Psych Lecture September 26th, 2013
• More research design
• The neuron
• Action potential
What are sources of bias in an experiment?
What is the basic structure of a neuron?
How do neurons “work”?
Next Time: The Synapse. Scan: 73-78
• Case study
o Between – groups design (more costly, but more effective)
Example: TV vs. aggression. Group 1 watches a violent show and then
measure aggression with that group. Group 2 watches non-violent show
and then measure aggression. Aggression = dependent variable because
it never changes. Violent show = independent variable because it is being
manipulated. Group 3 could be a control group to see how people act
before called “No treatment control”
o Within – groups design
Example: all subjects exposed to all conditions.
All watch violent show -> measure aggression. All watch non-violent show
-> measure aggression. Problem? Watching violent show first could spike
Potential order effect needs to be counterbalanced.
• Verbal attack
• Physical attack – shock test; able to shock the person who attacked you from low shock
to high shock.
• “safe” attack – bobo doll test
Threats to Validity
• Internal Validity
o Degree to which experiment supports casual conclusion (whether it was
confounded or not)
• External Validity
o Degree to which the results can be generalized (if you only test males, can’t put
results on females)
• Demand Characteristics
o Cues in experiment convey hypothesis to participants
o They “help” experimenter once they find out what the study is about
o Geen & Berkowitz (1967) – if you frustrate somebody and then allow them to
beat somebody up. If there is a weapon present in the room, people become
more aggressive by just seeing a weapon. • Experimenter Expectancy
o Experiments “conveys” hypothesis to participants. A subtle hint to participants
about what you’re expecting from the experiment.
o Intons-Peterson (1983) – being given a map and asking to give a distance.
Giving the participant the map to use during experiment, or having to imagine the
distance. Experimenter told them that perception would give better results, some
were told that being able to see the map would give them better results.
Whichever you were told you would do better in, the results showed they actually
did better in that one.
o Being able to eliminate this with double-blinded experiment.