PSY100 – Personality
• Approaches to the Scientific Study of
Personality
• Describing and Measuring Individual
Differences
• Validating Individual Difference Measures
• Important Consequences of Individual
Differences
• Causes of Individual Differences
How does Personality Psychology differ from
Other Disciplines in Psychology?
• Cognitive psychology: The science of basic
cognitive processes
• Neuropsychology: The science of the
connection between the brain and the mind
• Social psychology: The science of social
influences on psychological processes
• Developmental psychology: The science of
changes in psychological processes over the life
span.
• All these disciplines implicitly assume that all
people are the same.
• Personality psychology makes a different
assumption: People are different from one another
in important ways.
• Cognitive “Why do some people have better
memories than others?”
• Social “Why do people respond differently to
rejection by others?”
• Developmental “Why are some children more
afraid of strangers than others?”
Two Approaches to Personality:
Idiographic versus Nomothetic Approach
The idiographic (person-centered) approach:
A focus on one individual at a time, and it tries to
understand this individuals’ actions from the
individuals’ characteristics.
The nomothetic (variable-centered) approach
A focus on the relation between a certain outcome
such as academic achievement (getting an A in this
class) to a variable like organized-disorganized.
Idiographic
Nomothetic
Traditional
Grand Theories
One individual at a time
Qualitative
Freud
Modern
Small Theories
Large samples
Quantitative
Eysenck
Idiographic question: Why did Mariah Carey
have a nervous breakdown?
Nomothetic question: Are young stars in the
music industry more likely to suffer a nervous
breakdown than normal people?
• Freud & Rogers – It is impossible to test
scientific theories with case studies.
• Skinner – Behaviorism assumed that all
people are born equal and that individual
differences are a mere consequence of different
learning experiences. Nobody believes this
anymore.
• Eysenck – An influential early proponent of
the nomothetic approach. Although
unnecessarily confrontational, his work
continues to influence modern personality
research.
Important Notice
• As noted in the textbook, “in recent decades the
study of personality has shifted toward narrower
research programs that examine specific aspects
of personality”
• In other words, most contemporary personality
research takes the nomothetic approach.
• Consistent with this modern trend, my second
year course “PSY230 – Introduction to
Personality” focuses exclusively on the modern,
nomothetic approach to personality psychology.
Warning
If you want to learn more about psychodynamic
theories (Freud, Adler, Jung), DO NOT take
PSY230
However, I hope to convince you in the rest of
today’s lecture that the nomothetic approach
examines interesting questions and provides
answers that are relevant to the understanding
of yourself and others.
The Scientific (Nomothetic) Study of
Personality and Individual Differences
Three Goals of Personality Psychology
1. Classification: How do people differ?
2. Causes: Why do individuals differ from
each other?
3. Consequences: What are the effects of
individual differences?
Examples
• How consistent are people in their behaviors?
When somebody is friendly to us, how likely is
it that this person is also friendly to others.
• Why are some people friendlier than others?
Nature vs. nurture – How much is personality
due to genetic differences? How much influence
do parents have on their children’s personality?
• What are the consequences of personality?
Does personality predict important lifeoutcomes such as longevity, happiness, and
income?
The Scientific Study of Individual Differences
• The nomothetic approach to personality
research relies heavily on correlations (textbook
pp. 54-56).
• Correlations provide information about the
relation between variability in two variables.
Examples
-Stability: Will individual differences in today’s
friendliness be the same in the future?
- Consistency: Are individual differences in
friendliness in one situation the same in a
different situation?
- Cause: Do genetic differences predict
individual differences in friendliness?
- Consequences: Do individual differences in
friendliness predict individual differences in
happiness?
SWLS Time 2 (End of Semester)
7
r = .73; r2 = 50%
6
5
4
3
2
1
1
2
3
4
5
SWLS Time 1 (Beginning of Semester)
6
7
Describing Individual Differences
• Everyday language provides thousands of
words to describe individuals (honest, caring,
ambitious, orderly, shy, modest, selfconfident,…)
• Correlations (and more advanced statistics)
show that individual differences in some of these
traits (characteristics) are related (e..g, shy is
negatively related to confident).
• As a result, it is possible to describe personality
with fewer dimensions.
The Big Five
• Initially, personality psychologists used
different traits to describe personality and
there exist hundreds of measures to measure
individual differences in these traits.
• In the past two decades, it was discovered
that these measures are related to each other
and can be reduced to five major traits that
differentiate one individual from another.
• The Big Five provide a comprehensive first
impression of an individual. They do not
capture all aspects of individual differences.
The Atlas Analogy
• I like to compare the Big Five to continents.
• Continents capture important differences
between regions of the word (Europe is different
from Asia).
• However, there still exists important differences
between countries in each continent (Germany is
different from Italy).
The Big Five
• Neuroticism – A disposition to experience
more negative feelings and low self-esteem.
• Extraversion – A disposition to be outgoing,
risk-taking, and cheerful.
• Openness – A disposition to be curious and
interested in novel and unconventional things.
• Agreeableness – A disposition to be caring and
modest
• Conscientiousness – A disposition to be
organized, ambitious, and dependable.
Measuring Personality Traits
• Self-report: The easiest and most widely used
method (e.g., “I am self-confident”). Assumes
that people are honest and know themselves.
• Informant reports: asking acquaintances (e.g.,
Joe is self-confident); more difficult to obtain;
assumes that others’ know the person well.
• Observing behavior: e.g., research assistants
rate personality based on videotapes of
behavior; time-consuming
•
•Experience sampling: ask participants to keep
a diary or momentary records of their thoughts,
feelings, and behaviors. Time-consuming,
requires high motivation and honesty of
participants.
• Each methods has its advantages and
drawbacks.
• The best way of measuring personality would
be to use multiple methods. For example, we are
currently conducting a study of married couples
in which we assess personality with self-reports,
informant reports, and experience sampling.
I tend to be relaxed and handle stress well.
I tend to worry a lot.
I tend to be quiet.
I tend to be outgoing and sociable.
I tend to be original and come up with ideas.
I tend to like to reflect and to play with ideas.
I tend to be considerate and kind to almost
everyone.
I tend to be rude to others.
I tend to do a thorough job.
I tend to do things efficiently.
1
2
3
Strongly disagree
4
5
6
7
strongly agree
Scoring of Your Personality Test
N
1+2
8.60
3.00
E
3+4
9.01
3.00
O
5+6
9.73
2.35
A
7+8
11.39
C
9+10
10.53
2.00
2.09
Stability of Personality
• Relative differences in personality are quite
stable over time.
• Stability increases over the life-span. It is not
fixed at 20.
• Personality changes with age:
- Neuroticism, Extraversion, Openness
decrease.
- Agreeableness, Conscientiousness increase.
Consequences of Personality
• Personality and Health
• Personality and Longevity
• Personality and Happiness
• Personality and Marital Satisfaction (Divorce)
• Personality and Job Performance (Income)
Personality and Health
• Stress is related to illness – Suppression of the
immune system.
• Neuroticism is related to stress-reactivity.
• We would expect neuroticism to be related to
health.
• However, neuroticism is more related to
subjective perception of symptoms
(hypochondria) than to objective health.
Personality and Longevity
• It is difficult to study the relation between
personality and longevity.
• The Terman-study assessed personality of
gifted children in the 1920s and 1930s. Now
researchers can examine which children are still
alive.
• Conscientiousness is the best predictor of
longevity.
• The processes underlying this relationship are
still unclear.
Personality and Happiness
• Extraversion is a disposition to experience more
positive affect (pleasant feelings).
• Neuroticism is a disposition to experience more
negative affect (unpleasant feelings).
• Extraversion and Neuroticism are the most
important personality predictors of lifesatisfaction.
Personality and Marital Satisfaction
• Research on personality and marital
satisfaction has a long history (since 1930s).
• Most studies show a negative effect of
neuroticism on marital satisfaction and a
positive effect on divorce.
• Another interesting finding is that people do
not marry on the basis of personality: Spouses’
personality scores are uncorrelated.
Personality and Job Performance
• It is plausible that some personality traits help
people in certain jobs:
- extraversion & service jobs
- optimism & sales jobs
• In addition, conscientiousness is a good
predictor of job performance in many different
jobs (work ethic)
• Conscientiousness becomes a stronger predictor
of job performance with higher autonomy.
Causes of Personality
• The relative contribution of genetic/biological
factors versus environmental/cultural factors
has been a major controversy.
• After the first child parents believe in
environmental factors.
• After the second child parents believe in
genetic factors.
• What is the evidence?
Twin Studies
• Before DNA testing (before the 1990s),
researchers had to rely on indirect evidence to
examine the influence of nature (genes) and
nurture (environment).
• Twin studies capitalized on the difference
between monozygotic twins (MZ) and dizygotic
twins (DZ).
• MZ twins are genetically identical.
• DZ twins share on average 50% of their genes,
just as much as other siblings.
Genetic Contribution to Personality
• To examine a genetic contribution, we can
compare the similarity of MZ twins to the
similarity of DZ twins.
• (Given certain assumptions), if MZ twins are
more similar to each other than DZ twins, then
genes must influence the trait.
• For example, the height of MZ twins correlates
very highly (r = .90), whereas the height of DZ
twins is correlated less highly (r = .45).
• Height is genetically determined.
• Numerous studies have demonstrated greater
similarity (higher correlations) for MZ twins than
for DZ twins for personality traits including the
Big Five.
• Today nobody doubts that genetic factors
contribute to personality.
• Twin studies also lead to the conclusion that
growing up in the same household has no
influence on personality.
• This finding is the topic of a heated debate as it
is hard to believe that parents have no influence
on the personality of their children.
Do Genes Determine Personality?
• Genes cannot directly influence experiences
and behavior.
• Genes influence biological processes, which in
turn influence experiences and behavior.
• Understanding these processes can help people
to change their personality.
• Neuroticism has been linked to a gene that
influences the reuptake of serotonin in the brain.
• Drugs like Prozac (SSRIs) change the biological
reuptake mechanism.
• Studies show that drugs like Prozac change
personality scores on a Neuroticism scale.
• SSRIs also have several side-effects. They are
used only when people suffer from abnormal
levels of depression and anxiety.
• What should we do when it becomes possible to
change personality at will?
Cultural influences on personality
• Cross-cultural studies show variation in
personality traits across cultures. For example,
HK Chinese score lower on Extraversion and
Openness.
• Acculturation studies show that personality
changes. HK Chinese who migrated to Canada
have higher extraversion and openness scores.
• In North America, Extraversion and
Neuroticism scores have increased over the past
decades.
Conclusion
• Personality psychology examines individual
differences.
• It relies more on correlations than on
experimental studies.
• It examines the major traits that differentiate
people.
• It examines the consequences of individual
differences for real-world outcomes.
• It examines the causes of individual differences.