This document discusses key concepts in studying behavior including different types of variables, research methods, and validity. It outlines four categories of variables: situation, response, individual differences, and mediating. Experimental methods systematically manipulate and measure variables to establish causality by considering temporal order, covariation, and ruling out other explanations. While field studies have more external validity, experiments have greater control of extraneous variables. Validity includes external, internal, and construct validity. Statistical validity considers types of errors like false positives and negatives. Confounding third variables can obscure relationships and causality requires considering alternative explanations.

1. Studying Behavior

2. Variables vs. constants
• Measured variables
– Dependent
– Observed
• Manipulated variables
– Independent
– Controlled
• Four categories of variables

3. Research Variables
• There are four general categories of
variables.
– Situation variables
– Response variables
– Individual differences in participants variables
– Mediating variables

4. Mediating Variables
• Inferred psychological processes that are
often used to explain research outcomes.
– These variables are invented by the experimenter
and are related to the theory that produced the
experiment.
• Operational Definitions
– Measured variables must be defined clearly
4

5. Linear Relationship Graphs
Positive Negative
Association or Causal Claim?
Correlation

6. Curvilinear Relationship Graph
Non-monotonic No relationship

7. Nonexperimental Methods
• Causality MUST NOT be inferred from
correlational methods
– Causal direction
– The third-variable problem

8. • Experimental methods systematically
manipulate and measure variables.
• Causality must consider:
– Temporal order (precedence)
– Covariation between variables (cause and effect)
– Other explanations for the change must be
eliminated
Experimental Methods

9. Experimental vs Field Studies
• External validity
– Non-experimental field studies are more realistic
but extraneous variables are less controlled
• Ethical and practical concerns limit what
can be manipulated and controlled

10. Research Validity
• Valid: reasonable, accurate, and
justifiable
–External validity
• Generalizability
–Internal validity
• The extent of the relationship between two variables
–Construct validity
• How well the variables are measured or manipulated

11. Statistical Validity
VALID? REALITY:
YES
REALITY:
NO
TEST SAYS:
YES CORRECT
FALSE
POSITIVE
(TYPE I ERROR)
TEST SAYS:
NO
FALSE
NEGATIVE
(TYPE II ERROR)
CORRECT

12. Criteria for causation revisited
Research Methods in Psychology, 2nd Ed
by Beth Morling

13. Third variable revisited:
Confounding Variable
• Classic case: Violent crime and ice cream
sales
–Consider causal direction
• Violence leads to ice cream purchases
• Ice cream consumption leads to violence
–Missing anything?

14. Participant Variables
• Random Assignment
Research Methods in Psychology, 2nd Ed
by Beth Morling