Biological Bases of Personality Flashcards
Neurotransmitters Brain structures Hormones
Early ideas: The Four “Humours” and Personality
Sanguine
Melancholic
Choleric
Phlegmatic
Ancient Greek thinkers: Hippocrates and Galen
- Personality patterns or temperament is dependant on various fluids in one’s body
four main humors
- Blood: very cheerful = sanguine
- Black bile: depressive = melancholic
- Yellow bile: angry = choleric
- Phlegm: calm = phlegmatic
no empirical evidence
Idea remained influential
e.g. Ivan Pavlov (famous Russian psychologist)
- Weak: anxious = melancholic
- strong unbalanced = irritable / choleric
- strong balanced slow = calm / phlegmatic
- strong balanced mobile = lively / sanguine
Neurotransmitters and Cloninger’s theory
Dopamine & Novelty Seeking
Serotonin & Harm Avoidance
Norepinephrine & Reward Dependence
Empirical tests of Cloninger’s theory
Neurotransmitters and Cloninger’s theory
Firing of neurons: basis of emotions, thoughts, behaviours
Neurotransmitters are biochemical substances involved in the communication among neurons
Level of neurotransmitters might influence one’s personality
Focus is on three neurotransmitters active in the brain and spinal chord (the central nervous system)
How neurotransmitters work?
End of axon stops adjacent to the dendrite
Gap is called synapse
This is the location of communication between nerve cells
Axon terminal releases chemicals that affect the dendrites on other side of synapse
Dopamine and Novelty Seeking
Transmission of signals of reward, in response to things that feel pleasurable and exciting
Cloninger: personality characteristics related to one’s response to PLEASURE and EXCITEMENT
Underactivated dopamine system…
Parkinson’s disease: Extremely inactive
- Lack of interest in new or fun activities
- Uncoordinated movements
Overactivated dopamine system
Cocaine: increases dopamine activity
- Extremely aroused
- Increase in novelty seeking behaviour
Serotonin and Harm Avoidance
Inhibits the transmission of signals of punishment,
Preventing neurons to send message in response to things that feel harmful or unpleasant
Cloninger: personality characteristics related to pain and anxiety
Low levels of serotonin = high in “Harm Avoidance”
- Worry/pessimism
- Fear of uncertainty
- Shyness with strangers
- Fatigability
Antidepressant drugs such as
Prozac
Paxil
-> keep the serotonin system active
Inhibition of transmitting punishment signals
Reduction of negative emotions such as anxiety and depression
Norepinephrine and Reward Dependence
Inhibits the transmission of signals of responding to stimuli that in the past have been associated with reward
Signals of conditioned reward
Cloninger: personality characteristics related to people and things that have been associated with pleasure
Low levels of norepinephrine = high in “Reward Dependence”
- Sentimentality
- Warm communication
- Dependence
Very inactive norepinephrine system
The tendency to develop strong sentimental attachment
Empirical test of Cloninger’s theory
Identify people who have different alleles of a gene that affects neurotransmitters
Compare people who have a different allele to see if there are any differences in the assumed personality traits
Comings et al. (2000): Investigation of the role of 59 genes in personality traits including:
7 related to dopamine
12 related to serotonin
9 related to norepinephrine
Each set of genes tended to be related to more than one of Cloninger’s personality dimensions
- Reward Dependence was more strongly related to norepinephrine genes than to the other genes
- Less clear support for the unique relations between Harm avoidance and serotonin genes and between Novelty seeking and Dopamine genes
Brain Structures
Gray’s theory
Eysenck’s theory
Gray’s Theory: Reinforcement Sensitivity Theory (RST)
Brain regions work together as systems that underlie personality
- The Behavioural Activation System (BAS)
- The Behavioural Inhibition System (BIS)
- The Fight-or-Flight System (FFS)
The Behavioural Activation System (BAS)
Brain regions responsible for receiving signals from the nervous system which indicates that REWARDS are being experienced
Go-system
Go-system
Encourage pursuit of rewards
Communicating the pleasurable and exciting nature of rewards
People differ in the sensitivity of their BAS system
Stronger or more sensitive system = stronger pursuit of reward
Impulsivity, seeking pleasure and excitement
Cloninger’s Novelty Seeking dimension
The Behavioural Inhibition System (BIS)
Brain regions responsible for receiving signals from the nervous system which indicate that PUNISHMENTS are being experienced
Stop-system
Stop-system
Encourage avoidance of punishments, communicating the painful and frightening nature of punishments
People differ in the sensitivity of their BIS system:
Stronger or more sensitive system = stronger avoidance of punishments
Anxious, avoid pain and danger
Cloninger’s Harm Avoidance dimension
The Fight-or-Flight System (FFS)
In response to extremely threatening situations
People differ in the sensitivity of their Fight-Flight system:
Stronger or more sensitive system = more ready to fight or to flee in case of emergency
Showing extreme reactions: aggressive response, leaving hurriedly
Some researchers suggest that there might be a negative link with Cloninger’s Reward Dependence dimension
but there is not yet empirical evidence showing such association
Eysenck’s Theory
Strict standards for scientific pursuits
- Conceptual clarity
- Precise measurement
- Factor analysis
Early theory: two superfactors
EN Theory of personality
Extraversion - Introversion
Neuroticism – Stability
Later theory: three superfactors
PEN Theory of personality
Extraversion - Introversion
Neuroticism – Emotional Stability
Psychoticism
Extraversion
People differ in the strength of their reactions to stimulations of their senses - arousability of their brains
Preference for high versus low level stimulation
Extraverted people
- Seek stimulation and sensation
- Sociable
- Lively
- Active
- Assertive
- Enjoy loud music
- Meetings
- Parties
Introverted people
- Avoid stimulation
- Prefer quieter surroundings
- Avoid large crowds
Individual differences in Extraversion are governed by the…
Ascending reticular activating system (ARAS)
ARAS is located in the brain stem, where the spinal cord meets the brain
Nervous system receives stimulation from the environment
ARAS regulates the amount of stimulation that is admitted to the brain from the nervous system
If one’s ARAS allows little stimulation, one feels UNDERAROUSED and thus SEEKS STIMULATION
Extraverted personality
If one’s ARAS allows admits a lot of stimulation, one feels OVERAROUSED and thus AVOIDS stimulation
Introverted personality
Neuroticism
People differ in the strength of their reactions to stressful stimuli
Very sensitive vs. much less sensitive to stress
Very neurotic people
Feel a great deal of worry and nervousness, anxioux
Emotionally stable people
Feel little stress
Individual differences in Neuroticism are governed by the
Limbic system
The limbic system consists of several connected structures
Regulate stress responses
Manage stressful stimuli, more emotionally stable
Overwhelmed by stressful stimuli, tend to be more neurotic
Psychoticism
High levels in psychoticism -> higher levels of testosterone and low levels of the enzyme mono-amine oxidase (MAO)*
MAO
Involved in the inactivation of neurotransmitters such as serotonin, dopamine
Very psychotic people
Aggressive, cold, egocentric, impersonal, impulsive, tough-minded, antisocial
High levels of psychoticism
Associated with criminal behaviour, mental illnesses, but also with creativity
Gray’s and Eysenck’s dimensions: Empirical evidence
Lemon juice test (Eysenck & Eysenck, 1967)
The stimulation produced by the lemon juice is perceived more strongly by introverts than by extraverts
Introverts produced more saliva than extraverts
Geen (1984): Effects on arousal and performance
Participants: introverts and extroverts had to complete a learning task while being exposed to noises
Measures: levels of arousal indicated by heart rates and levels of skin conductance
Geen (1984): Findings
Choice condition: extraverts and introverts show comparable arousal levels (similar heart rates and skin conductance) because they have chosen their optimal/preferred levels of noise
Assigned-same condition condition (matches their personality): Introverts in the quiet condition and extraverts in the loud condition show similar results as participants in the choice condition
Assigned-different condition:
Introverts in the loud condition -> show higher arousal levels (overstimulated)
Extraverts in the quiet condition -> show lower levels of arousal (understimulated).
Conclusion: Geen (1984)
Introverts prefer lower levels of stimulation than extraverts
Introverts are more aroused/react more strongly than extraverts under equal levels of stimulation
Introverts performed better than extraverts under quiet noise condition
Extraverts performed better than introverts under loud noise condition
Results of these laboratory experiments are broadly consistent with Eysenck’s theory of the biological bases of Extraversion
More research is needed to understand the brain structures that underlie personality
Some studies produced more complex patterns of results that are only partly consistent with Eysenck’s theory
Zuckerman and his colleagues found evidence for three personality factors consistent with Eysenck’s dimensions but also obtained evidence for five factors (not Big Five)
Unlike Eysenck’s ideas, Zuckerman suggested that each personality dimension is influenced by
complex interactions between several brain structures, neurotransmitters, and hormones,
rather than by a single brain structure, neurotransmitter, or hormone
Hormones
Testosterone
Cortisol
Oxytocin
Hormones
Biological chemicals produced in glands of body parts then transmitted to other body parts
Affect neuron activity and may therefore influence personality
Testosterone
Responsible for many physical characteristics of men
Development of male reproductive organs
Development of secondary sex characteristics
Levels are at least 10 times higher in men than in women
Testosterone levels vary between individuals but also influenced by events and situations
Experiences of winning and losing, e.g. basketball fans
Experiences of winning and losing (Bernhardt, Dabbs, Fielden, & Lutter, 1998) e.g. World Cup Soccer
Brazil won on penalties after extra time
Italian fans dropped out of participation more than Brazilian fans
Levels of testosterone during early periods of development may influence behaviour later in life
Girls exposed prenatally (in womb) to high testosterone levels tended to prefer toys that are usually more preferred by boys than by girls
How do testosterone levels relate to behaviour and personality?
Studies of Dabbs and colleagues: sample of 240 members of fraternities
Fraternities with higher average levels: rude, wilder, unruly, rambunctious
Fraternities with lower average levels: kind, more socially responsible, better academic achievement, more friendly
Studies of Dabbs and colleagues: Sample of 692 prison inmates
Higher testosterone levels:
- Crimes of a violent/sexual nature
- Less with drug offences, theft, or burglary
- More rule breaking in prisons
Men versus women
Great difference in testosterone levels
Much smaller differences and considerable overlap in distribution of personality traits
-> Testosterone is clearly not the only factor influencing personality
Cortisol
Hormone released by the adrenal cortex
Which triggered by stress to prepare the body for action
Increase in blood pressure and blood sugar
Suppression of the immune system
Loney et al. (2006): Emotional reactivity - levels of “callous-unemotional” traits
Among boys but not among girls -> higher levels of callous-unemotional traits were associated with low cortisol levels
Little cortisol = more emotionally insensitive
Rosenblitt et al. (2001): Sample of 143 college students
Investigated the associations between Testosterone, Cortisol and sensation seeking scores
No significant associations among women
No significant associations for testosterone in sensation seeking
High sensation seeking men had significantly lower cortisol levels
Oxytocin (the love hormone)
Hormone produced in the hypothalamus
Released by the pituitary gland
In women and female mammals, oxytocin is released when giving birth, breastfeeding, experiencing orgasm
Also men have oxytocin, facilitating a man’s emotional attachments with his partner and children
Zak, Kurzban, and Matzner (2005): Students playing a trust game involving money
Students with higher (versus lower) levels of oxytocin trusted other students more in how to divide some money
More trustworthy students (dividing the money equally) had higher levels of oxytocin
-> Oxytocin plays a role in cooperative relationships and interpersonal attachment
