Single Case Research Designs

Outline of Today’s Discussion The Case Study Method Single Case Experimental Designs

Part 1 The Case Study Method

The Case Study Method Throughout the semester we have focused on group methodology. Single-case research is an alternate type of design, in which N = 1. This research is sometimes referred to as small N research…as there are studies that focus on, say, 2 or 3 participants.

The Case Study Method Some of the earliest, and most enduring findings in psychology were discovered by single case research. Example 1: Gustov Fechner’s psychophysics. What is psychophysics? Example 2: Hermann Ebbinghauss’ memory work. What was Ebbinghauss’ contribution?

The Case Study Method Two broad categories of single-case research are the case study, and single-case experimental designs. We’ll discuss each in turn… Case Study - an intensive description and analysis of a single individual. Examples: Oliver Sacks’ neurological patients: “The man who mistook his wife for a hat”; “At First Sight”. http://en.wikipedia.org/wiki/At_First_Sight

The Case Study Method Case studies offer several advantages… Sources of ideas about behavior: We can learn about a system (e.g., the central nervous system) when it breaks. Opportunity for clinical innovation: Example: A study might show success with a day-long session on combat guilt. Follow-up studies could show replicability.

The Case Study Method Method to study rare phenomena: Some studies would be unethical to conduct by deliberate manipulation, but are ethically feasible if the same manipulation occurred “naturally”. Perceptual psychologists would love to know how motion perception is affected when brain area “MT” is surgically removed…. We have to wait for a case study, involving brain damage by stroke or accident. PubMed Abstract on “motion-blind” patient http://www.ncbi.nlm.nih.gov/pubmed/2723744

The Case Study Method Challenge to theoretical assumptions: A single example can falsify an absolute statement. Tentative support for a Psychological Theory. Could someone describe the case study on HM, and why it was important for a theory positing separate neural mechanisms for short term and long term memory? http://en.wikipedia.org/wiki/Henry_Molaison

The Case Study Method There are also disadvantages associated with the case study method.. Observer bias! Generalizability! Difficulty in drawing cause-effect conclusions: This arises primarily from a lack of experimental control…

The Case Study Method Research Methods Differ in Control

Single-Case Experimental Designs Part 2 Single-Case Experimental Designs

Single-Case Experimental Designs Single-Case experimental designs - a paradigm in which N=1, and there is tight control over independent variables. “Rather than studying 1,000 rats for one hour each, one rat is studied for 1,000 hours” (Skinner). Inferential stats are rarely used in this paradigm. Conclusions are drawn by visually inspecting the behavioral record showing systematic changes with the introduction and withdrawal of the I.V.

Single-Case Experimental Designs From Skinner, (1956). American Psychologist, 11:221.. Single-Case Experimental Designs I don’t want to know how to change behavior on average, I want to know how to change behavior…period!

Single-Case Experimental Designs Applied Behavior Analysis (ABA) - The application of techniques from single case experiments to socially relevant problems. ABA has been successful in treating stuttering, and many other disorders…

Single-Case Experimental Designs I want my A.B.A.!

Single-Case Experimental Designs Rather than using a control group, single-case experimental designs rely on a baseline stage. Baseline Stage - Behavior is recorded prior to any treatment. Example: Clinical researchers might measure how many times a target behavior (eye contact, shouting, swearing) occurs per minute, or hour, or week…

Single-Case Experimental Designs Behavioral Record From Baseline Stage

Single-Case Experimental Designs Once the central tendency and dispersion of the baseline stage become clear, the treatment can be introduced. The treatment can be introduced by way of an ABAB design, or a Multiple-Baseline Design (MBD)…. Let’s consider each in turn…

Single-Case Experimental Designs In an ABAB design, an initial baseline condition (A) is followed by a treatment stage (B), a return to baseline (A), and a return to treatment (B).

Single-Case Experimental Designs From Horton (1987). Behavior Modification. 11, 53-64.. Would someone please describe this study? http://www.ncbi.nlm.nih.gov/pubmed/3611388

Single-Case Experimental Designs Sometimes there is no reversal to baseline. Let’s consider 3 reasons why. Perhaps the new behavior reflects long term learning or skill acquisition. Perhaps the treatment was never causally related to the change in the first place. Perhaps the treatment was causally related to the change, but since that time, other factors are keeping behavior “in check”.

Single-Case Experimental Designs Sometimes the ABAB design can be unethical. Example: Head banging behavior in psychiatric patients can be debilitating. Do we really want the patient to return to baseline? The patient’s health can be more important than our intellectual curiosity about cause and effect.

Single-Case Experimental Designs If we don’t want behavior to return to baseline, we should avoid the ABAB design. In this case, the Multiple-Baseline Design (MBD) is an attractive alternative. There are several different variations on the multiple-baseline theme. First, we can have a multiple-baseline design across individuals…

Single-Case Experimental Designs From Allison & Ayllon, Journal of Applied Behavior Analysis, 1980. Single-Case Experimental Designs MBD across individuals: Football Body Blocks Would someone walk us through this?

Single-Case Experimental Designs Variation: Multiple-Baseline Design Across Behaviors: Children on the Autistic Spectrum http://www.ncbi.nlm.nih.gov/pubmed/?term=8926222 (a) Expressing Appreciation (b) Talking About Favorite Things (c) Expressing Sympathy (d) Expressing Dislike Variation: Multiple-Baseline Design Across Settings: A child’s aggressive behavior could be tracked… (a) In The Classroom (b) In The Lunch Room (c) On The Play Ground (d) In Supermarkets / Stores etc..

Single-Case Experimental Designs Because of the small sample sample size (typically N=1) single-case experiments can have low external validity. However, MBD with multiple individuals, or multiple situations, affords some generalizability. Also, it is difficult to show the interaction of multiple I.V.s using single-case experiments.

Skinner, (1956). American Psychologist, 11:221. Horton (1987). Behavior Modification. 11, 53-64 Allison & Ayllon, Journal of Applied Behavior Analysis, 1980.