Controlled investigations that study cause-effect
relations through the manipulation of variables.
Independent variable: What the experi-menter
manipulates to change or influence behavior.
Dependent variable: What the experimenter
measures.
Examples
Effects of television violence on aggressive
behavior in children.
One group of children watches an episode
of Xena.
Another group of children watches an episode
of Barney.
Later, children are allowed to play freely;
incidents of aggressive behavior are counted.
Examples
Effect of number of bystanders on willingness
of someone to seek help.
Each participant is placed in a room that
gradually starts to fill with smoke.
One group of participants placed in room with no other people.
Another group of participants placed in room with 3 other
people.
Measure the amount of time that passes before
the participant seeks help.
Issues in Experiments
Experimental vs. control groups
Confounding variables
Random assignment
Expectancy effects
Deception
Single-blind study
Double-blind study
External validity
Strengths & Weaknesses
+Precise control
+Strongest inferences about cause and effect
-Generalizability to individuals or real-world
situations may be limited
Questions about Example
What is the independent variable?
What is the dependent variable?
How could this experiment be improved?
Were experimental and control groups used?
Was assignment to groups random?
Can you think of any confounding variables?
Is expectancy likely to affect outcomes?
Ethics of Psychological Research
Informed Consent
People must be informed about any factors
that may affect their willingness to participate.
Deception is allowed only if it is necessary
and the scientific value is clear; deception may not cause harm
or affect willingness to participate.
Debriefing
Confidentiality
Ethics of Animal Research
Why use animals?
Experimental control (e.g., life span development)
Only way to study some phenomena (e.g., neurophysiology
of learning; neural plasticity)
Is animal research ethical?
Is animal research necessary?
Do animals suffer?
Summary
The major research methods used in psychology
are naturalistic observation, case studies, surveys, and experiments.
Each has advantages and disadvantages, but
experiments provide the best information about cause-effect relations.
Psychological research is governed by a strict
code of ethics that protects the well-being of human and animal
participants. All psychological research is approved by University
review committees ("IRB").