Thinking Too Much Impairs Decision-Making

1. Participant Recruitment

1. Conduct a power analysis and recruit a sufficient number of participants and obtain informed consent from the participants.
2. Gather two experimenters: One to administer the jam taste test, and another (blind to condition) to obtain participants’ ratings of each jam.
3. Recruit volunteers for a study entitled "Jam Taste Test". Instruct volunteer subjects not to eat anything for 3 hrs prior to the study.

2. Data Collection

1. Purchase five brands of strawberry jams or preserves that vary in their overall quality.
   1. To provide participants with a large range of jam quality, the original researchers purchased the 1^st-, 11^th-, 24^th-, 32^nd-, and 44^th-ranking jams in a report produced by Consumer Reports magazine of 45 different jam brands (“Strawberry Jams," 1985). This report contained expert rankings based on the ratings of seven consultants who were trained sensory panelists. Each expert consultant rated 45 jams across 16 specific sensory characteristics, such as sweetness, aroma, etc. Averages were calculated across all seven expert consultants’ ratings to yield rankings of all 45 jams.
2. Prior to running each participant, set up the testing room. You’ll need a table, a chair, plates, spoons, jams, labels, and a trash can.
3. Arrange the five jams in a random on the table, labeled A through E.
4. Keep track of which jam receives which label for each participant, and in which order the jams are arranged.
5. Take one teaspoon of Jam A and place that spoonful on a plate in front of the Jam A jar.
6. Repeat for Jams B through E.
7. Run participants individually.
8. Have Experimenter 1 inform each participant that the purpose of the study is to evaluate different kinds of jams under different conditions, as part of a consumer psychology experiment.
   1. Explain that some participants will taste jams on crackers, while others will taste jams on plastic spoons.
   2. Critically, inform the participant that they have been randomly assigned to the condition in which they’ll be tasting jams on spoons. Specifically, after tasting the jams, they will rate their liking for each one.
9. Have each participant sign a consent form, giving their informed consent to participate.
10. Randomly assign participants to either the “reasons-analysis” condition, or a control condition.
    1. Provide “reasons-analysis” participants with written instructions asking them to "analyze why you feel the way you do about each" jam," in order to prepare yourself for your evaluations."
    2. Inform these participants that they will be asked to list their reasons for liking or disliking each jam after tasting. Describe this task as a means of organizing participants’ thoughts prior to rating, and further, inform participants that they will not be asked to hand in their list of reasons.
    3. Do not give the rest of participants (e.g., control participants) any additional instructions.
11. Ask participants to be seated at the table where the five jams have been arranged spoons with approximately 1 tsp of strawberry jam.
12. For “reasons-analysis” participants, have Experimenter 1 ask the participants to taste each of the five jams.
    1. During the tasting, leave the room.
    2. Upon returning, administer the reasons questionnaire. This questionnaire should ask participants to list their reasons for liking or disliking each of the Jams A through E.
    3. Reiterate that the purpose of the questionnaire is to organize the subjects' thoughts and that they would not be asked to hand it in.
    4. Leave the room once again.
    5. Upon returning, explain that the completed questionnaire will no longer be needed, and should put the questionnaire in the trash can.
13. For control participants, have Experimenter 1 also ask the participants to taste each of the five jams.
    1. During tasting, leave the room.
    2. Upon returning, administer a filler questionnaire instructing participants to list reasons why they chose their major.
    3. Leave the room once again.
    4. Upon returning, collect the completed filler questionnaire.
14. Have Experimenter 1 now introduce the participant to Experimenter 2, who must be unaware of the condition that the participant was assigned to.
15. Have Experimenter 2 administer a questionnaire to the participant asking them to evaluate each of the jams on a 9-point scale ranging from disliked (1) to liked (9).
16. Instruct participants to complete the questionnaire and to place it through a slot in a covered box on the table, to maintain anonymity.
17. Leave the room while participants are completing this questionnaire.
18. Upon returning, fully debrief the participant regarding the purpose and procedures of the study.

3. Data Analysis

1. After running all participants, test whether evaluations of the jams varied between participants in the “reasons-analysis” condition (e.g., those who analyzed how they felt about the jams) and those in the control condition (e.g., those who did not) via a 2 (condition: reasons analysis vs. control) x 5 (jams 1, 2, 3, 4, and 5) multivariate ANOVA.
2. To compare the degree of agreement with expert ratings between participants in the “reasons-analysis” condition and those in the control condition, simply compute the Spearman’s rank-order correlation between each participant’s subjective ratings of each jam and the expert ratings of each jam, on a subject-by-subject basis.
   1. Convert these values to z-scores via Fisher’s r-to-z transformation for purposes of analyses.
   2. Perform an independent-samples t-test examining how the average participant/expert correlation varies as a function of group.
   3.  Use two, one-sample t-tests comparing the average participant/expert correlation in the “reasons-analysis” condition and the control condition against zero separately.