Understanding Mediation Analysis: History, Function, Utility, and Character

1. MEDIATION 1. History: S  R explanations do not address full range of psychological phenomena. In many cases, SOR makes more sense. 2. Function: Mediational analyses designed to test for SOR causal paths. 3. Mediation Defined: “the effects of stimuli on behavior are mediated by various transformations internal to the organism.” 4. Utility: Mediators directly explain why events occur (but can also provide clues to how and when they occur). 5. Character: Mediators are latent variables, or latent constructs.

2. Attributes of Mediators Mediator 1. IV predicts DV 2. Changes in IV account for changes in mediator 3. Changes in mediator account for changes in DV. 4. When links between IV to Mediator, and between Mediator to DV are established, the link between IV and DV becomes non-significant, or becomes significantly decreased IV DV Immuno- compromise Stress Illness

3. Mediational Model Mediator a b c DV IV When Mediation is present: r (a) is significant r (b) is significant r (c), which was significant before the mediator was included, is either not significant or is much weaker after mediator is included.

4. Self-Image Concerns a b c Positive Bias Race of Recipient Mediational Model and Feedback Studies IV? Race of recipient DV? Positive bias Self-image concerns Mediator? No. "b" must also be sig, AND... "a" is significant. Mediation shown? When "a" and "b" considered, "c" no longer significant. What shows mediation here?

5. MODERATOR DEFINED, Cont. Moderator is always an Independent Variable Moderator should be un-correlated to DV Moderators sought when there is weak or inconsistent relationship between IV and DV. Moderator confirmed only if interaction between moderator and main IV is significant F [mud * Temp] = 8.54, p < .05. ST M Why a problem? MemMud does seem to work, even if mainly on those with better LTM. STM = Short Term Memory LTM = Long Term Memory

6. Problem when Moderator Correlates to DV Sleep Hours Anxiety // Sleep very highly correlated r = .70, p < .001 Why is this a problem? Is better sleep due to med or due to placebo effect?

7. RELATION BETWEEN MODERATORS AND MEDIATORS Scary Movie Scary Movie Moderator to mediator: Knowing how external variables affect outcomes can imply the existence of mediators. Mediator to Moderator: Knowing why underlying mechanism affects outcomes can suggest ways of inducing, remedying, or altering the outcome. Fear Exercise Movie X Exercise Pos. Mediator: Physio. Arousal Physio. Arousal Fear Scary Movie Pos. Moderator: Exercise

8. Why Do People Need Self Esteem? Converging Evidence that Self Esteem Provides an Anxiety-Buffering Function Greenberg, et al., 2000 Studies assessed the proposition that self-esteem serves an anxiety-buffering function. In Study 1, it was hypothesized that raising self-esteem would reduce anxiety in response to vivid images of death or neutral images. In support of this hypothesis, subjects who received positive personality feedback reported less anxiety in response to a video about death than did neutral feedback subjects. X ____Moderator ____Mediator

9. Greenberg, et al. 2000 Scary Images + Self Esteem 0 Anxiety +++ Scary Images X Self Esteem

10. Anxiety as a Function of Threat Salience and Level of Self Esteem Greenberg, et al., 2000

11. Visceral Perception and Nonconscious Fear Conditioning Katkin, Wiens, & Öhman, 2001 Previous research shows that people conditioned to fear certain kinds of stimuli such as snakes or spiders are subsequently better able to detect hidden images of these stimuli compared to people who are not conditioned. The current research predicts that this heightened sensitivity is restricted to people who are good at detecting their own heartbeats (good heartbeat monitors). This prediction was confirmed; when good heartbeat monitors are excluded from analysis the effect of fear conditioning on stimuli sensitivity disappears. [ABSTRACT MODIFIED ] X ____Moderator ____Mediator

12. Katkin, Wiens, & Öhman, 2001 Heartbeat Monitors a b c Stimuli Sensitivity Conditioned Fear

13. Path Analyses and Causal Models • Attend. in 21st Century program  improved performance by minority students. • 21st Century program based on theory of stereotype-threat. When threat is high, minority students do less well. • Stereotype threat is itself a problem because it causes minority students to disidentify with academics. What is the causal model? What would be strong and weak correlational links in this model?

14. First Semester Grades as Predicted by Stereotype Threat, Identification with School, and Participation in 21st Century Program ID with School Stereo. Threat 21st Cent. Prog. Grades Task: What are IVs, DVs? What are moderators (if any)? What mediators (if any)? Put these in correct path Estimate relations between variables, outcome

15. 21st Century Program, Stereotype Threat, and Identification with School

16. Ultimate Mediation? The Epistemological Challenge of Science  Multiple underlying causes: Disclosure --> Emotional resolution --> less stress --> immune boost --> health Race of recipient --> egalitarian concerns --> self-image concerns --> bias Ultimate underlying causes: Disclosure ---> coping (Pennebaker, 1989) Disclosure --> [????] --> coping Disclosure --> self-affirmation --> coping (Cresswell, et al., 2007) Disclosure --> self-affirmation --> [????] --> coping Is this issue same as Popper’s “infinite regress” problem? Not sure . Regress might be, e.g., what makes up “coping”. Ultimate mediation is locating the complete causal chain.

19. Independent Variables Class 08

20. IV: Conceptual vs. Experimental Conceptual IV: General class of causes relevant to underlying theory. Examples: “Insult”, “Fear”, “Perceived Control” Experimental IV: Specific operations used to represent the conceptual IV. Examples: “Bumped and sworn at by confed”, handling a live snake, given “stop button” to stop stressful event.

21. Independent Variable: Conceptual and Empirical Forms Conceptual IV Empirical Realization Race of essay writer Writer’s Description Sheet Poorly executed performance Poorly written essay Experimenter saying “give shocks” Authority commanding obedience Demeaning clothes, ankle chains, numbers rather than names. Prisoner experience Ethical dilemma Fate of Ghakistani boy

22. Experimental IV, continued Experimental IV typically of no theoretical value However, Expt’l IV can be of great PRACTICAL value. 1. “Stop button” on pain manipulation affects pain tolerance: Practical Value? 2. Writing thoughts and feelings reduces hostility: Practical Value? Subset of IVs that can be of both conceptual and experimental: 1. Demographics: Gender, race, nationality 2. Personality: Attachment style, self-esteem, etc.

23. Goals in Designing IV Select IV that represents conceptual IV 1. Good IV is a good metaphor (Hurry to talk on Good Samaritan before encountering stranger in need.) 2. But, may also have direct practical value (Consider own virtues before dealing with threat) Present IV in a way that maximizes effect 1. For subjects a. To induce interest (e.g. “you will receive shocks.”) b. To keep true purpose of study hidden from Ss 2. For outside audience: Want to tell good story (“holding spouses hand, experimenter’s hand… “)

24. Instructions Form of IV Written, verbal info. that conveys the IV Advantage: 1. High control 2. Work with populations un-suited for event manipulations 3. Convenience, ease of use, economical Success depends upon: 1. Commanding Attention 2. Comprehension of instructions a. Keep design simple b. Keep language simple

25. Loss Condition Gain Condition If Program A is adopted, 400 people will die. If Program A is adopted, 200 people will live. If Program B is adopted, there is a one-third probability that nobody will die and a two-thirds probability that 600 people will die. If Program B is adopted, there is a one-third probability that 600 people will be saved, and a two-thirds probability that no people will be saved. Prospect Theory: Kahneman & Tversky, 1984 Demonstration of "Instructions" IV) Newark is preparing for the outbreak of an unusual air-borne disease, which is expected to kill 600 people. Two alternative programs are available to combat the disease, but they cannot be used simultaneously. Which do you choose? I pick: ____ Program A ____ Program B

26. Loss Condition Gain Condition If Program A is adopted, 400 people will die. If Program A is adopted, 200 people will live. If Program B is adopted, there is a one-third probability that nobody will die and a two-thirds probability that 600 people will die. If Program B is adopted, there is a one-third probability that 600 people will be saved, and a two-thirds probability that no people will be saved. Prospect Theory: Kahneman & Tversky, 1984 Demonstration of "Instructions" IV) Newark is preparing for the outbreak of an unusual air-borne disease, which is expected to kill up to 600 people. Two alternative programs are available to combat the disease, but they cannot be used simultaneously. Which do you choose? I pick: ____ Program A ____ Program B

27. Vignette as Within-Subjects Manipulation Adapted from Adler-Russell, 1983 Situation 1: Officer Clements is a third year patrol officer. HE/SHE responded to a domestic violence report, found husband threatening his wife due to over-draft. Officer Clements first confirmed that the wife was not injured nor feared injury, and informed her of protections and rights. Officer Clements then told husband, in front of wife, that further threats may lead to arrest. How effectively did Clements respond to this situation? Situation 2: Officer Williams is a third years patrol officer. HE/SHE responded to an armed robbery at a local convenience store. HE/SHE saw suspect waving a pistol at the clerk, while backing out of store. Officer Williams waited until suspect cleared the doorway and the clerk was out of danger. However, this provided suspect an opportunity to flee, and suspect is still at large. How effectively did Clements respond to this situation?

28. Tuning in to IV Inductions • Group 1 • When Kent says “GO” stand and actually sing happy birthday in highest octave possible. • First rate pre-singing discomfort, 1 – 7: • = No discomfort • = Extreme discomfort • After singing, you will re-rate discomfort • Group 2 • When Kent says “GO” imagine you had to sign happy birthday in highest octave possible • First rate pre-imagining discomfort, 1 – 7: • = No discomfort • = Extreme discomfort • After imagining, you will re-rate discomfort

29. Problems with Instructions Forms of IV 1. Lack external validity (e.g., Kahneman & Tversky) 2. Too abstracted (Joshua Greene moral choices) 3. Enlists subjects from the neck up

30. Event Form of IV Event: Actual situation that conveys the conceptual IV Advantages 1. Absorbing 2. Can approximate real world IV 3. Tell a more compelling story Problems 1. Not clear it exclusively conveys IV 2. Not easy to standardize 3. Not economical, difficult to run

31. Common Forms of Event IV 1. Accident, unplanned occurrence a. Smoke from vent b. Person collapses in next room 2. Confederate a. Culture of Honor (Cohen & Nisbett) 3. Whole experiment as manipulation (ethical problems here) a. “Failed” egalitarian, then meet panhandler (Dutton & Lake) 4. Experiment w/n experiment a . Self affirmation and lab coat (Steele) 5. Real world events: War of Worlds, Y2K, Gulf War I, Movies, etc.

33. Standardization: Procedural and Psychological Stimulus Event  This is event we can standardize Stimulus Perception  This is event we ultimately want to standardize, but can’t directly control Response This is event intended to reflect only intended stimulus, and not any unintended stimulus.

34. Standardization: Procedural and Psychological Stimulus Perception  Stimulus Event  Response

35. Standardization of IV Goal: All subjects experience the IV in the same way. Procedural standardization: Standardize IV as given by E Flexibility in IV presentation: Standardize IV as experienced by S Problems with flexibility? Eine kleine “knock-knock” music

36. Pilot Testing of IV Purpose: ID problems before experiment begins 1. Power of manipulation 2. Clarity: Alternative interpretations? 3. Presentation a. Believable? b. Production value? 4. Artifacts: Expt'l IV introduces unintended stimuli 5. Ways to bolster IV

37. Methods of Piloting 1. Interview subjects a. Subs are great info source b. Highly motivated to help c. Probe immediately after IV, NOT at end of study (WHY?) d. Problems with interviewing? 2. Test against objective criterion a. Stress manipulation – bio measures b. Use experts: Feedback task, professional tutors

38. Pilot Testing Using Objective Criteria Prediction: Distress will lead urbanites, but not rural folk, to disclose personal feelings. Conceptual IV: Distress Empirical Realization of IV: Disturbing movie (e.g., Titanic sinks) Pilot Test Goal: Is movie upsetting? Post-Expt. Interviews: Limited value; if prediction is true, rural folk might not provide reliable info. Objective Criteria: Non-verbal reactions (HR, GSR)

39. Internal Analysis Purpose: To find out why experiment didn't work Tools: a. Manipulation Checks b. Post hoc data analyses Limits to conclusions from internal analyses Internal analyses valuable even when experiments "work"

42. Subliminal Priming: Special Class of IV Purpose: Short cut to psyche; direct path into black box * Get past conscious editor * Activate otherwise inaccessible mental processes Nature: Exist between “instruction” and “event” manipulations. Examples: * “Mommy and I are one”: Silverstein  lower psych. symptoms Improve learning * Happy/sad faces: Winkielman  Ratings of Kool-aid  Consumption of Kool-aid