Small-N and Single-subject Designs

1. Small-N and Single-subject Designs Susan Varni Fall 2002

2. Small-N and Single-subject DesignsWhere are we going? • Why Small-N Designs? • History of Small-N in Psychology • Variations on a Theme • Psychophysics

3. Why Are You Studying Psychology? • Take 2 minutes to write down why you are studying psychology. • What about psychology interests you? • What topics? • What profession do you aspire to? • What impassions you about psychology? • What do you hope to do with the knowledge that you gain here?

4. Small-N Designs • Definition • Studies that use “several” participants with data that is individually described and may or may not be statistically analyzed

5. Pros of Small-N • Avoiding problems with the group mean* • Can examine participants from hard to find populations* • *Key reasons currently! • Following are both current & historical reasons • Can deal explicitly with individual (not group) behavior • Results are easy to interpret (often no stats!) • Avoids small, unimportant effects • Flexibility • Can focus on helping one (few) participant

6. Cons of Small-N • Hard to demonstrate causality • No controls in most cases • Lack of statistics • (Major “significance test” is the IOT) • Can’t really look at interaction effects • Counterbalancing is a problem • DV usually limited to response rates • Problem of external validity

7. History of Psychology and Small-N Designs • Psychology really began with small-n • Ebbinghaus-nonsense syllables • Darwin-child development • Watson and Raynor-Little Albert

8. History of Psychology and Small-N Designs • Wilhelm Wundt (1832-1920) • Leipzig Laboratory • “E” was the “S” and others were “replications”

9. History of Psychology and Small-N Designs • Edward Thorndike (1874-1949) • Animal Learning “I then suggested [to James] experiments with the instinctive and intelligent behavior of chicken as a topic, and this was accepted. I kept these animals and conducted the experiments in my room until the landlady’s protests were imperative. James tried to get the few square feet required for me in the laboratory…He was refused and with his habitual kindness and devotion to underdogs and eccentric aspects of science, harbored my chickens in the cellar of his own home for the rest of the year” (Thorndike, 1936 as quoted in Hothersall, 1995) • Cats and Puzzle Boxes (results for every cat)

10. History of Psychology and Small-N Designs • B.F. Skinner • Operant Conditioning • Why are we considering this among small-n designs?

11. Designs • Three Essential Elements • Operational definitions • Baselines (A) • Treatment (and continued monitoring) (B)

12. Baseline Designs • Once baseline has been maintained, it is unlikely that a confounding event will affect results on the same trial as the manipulation • Design (A = baseline, B = treatment) A B { O1 X/O2 }

13. Phantom Pain (A-B) • Jonsson & Fisher, 1996 • Phantom pain is hard to treat (don’t really understand it) and methods have been inconsistent • Hard to find participants • Studied one woman who has had both legs amputated • Treated pain control by attention diversion

14. Phantom Limb Results

15. Withdrawal Designs • It is unlikely that a confound will cease to affect the results on the same trial the manipulation is removed • It is more unlikely that a confound will re-affect the results on the same trial the manipulation is re-introduced

16. Withdrawal Designs • Design (A = baseline, B = treatment) 1. A B A 2. A B A B 3. A B A C

17. Cocaine Abstinence (A-B-A) • Silverman, Wong et al., 1998 • Methods of keeping people in a methodone treatment program from using cocaine • Used escalating reinforcement for cocaine-free urine samples ($2.50 for first, add $2.96 for each additional) (could get up to $1950 over the course of the study) • Baseline, reinforcement, then removed reinforcement

18. Results

19. Condom Taking (A-B-A-B) • Kirby et al., 1998 • Drug abusers are at high-risk for HIV • Would prompting cocaine users result in their taking (and hopefully using) more condoms? • Treatment: After counseling, clients were informed of risk and encouraged to take condoms

20. Results

21. Conversion Disorder (A-B-(A)-C) • Donahue, Thevenin, & Runyon, 1997 • Conversion disorder: physical symptoms (often following stressor) without organic cause • 12-year old girl complained of throat constriction (following choking on food) • Treated with (B) training meals (positive thoughts while eating), and then with (C) reinforcement (call brother, eat w/TV)

22. Results B C

23. Multiple Baseline Designs • If treatment start time is staggered, it is unlikely a single confound can explain all perceived treatment effects • 3 Types • Same behavior in 2 or more individuals • 2 or more different behaviors within the same individual • Same behavior within the same individual but in 2 or more different settings

24. Other Designs Mentioned in the Text • Changing criterion design (“shaping”) • A - B - C - B, where C is non-contingent reinf. • A - A1 - B - A1 - B (A1 a placebo for B) • Alternating treatments • A-B-A-C-A-D-A • A-D-A-C-A-B-A, etc.

25. And now for something completely different… • Although, not really different • Exercise • Melody Lateralization • Chromatic and luminance modulation

26. Psychophysics • Fechner, October 22, 1850  Elements of Psychophysics (1860) • Profound insight about relation of physical stimuli () to their mental representations () • Concepts: • Absolute threshold (min. energy to detect) • Difference threshold (min. energy to notice change) • Methods (limits, constant stimuli, adjustment) are still in use • Newer -- signal detection theory (SDT) separates our sensitivity to stimuli from individual criteria for saying “yes” or “no”