Psychology
The Scientific Study of Mind and
Behavior
Introduction and Methods
Psychology as Science
Scientific Method
1. Systematically observe some phenomenon or aspect of the
universe
2. Construct a falsifiable theory (description of structures, models,
processes) that is consistent with what you have observed and
seems to describe or account for how the phenomenon works
3. Use the theory to make predictions
4. Test those predictions by experiments or further observations
5. Modify the theory in the light of your results
6. Go to step 3
Falsifiable Scientific Theories?
2+2=4
Theory:
Not falsifiable
Learning is always the result of reinforcement.
Not falsifiable as stated
Definitions:
Learning: Any change in the probability of a
behavior occurring
Reinforcer: Anything that changes the probability of
a behavior occurring
Methods of Systematic Observation
Randomized or ‘True’ Experiment
Quasi-Experiment or ‘Correlational Study’
Case Study
Naturalistic Observation
Computer Simulation Study
Randomized or ‘True’ Experiment
Two major characteristics
Controlled manipulation of an independent variable
Random assignment of subjects to conditions
Some definitions
Independent variable
The variable the researcher manipulates. It is often a discrete
(qualitative) variable with levels that are the different conditions
Dependent variable
The variable that the researcher measures. It is called a dependent
variable because it depends upon (is caused by) the independent
variable. It is often a continuous quantitative variable
Operational definition
The operational definition of a variable specifies precisely the
process whereby the variable is measured or manipulated
Schacter’s (1959) Well Known Experiment Examining
The Relation Between Fear And Affiliation
Schacter was interested in whether subjects who are experiencing
more anxiety or fear have a stronger desire to affiliate with other
people than subjects experiencing lower levels of fear
Subjects were randomly assigned to be in either a ‘High Fear’
condition or a ‘Low Fear’ condition
High Fear Condition
Told that the experiment would require them to receive intense, painful
(but not permanently damaging) electric shocks
Low Fear Condition
Told that the experiment they were in would require them to receive
mild and painless electric shocks
Both groups were told that the experimenter needed another ten
minutes to prepare the equipment, but that the subject could wait
either alone in a room with armchairs and magazines or in
classroom with other subjects
Subject was asked to choose whether to wait alone or with others
Results
Together Don't Care
High Fear
63%
28%
Low Fear
33%
60%
Alone
9%
7%
Quasi-Experiment or 'Correlational
Study'
No random assignment or manipulation of
an independent variable
Experimenter simply observes values of
the variables in the study
Example Illustrating Distinction Between
Randomized and Quasi-experiments
Consider two studies of diastolic blood pressure that found exactly
the same data, but had different designs as illustrated in the
table
Dosage of Vitamin E
Mean
Placebo
200 IUs/day
IUs/day
400 IUs/day
IUs/day
0 UIs/day
200 IUs/day
IUs/day
400 IUs/day
IUs/day
95
91
73
79
72
81
100
86
66
85
80
81
96
85
63
91
75
60
82
90
75
100
69
77
91
81
72
Experiment
Quasi-experiment
How do the interpretations of the results in the
randomized experiment and the quasiexperiment differ?
What does random assignment do for
you?
Allows us to conclude that vitamin E dosage
differences caused the differences in diastolic
pressure
In the quasi-experiment one is not entitled
to draw the strong causal inference
We can only conclude that there is an
association between vitamin E intake and
diastolic pressure
Case Study
Extensive and intensive examination of a single
subject or case
Example: Phineas Gage
Naturalistic Observation
Systematic observation of subjects in their
natural setting
Example: Jane Goodall’s work studying
chimpanzees in Gombe National Park in
Tanzania
Computer Simulation Study
Simulation of observed behavioral
processes using a computer model
Example: Neural network models of
memory processes in the brain