Psychology: Brain, Mind,
and Culture, 2e
by
Drew Westen
Paul J. Wellman
Texas A&M University
John Wiley and Sons, Inc.
PowerPoint  Presentation: Chapter 2
Psychology: Research Methods in
Psychology
Lecture Outline
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Characteristics of Good Psychological
Research
Experimental Research
Descriptive Research
Correlational Research
Researching the Brain
Descriptive Statistics
© 1999 John Wiley and Sons, Inc.
Research Methods
 “Can mental events influence physical health?”
• Pennebaker study (1990)
– College students were asked to write for 20 min on 3
consecutive days on two topics:
» Emotional expression: “…your deepest thoughts”
» Control group: “what have you done since waking this
morning?”
– Pennebaker then measured visits to the campus health center
for subjects in both groups for months after the writing
exercises
» Results indicate that emotional expression subjects made
fewer visits to the health center
 Yes, emotional expression can improve health...
© 1999 John Wiley and Sons, Inc.
Characteristics of Good
Psychological Research
© 1999 John Wiley and Sons, Inc.
Research Concepts
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Psychologists are interested in determining
the causes of mental events and behaviors
• “What is the impact (effect) of divorce on children?”
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Issues in Theory:
• Systematic way of organizing observations
• Hypotheses are proposed relations between
variables (cause-effect relationships)
• Variable: Any phenomenon that can vary along
some dimension
– Continuous: varies continuously (body weight)
– Categorical: can take on fixed values (gender)
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Generalizability of Research
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Research studies take samples from a
limited portion of the entire population
(sampling must be representative).
Generalizability refers to whether your
research results can be applied to the
entire population of interest, and requires:
 Internal validity: Are the procedures of the
study sound or are they flawed?
 External validity: Does the experimental
situation resemble the situation found in the
real world?
© 1999 John Wiley and Sons, Inc.
Measurement Issues in Research
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Measure: A concrete means by which to
determine the value of a variable
• The variable “illness” can be defined as the
number of times that a subject visits a clinic
• The variable “hunger” can be defined in terms of
how long a subject has gone without food
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Measures of variables must be:
• Reliable: Produce consistent measurements
• Valid: Actually measure the variable of interest
© 1999 John Wiley and Sons, Inc.
Three Techniques to Determine
the Reliability of a Measure
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Test-retest reliability: Does the test give
similar values if the same subject takes it
two or more times?
Internal consistency: Different items that
measure the same variable should
produce similar answers.
Inter-rater reliability: Two testers that rate
the same person on the same variable
should give similar ratings to the subject
© 1999 John Wiley and Sons, Inc.
Issues in Validity
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Do the measures tap the appropriate
variable?
• Valid measures should allow for prediction of
behavior
– Measure of depression: Does it predict risk for suicide in
the future?
– Measure of intellect (IQ): Does it predict future school
performance?
• Validation research attempts to relate the measure
to an objective criterion
© 1999 John Wiley and Sons, Inc.
The Experimental Research Process
© 1999 John Wiley and Sons, Inc.
Defining Experiments
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Experiments ask whether systematic
variation in one variable produces
variation in another variable
• Independent variable (IV): Manipulated by
experimenter
• Dependent variable (DV): Participants response
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Example: Does exposure to THC increase
appetite?
• IV: THC dose (0 or 5 mg)
• DV: Amount of food consumed in 30 minutes
© 1999 John Wiley and Sons, Inc.
Issues in Experimental Research
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Control groups: A group that is similar to
the experimental group, except that it has
not been exposed to the treatment (i.e
given a placebo treatment rather than
THC)
Bias: Variation associated with subject
expectancies, experimenter expectancies
• Placebo treatments
• Double-blind studies
© 1999 John Wiley and Sons, Inc.
Limitations of Experimental
Research
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Complex real-world issues may not be
easily studied in the laboratory
Problems in external validity
The focus of experimental psychology is offbase: The interpretative stance suggests
that we should strive to understand the
personal meanings that govern behavior
rather than focus on predicting behavior
© 1999 John Wiley and Sons, Inc.
Descriptive Research
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The descriptive approach seeks to
describe phenomena rather than to
manipulate variables
Methods of descriptive research:
• Case studies
• Naturalistic observation
• Survey research
© 1999 John Wiley and Sons, Inc.
Case Studies
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An in-depth study of the behavior of one
person or a small group
• Used when large numbers of subjects are not
available
• Often used in clinical research
– Freud’s case study approach
• Drawbacks include
– Small sample size (limit to generalizability)
– Susceptibility to researcher bias
© 1999 John Wiley and Sons, Inc.
Naturalistic Observation
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In-depth study of a phenomenon in its
natural setting
• Examples include:
– Study of primate behavior in the wild
– Piaget’s study of the cognitive development of his
own children
• Advantage: Naturalistic studies have good
generalizability
• Disadvantages:
– Observation per se can alter behavior
– Observational technique cannot infer cause of
behavior
© 1999 John Wiley and Sons, Inc.
Survey Research
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Survey technique asks questions of
large numbers of persons to gain
information on attitudes and behavior
• Two approaches:
– Questionnaires
– Interviews
• Disadvantages of survey approach:
– Sampling issues
– People may not respond accurately
© 1999 John Wiley and Sons, Inc.
Correlational Research
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Aim of the correlational approach is to
determine the degree to which 2 or
more variables are related
Can determine association between
data from experiments, case studies, or
surveys
• Calculate the correlation coefficient (r)
– Values range from -1 through 0 through +1
– Negative correlations: High values of one variable
are associated with low values of the other variable
– Correlational studies do NOT establish causality
© 1999 John Wiley and Sons, Inc.
The Correlation Coefficient
© 1999 John Wiley and Sons, Inc.
Researching the Brain (Then)
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Research progress is dependent on the
technology available to investigators
• Early brain-behavior researchers were able to
examine the thoughts and behaviors of patients
who had suffered brain damage
– Broca noted that left hemisphere damage produced
a disorder of language
• Lesion experiments in animals: Create a lesion
within a discrete brain region and then examine
the effects of that lesion on behavior
– Hypothalamic damage can lead to obesity or
starvation, depending on the location of damage
© 1999 John Wiley and Sons, Inc.
Researching the Brain (Now)
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Brain imaging techniques allow us to look
for brain damage or to assess the activity
of discrete brain regions
 CAT and MRI scans produce a static picture of
brain structures
• MRI can be used to detect tumors
• Brain ventricle size: Large ventricles are
associated with brain damage
 PET scans: Radioactive tracers are used to
map brain regions for high and low activity
© 1999 John Wiley and Sons, Inc.
Brain Imaging: Ventricle Size in
Schizophrenia
Normal
Schizophrenic
Schizophrenic twin on right shows larger brain ventricles
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Issues in Evaluating Research
© 1999 John Wiley and Sons, Inc.
Descriptive Statistics
 Measurements of subject responses on a variable
are summarized using descriptive statistics:
• Frequency distribution of responses
• Histogram plots score range along x axis and score
frequency along y axis
© 1999 John Wiley and Sons, Inc.
Central Tendency and Variability
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Central tendency asks what the average
score is like in the distribution of scores
• Mean: Statistical average of all scores
• Median: The fiftieth percentile (half of the
scores are above this score, half are below)
• Mode: The most frequent score
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Variability asks how dispersed the
scores are relative to the average score
• Standard deviation: How far the average
participant score deviates from the average
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The Normal Distribution
© 1999 John Wiley and Sons, Inc.
Copyright
Copyright 1999 by John Wiley and Sons, New
York, NY. All rights reserved. No part of the
material protected by this copyright may be
reproduced or utilized in any form or by any means,
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© 1999 John Wiley and Sons, Inc.