1. Components of a causal relationship Does a change in X cause a change in Y? There are 3 components: 1) Co ‑ variation of events 2) Time ‑ order relationship 3) Elimination of alternative causes.

2. Independent Variable The presumed "cause" of a behavioral effect or change Manipulated (varied) by experimenter IV has several levels selected by experimenter Occurs, or can be "set up" before DV is measured "Independent" of what the subject does.

3. Dependent Variable Some measure of behavior that is a measure of the effect of the IV(cause) What is recorded by the experimenter The behavior occurs after IV is varied, and DV measures the behavior "Depends" on manipulation of the IV DV does not have levels.

4. Confounding Variable Any variable that is a potential cause for the experimental effect, other than the IV Any variable whose values change systematically across levels of the IV.

5. Control variable Variable whose values remain the same across levels of the IV (eg, room temp, light levels, time-of-day, etc).

6. Random variable Variable whose values vary randomly in an unbiased way across levels of the IV Random variables are usually created by the process of random assignment.

7. Subject variable A personal characteristic (eg, height, weight, gender, ethnicity, socio-economic status, etc).

8. Control group The group that receives “zero” or “the absence of” the IV Eg, the placebo group in a drug experiment The group that serves as a baseline to compare with the performances of the experimental groups.

9. Experimental groups The groups that receive non-zero values of the IV Eg, the drug groups in a drug study The performances of these groups are compared with the performance of the control group.

10. Conceptual Definition Definition of a variable at the conceptual or idea level Tends not to be very precise Tends to be more general, more vague.

11. Operational Definition Specifies the operations or procedures necessary to measure the variable Very precise Not general or vague at all Tells how the variable was measured There may be many OD’s for a single CD.

12. ODs and CDs - Example 1 Conceptual - Amount of alcohol Operational - # of beers in 1 hour (0,1,2,3) Operational - grams of alc./kg body weight Operational - BAC (mg alc./deciliter blood).

13. ODs and CDs - Example 2 Conceptual - Helping behavior Operational - # of people who help a “victim” Operational - duration of helping behavior Operational - # seconds before helping occurs (latency).

14. EXR-intermediate scenarios

15. Complex designs More than one IV Eg, Left/Right and 1, 5, or 10 spaces fr. center More efficient than single IV experiments Gives more information Allows analysis of main effects and interactions.

16. Complex designs - terminology An IV is called a factor number of numbers = how many IVs there are values of numbers = how many levels each IV has “2 X 2 design” (two IVs, each with 2 levels) “2 X 3 design” (first IV has 2 levels, second IV has 3 levels) “2 X 8 design” (first IV has 2 levels, second IV has 8 levels) “2 X 2 X 4 design” (first IV has 2 levels, second IV has 2 levels, third IV has 4 levels).

17. Main effects There is one potential main effect for each IV A 2 X 8 design has two possible main effects A 2 X 2 X 4 has three possible main effects A main effect is present if an IV had a significant effect on the experiment’s outcome (regardless of the effects of the other IVs).

18. Interactions Please memorize: “An interaction occurs if the effect of one IV varies depending on the level of the other IV”

19. EXR-horn honks and abstracts

20. Designing experiments Two general types of designs Between-subjects (between groups or independent groups) = each group gets one level of the IV Within-subjects (within-group or repeated measures) = each subject gets all levels of the IV Equivalency of groups at each level is built-in for within-subjects and achieved by random assignment for between-subjects Within - more efficient in terms of # of subjects Within - zero variability (ind diff) between levels.

21. Order effects Order effects (practice effects) = experiencing one level affects behavior in another level Eg, does content (biology text vs. novel) affect proofreading speed? Order is Biology-Novel Eg, practice, boredom, fatigue Order effects cannot occur in between-subjects and are controlled in within-subjects by randomization or counterbalancing.

22. Differential carryover effects (carryover effects, differential/asymmetrical transfer effects) The effect of the first level on the second level differs depending on which comes first Effect of B following A ≠ effect of A following B Confound is due to which level precedes which.

23. FIG: Order effects in proofreading Group 1 Biology 1 (no practice)(practice) Novel 2 Group 2 Biology 1 (no practice)(practice) Novel 2

24. FIG: Differential carryover effects in problem solving Group 1 Neutral instructions 1 (no practice)(practice) 2 Group 2 1 (no practice)(practice) 2 Special instructions Neutral instructions Special instructions

25. Other considerations Mixed designs (some between, some within) Small-n designs Matched groups designs Demand characteristics = cues that tell subjects how they should behave (eg, drug studies) Blind and double-blind procedures Internal and external validity Quasi experiments.

26. Group 1 Neutral instructions 1 (no practice)(practice) 2 Group 2 1 (no practice)(practice) 2 Special instructions Neutral instructions Special instructions