1. Experimental Design 3: Demand Characteristics Martin Ch. 4

2. Demand Characteristics n Definition: –Clues given to the participant about the point of the experiment n Examples: –Experiment title: The effects of horror movies on mood –Obvious manipulation: Ten psychology students looking straight up –Biased or leading questions: Don’t you think it’s bad to murder unborn children?

3. Reactions to Demand Characteristics n Cooperative –“You seem like a nice person: I’ll help you get the right results” n Defensive –“I don’t want to look stupid/evil. I’ll do what a smart/good person is expected to do (rather than what I normally would do).” n Noncooperative –“This experiment is annoying. Let me screw up the results.”

4. Sources of Demand Characteristic Effects n Societal values –Be cooperative, look smart, … n Experimenter expectancies –Consciously or unconsciously suggesting what outcomes are desired n Negative feelings about being in the experiment –Maybe as a result of previous bad experiences

5. How to Test for the Effects of Demand Characteristics n Both positive + negative test questions n Include other tests of social compliance –See if these tests relate to performance n Post-experiment debriefing n Placebo control

6. Placebo n What makes a good placebo? –Keep all the details the same, especially things the subject is likely to develop expectations about n When does the placebo effect work? –Cognitively penetrable processes

7. How to Minimize Demand Characteristics n Automation n Blind and double-blind n Multiple experimenters n Naturalistic observation n Neutral test questions

8. Demand Characteristics Example: Mental scanning rates n Cognitive penetrability

9. Experiment validity examples n Course evaluation –Use course evaluation forms to see which version of a class is better n Evaluation of effective student behaviors –Use essay test scores and questionnaire to see which studying behaviors lead to better learning