Biological Basis of Personality:Genetics and twins studies
123 pairs of identical twins and 127 pairs of fraternal twins
Measured on “Big Five” personality dimensions
Results suggest that personality differences in the population are 40 - 60% heritable.
The personality of adopted siblings No more alike than randomly selected persons Largely unrelated to adoptive parents
Doesn’t parenting style affect adult personality? Peers, not adults, exert the most influence on
personality (Rowe, 1994; Harris, 1998) But a minimum amount of parenting is critical for the
avoidance of antisocial behavior (Lykken, 2000)
Biological Basis:Genetics and adoption studies
Biological Basis: Specific genes for specific traits?
A gene that regulates a particular dopamine receptor is associated with novelty seeking One form of this gene produces deficiency in dopamine and
people seek out novel experiences to increase the release of dopamine, which is related to feelings of reward and pleasure
A gene that regulates serotonin is associated with neuroticism and agreeableness
However, typically, a personality trait will be a product of many genes and the presence of an environment appropriate for gene expression
Biological Basis: Temperaments in Infancy
Temperament A general tendency to feel or act in a certain way that is strongly linked
to biology If infants show such tendencies, these tendencies must be “hard-wired”
(i.e., must be biological) since the environment has not yet had a chance to exert its influence
Shyness (Kagan & Snidman, 1991) 15-20% of newborns (as young as 6 weeks) respond to new situations or
strange objects by becoming distressed (i.e., crying, etc.) At 4 years old, these children are described as shy by their parents Likely to be shy as a teenager More likely to be depressed as a young adult
The Neurophysiological Mechanisms of Extraversion
Extraversion Less than optimal levels of activity in the ascending reticular
activating system (part of the brain stem) Chronic underarousal leads extraverts to seek stimulation Extraverts work and perform better in noisy environments
The behavioral approach system (BAS) is stronger in extraverts
The BAS leads organisms to approach stimuli in search of rewards Extraverts have heightened dopamine activity in the reward center of
the brain (i.e., the nucleus accumbens, a part of the limbic system) Extraverts report high levels of energy, desire, and self-confidence
The Neurophysiological Mechanisms of Introversion
Introversion Greater than optimal levels of activity in the ascending
reticular activating system (part of the brain stem) Chronic overarousal leads introverts to avoid stimulation Introverts are more sensitive to stimulation, including pain
The behavioral inhibition system (BIS) is stronger in introverts
The BIS is sensitive to punishment and leads organisms to inhibit behavior that might lead to danger or pain
Introverts have heightened activity in the frontal lobes (which are known to inhibit socially inappropriate behavior) and in the amygdala (which processes stimuli related to punishment and fear)
Introverts are anxious about social situations because they fear negative outcomes
Personality Is Evolutionarily Adaptive
Natural selection has shaped the human genome over the course of evolution.
Adaptive personality traits were passed along to increasing numbers of individuals in future generations.
For example, It is easy to imagine how being competitive might lead a person to obtain great rewards and how being competitive would be passed on.
But if traits are adaptive, why are there such great individual differences among people?
Natural selection ought to make people more similar rather than more different. Individual differences may be the result of evolution having endowed us
with multiple strategies for survival The strategy an organism selects depends on the particular environment
For example, a competitive person in a cooperative society (or a cooperative person in a competitive society) would have a distinct advantage
Such diversity within a group may confer a selective advantage over groups that have less diversity
For example, it may be good for a group to have both competitive and cooperative members Competitive individuals often risk their physical well-being and hence do not survive, while
cooperative members do
Personality Consistency over Time
In general, personality is consistent over the lifespan
Where you rank relative to others on personality traits changes relatively little over time.
This supports the notion that traits are hard-wired
However, is personality more consistent at some points in the lifespan?
Evidence indicates that personality is least stable during childhood
Consistency increases with age
Personality Change over Time
Your rank order relative to others on the trait of conscientious changes relatively little over time
If you’re very conscientious relative to others when you’re 20 years old, the same will likely be true when you’re 50 years old
However, conscientiousness in everyone tends to increase over time
This is true in multiple cultures
Levels of personality (McAdam):Some change, some don’t
Dispositional traits (or basic tendencies) The Big Five Not likely to change in a particular individual over time
Personal concerns These, and the strategies we use to meet them, change according to
situation or developmental stage However, even though the particular concerns and strategies change,
the way they change corresponds to a person’s basic tendencies Thus, these changes are often called characteristic adaptations
Life stories These evolve over time to provide a person’s life with a sense of unity
and meaning For example, someone might see themselves as having a “rags to riches” life
story
Personality change: Brain injury and psychological medications
Phineas Gage Alzheimer’s disease
There is some evidence that personality changes are the first signs of early stage Alzheimer’s (Moran et al., 2004)
Prozac Antidepressant that works by increasing the activity of
serotonin When taken by individuals without depression, it can cause
personality changes, such as Increased social dominance and extraversion Decreased hostility and neuroticism
The self: Self-awareness
Self-concept Who you think you are. Influences your daily choices.
Self as “I” (knower) vs. self as “me” (known) The knower is you thinking, feeling, making decisions, etc. The known (the objectified self) is the knowledge you hold about your self; your
self-concept Self-awareness theory
The “I” thinking about the “me” We spend only about 8% of our time thinking about ourselves.
Objective self-awareness pushes us to act in accordance with our self-concept Self-discrepancy is the awareness that we are not acting in accord with our self-
concept This realization can generate negative emotions within ourselves See next slide
Self-Awareness Theory
Self-Conscious Persons
Self-focusing situations
Self-Awareness
Change Behavior to Match Standards
Self-Discrepancies
Escape from Self-Awareness
Escape from self-awareness is sometimesaccomplished through the consumption of alcohol. Thiscan also provide an excuse for future failures.
The self: Self-schema
Self-schema The cognitive component of our self-concept The working self-concept
The immediate (present moment) conception of our self This can change from situation to situation
That is, the working self concept is formed “on-line” Independent vs. interdependent self-construals
People that live in individualistic cultures tend to have independent self-construals
In an individualistic (typically Western or industrialized) culture, personal goals and preferences take priority over group allegiances.
People that live in collectivist cultures tend to have interdependent self-construals
In a collectivist (typically Eastern or agrarian) culture, cooperation and group harmony take priority over purely personal goals.
See the next two slides
The self: Self-esteem
Self-esteem The evaluative or emotional component of the self-concept
Am I worthwhile or worthless? Good or bad? Reflected appraisal
In large part, people view themselves as others view them. Sociometer theory
When a person behaves in ways that lead to rejection by their social group, their self-esteem will be reduced.
Terror management theory Exaggerations of personal importance reflect attempts to buffer anxiety about
inevitable death. Self-esteem is only weakly related to objective life outcomes.
Although people with high self-esteem do report more happiness. There are some downsides to having high self-esteem.
When some people with high self-esteem are challenged, they can become bullying, violent, or boastful.
The Self-Esteem Cycle
High Self-Esteem
Self-Credit
Success High Effort
Positive Expectations
Low self-esteem and negative self-evaluations are related to pessimistic explanatory styles, which in turn are related to negative consequences for the immune system.
The self: Positive illusions
People think of themselves in overly favorable terms The better-than-average effect.
Most people describe themselves as above average in almost every way. Self evaluative maintenance
Self-esteem is influenced by An individual’s performance How relevant that performance is to that individual’s self-concept How that performance compares to the performance of people that are
significant to that individual Social comparison
People with low self-esteem tend to make upward comparisons with others that are superior to them.
Self-serving bias People with high self-esteem take credit for success, blame failures on
outside factors, and attribute criticism to envy or prejudice.