Research Techniques: Experiments

1. Research Techniques: Experiments

2. Research Techniques: Experiments Dependent Variable - measured Independent Variable – manipulated level = condition Darley and Gross (1983)

3. Research Techniques: Experiments • Advantages of Experiments • Control of extraneous factors

4. Semantic Priming Paradigm 2 words are presented, and participant responds to 2nd word prime - 1st word target - 2nd word

5. +

6. doctor

7. nurse

8. +

9. chair

10. nest

11. Semantic Priming Paradigm 2 words are presented, and participant responds to 2nd word prime - 1st word target - 2nd word primetargetreaction time doctor nurse 500 ms chair nest 525 ms Subject 1 Subject 2 related doctor – nurse unrelated chair – nurse unrelated chair – nest related bird - nest

12. Research Techniques: Experiments • Advantages of Experiments • Control of extraneous factors • Time efficient

13. Research Techniques: Experiments Critical Experiments – test contrasting predictions

14. Research Techniques: Experiments What-if Experiments – just to see what happens

15. Research Techniques: Experiments Replication direct replicate and extend

16. Research Techniques: Experiments Null Results (i.e., no effect of IV on DV) reasons 1. Hypothesis is wrong 2. Method is wrong - e.g., IV manipulation is weak IV = Amount of Candy Given levels = 1 M&M vs. 2 M&Ms

17. Research Techniques: Experiments Null Results reasons 1. Hypothesis is wrong 2. Method is wrong - e.g., IV manipulation is weak IV = Amount of Candy Given levels = 1 M&M vs. 2 M&Ms

18. Research Techniques: Experiments Null Results reasons 1. Hypothesis is wrong 2. Method is wrong - e.g., DV measure not sensitive vs.

19. Research Techniques: Experiments Control Variables – potential IVs held constant Ex. Examining the effect of sex on ratings of academic ability IV = sex of person to be rated (male, female) DV = rating (1-7 scale) Each participant reads two stories about two different people. Each story is accompanied by a picture of each person being rated. What do you control?

20. Independent variables are manipulated Dependent variables are measured Control variables are held constant

21. A college student wants to examine the effects of sleep and caffeine intake on memory performance. He selects 80 people and randomly assigns them to one of the following groups: 1) 2 cups of coffee, much sleep 2) 2 cups of coffee, little sleep 3) no coffee, much sleep 4) no coffee, little sleep The much-sleep group agrees to try to get as much a sleep as possible, and the little-sleep group agrees to sleep for no more than 4.5 hours a night. The coffee groups drink two cups of coffee prior to testing, and the no-coffee groups abstain from coffee for one week prior to testing. Recall performance on 5 lists of words is obtained. Questions: 1. What are the independent variables and dependent variables? 2. What factors should be controlled?

22. More than 1 independent variable Advantages more efficient (i.e., can look at several IVs at once) easier to control (e.g., time of day, time of semester) more powerful (i.e., error variance is decreased) results that generalize across IVs are valuable (e.g., social loafing) can look for interactions b/w variables

23. More than 1 independent variable Example 1 – McRae et al. (1995) IVs Type of Video (makeup, chopsticks, control) Trait Stereotype (woman, Chinese) DV = Decision Latencies example words: emotional gracious

24. More than 1 independent variable Example 2 – Fallon and Rozin (1985)

25. Fallon & Rozin (1985) Males and females rated figures on: a) current state b) ideal state c) most attractive IV Type of Rating (current, ideal, most attractive) Subject Variable Sex of Participant (male, female) DV - rating

26. Fallon & Rozin (1985) Results (interaction b/w sex and type of rating) Men current = ideal = most attractive Women current> most attractive> ideal

28. More than 1 dependent variable Behavior = rat pressing a bar Potential DVs number of bar presses force of bar press(es) latency of bar press Stats - either analyze together or separately

29. Abrams and Balota, 1991

30. Experimental Designs Between-subjects Within-subjects Mixed

31. Experimental Designs -e.g., type of therapy (traditional, cognitive) Between-subjects equivalent groups matching randomization

32. Experimental Designs Within-subjects general practice effects fatigue boredom counterbalancing differential carryover effects

33. Differential Carryover Effects DRM Experiment w/ warning manipulation IV – Warning Status (unwarned, warned)

34. Differential Carryover Effects – when the outcome depends on the order of conditions DRM Experiment w/ warning manipulation

35. Experimental Designs - e.g., word length (short, long) Within-subjects general practice effects fatigue boredom counterbalancing differential carryover effects small-n design Prins & Mussap (2001)

36. Experimental Designs Mixed – type of therapy (traditional, cognitive) time of test (pre-, post-)

37. Demand Characteristics Cues that participants perceive as indicators of the purpose of the experiment

38. Experimenter Effect Cues that provide info about what the experimenter expects Double-blind experiment Drug vs. placebo

39. Quasi-experiments Subject variables

40. Quasi-experiments Subject variables - age

41. Quasi-experiments Subject variables – age and dementia status Balota, Cortese, Duchek, Adams, Roediger, McDermott, & Yerys (1999)

42. Quasi-experiments Subject variables - sex

43. Fallon & Rozin (1985) Results (interaction b/w sex and type of rating) Men current = ideal = most attractive Women current> most attractive> ideal

44. Quasi-experiments Subject variables – Memory Span

45. Individual Differences in Working Memory Memory Span Test (Daneman & Carpenter, 1980) Sentence 1 – last word Sentence 2 – last word etc. - test memory for last words e.g., We were fifty miles out at sea before we lost sight of land. The city had grown to be the largest city in the state. It is a wonder that you can remember your own name.

46. Individual Differences in Working Memory Low vs. High Span – Noun Reference (Daneman & Carpenter, 1980) The boy saw an injured dog. Dinner time was approaching. The boy needed to be home by 6:00 PM. The boy picked it up. The boy saw an injured dog. Dinner time was approaching. The boy needed to be home by 6:00 PM. After dinner, the family would play cards. Hearts was his favorite card game. He also liked poker. The boy picked it up.

47. Individual Differences in Working Memory Low vs. High Span – Noun Reference (Daneman & Carpenter, 1980)

48. Quasi-experiments Matching – deliberate equating of groups Example: Age Young vs. Old education vocabulary ability vision hearing memory etc.

49. Quasi-experiments Regression to the mean (i.e., regression artifacts) Extreme scores on one testing occasion are likely to be less extreme on a second testing occasion

50. Quasi-experiments Regression to the mean (i.e., regression artifacts) Extreme scores on one testing occasion are likely to be less extreme on a second testing occasion Example: At Risk Drinkers - College Freshman Goal: to identify (based on personality test) at riskers, and introduce intervention to reduce drinking behavior