline Training Token Economy 60 40 20 0 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58

No of Sessions

Series1 18

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 19

Multiple baseline design

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Changing criterion designs

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

Changing Criterion Design

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Readings

Concise Overview: • Leslie & O’Reilly

Behaviour Analysis: foundations and applications to psychology

1999. Chapter 8 More detail: • Cooper,J; Heron,T; Heward,B;

Applied Behaviour Analysis

2007 2 nd Edition 23