Biological Approach to Personality

Biological Approach to Personality

Monday, November 17, 2014

2:30 PM

1. Hippocrates' Body Humors to Modern Neurochemistry: the search for the physical basis of personality has had a long history

1. Hippocrates' believed that four basic temperaments characterized human personality:

1. Melancholic or depressed (e.g. sad or dysphoric)
2. Sanguine or lively (very interactive with the world)
3. Phlegmatic or passive (mild-manner, not overly assertive, enjoys what life offers, happy to receive)
4. Choleric or irritable
5. The concentration of "humors" in the body brought about one or the other types

1. Modern neurochemistry agrees that hormones (humors) & neurotransmitters are the equivalent to Hippocrates' early speculations on the relationship between physical functioning & temperament
2. Freud agreed that the physical basis of personality existed in the form of biological instincts & drives. The pre-eminent drive for Freud was libido/sex drive, part of the survival instincts of every human
3. Kretchmer, a 19th century psychiatrist, had taken note of a relationship between physique & mental disorder & set out to discover the type of physique & its corresponding psychiatric diagnosis/mental illness

1. He identified that schizophrenia was related to lean physical type he called "asthenic"
2. On the other hand, manic-depressive tendencies were related to a stocky/"pyknic" body constitution
3. And finally the "athletic" type that could also show schizophrenic tendencies

1. Sheldon, a 20th century physician related 3 body types to personality (p. 229):

1. Endomorphic (pyknic)

• The endomorph is passive & sociable

1. Mesomorphic (athletic)

• The mesomorph is impulsive, assertive & sociable

1. Ectomorphic (asthenic)

• The ectomorph is shy, inhibited, & fearful

1. Glueck & Glueck (1950) found a relationship between Sheldon's body types & delinquency

1. Darin & the Theory of Evolution: the gradual change or evolution of advantageous characteristics is at the heart of Darwin's notion of natural selection

1. Organisms that possess adaptive characteristics are likely to survive & pass these on to their offspring
2. Those who possess these characteristic in environment which select for these features are more successful at the game of survival in that environment
3. Selection pressures are brought about by the environment as well as by members of one's own species

• Characteristics desired by female members of a species act as a selection pressure on the males. Those males that possess that feature (traits) are more likely to attract a female & have their genes passed along into the next generation

1. Evolution of physical characteristics:

1. The development of the nervous system

1. The central nervous system (CNS), consists of the brain, & spinal cord nerves
2. The peripheral nervous system (PNS), is comprised on nerves outside of the brain & spinal cord, & is also composed of the somatic nervous system: conveys info from the sense organs to the brain & from the brain to the muscles & glands
3. The autonomic nervous system is composed of 2 divisions that operate in opposition to one another:

• The sympathetic nervous system that's activated under "fight-or-flight" - an arousal system
• The parasympathetic nervous system that operates to restore calm & stability

1. The nervous system (NS) is composed of glial cells that provide support, structure & insulation to neurons which communicate info in & out of the NS

1. Neurons contain neurotransmitters that are released at the synapse. These transmitter are important for mood, energy & action
2. Neurotransmitters can either excite or inhibit receiving neurons, as can hormones which are chemical messengers that are released by glands & circulate through the blood system & excite/inhibit neurons

• For example, the pituitary gland located at the base of the brain works in conjunction with the hypothalamus to release hormones that stimulate the gonads (sex glands) to release androgens (testosterone), a male sex hormone, & estrogens, female sex hormones. Naturally, the sex hormones play a role in reproduction & sexual behaviour

1. Young Male Syndrome: human males are most aggressive with one another when they're competing for the attention of the opposite sex

1. A correlation exists between violent aggressiveness & age, such that most acts of homicide by males occur during the age period when competition for mates is most fierce -- early 20s
2. Aggression Is also related to hormone output which is high during the teens & early 20s

• Testosterone in males has been linked to aggressive behaviour

1. Aggression: although aggression is universal & occurs among both males & females, males engage in more direct aggression: physical & females equally aggressive, but engage in more indirect expressions: verbal taunts, ridicule, gossip

1. Testosterone has been linked to aggression in males. Levels are highest from mid-teens to early-20s when aggression among males in high
2. There seems to be a positive correlation between testosterone levels & a variety of aggressive & anti-social behaviours (Dabbs et al., 1987)

1. On the other hand, serotonin may inhibit aggression & people who are aggressive have low serotonin levels
2. Spoont (1992) hypothesized that in countries where tryptophan is lowest in the diet, the homocide rate is high. Tryptophan is a precursor of serotonin. Thus, reduced activity of serotonin may cause a disinhibition effect leading to destructive & aggressive impulses
3. Brain region such as the amygdala is the limbic (emotion) system when stimulated produce rage & aggression. Diseases which attack the temporal loves (e.g. rabies) where the amygdala is located may lead to violent outbursts (Lentz et al., 1982)

1. Suppression of the temporal love through drugs/surgery suppresses violent behaviour

1. Biology & Personality: earliest observable differences in personality are related to inherited temperament styles

• Temperaments appear early in life & remain relatively consistent across the life span
• Temperament is the raw material out of which personality evolves

1. Sociability: style of relating to the social environment

1. Infants may be described as:

• Difficult - actively withdraw rather than approach people
• Easy - actively approach people
• Slow to warm up  initially feared & gradually overcome this & approach people (Bowlby & Ainsworth attachment styles: secure, ambivalent, avoidant & disorganized)

1. Consistency of sociability styles is noted in longitudinal studies starting in infancy & proceeding through childhood, adolescence & adulthood

• Shy boys delay marriage, whereas shy girls were more likely to follow a conventional pattern of marriage, childbearing & homemaking (Caspi et al., 1988)

1. Monozygotic twins (twin study method) are more alike in sociability than dizygotic & ordinary siblings

• Correlations for monozygotic twins are +0.54 & for dizygotic twins +0.21

1. Adopted children (adoptee method) are more like biological parent than foster parents
2. Sociability overlaps with extraversion since extraverts are more likely to engage in approach behaviours toward others

• Eysenck says that extraversion is largely inherited. For example, extraversion & neuroticism are more closely related in monozygotic than in dizygotic twins

• Correlations for monozygotic males & monozygotic female is about +0.50 for both extraversion & neuroticism. Whereas for dizygotic twins the correlation drop to about +0.18 to +0.20 for extraversion & neuroticism
• Swedish adoption study & twin study of aging reveals the heritability of extraversion to be about 0.41. heritability estimates may be as high as +0.72

1. Eysenck maintains that the differences in extraverts, from introvert, is due to differences in a particular brain system known as the ascending reticular activating system (ARAS) (p. 251)

• When the ARAS is functioning at a high level, the person report feeling sharp, alert & attentive
• When the ARAS is operating at a low level, the person reports feeling dull, drowsy & sluggish
• Extraverts have a low level of ARAS functioning, are less cortically aroused, & have a higher threshold of sensitivity. Thus, they attempt to compensate for this low arousal by seeking environments that are stimulating & exciting. They tend to be stimulus hungry & are sensation seeking
• Zuckerman finds that sensation seeking involves seeking varied, novel, complex & intense sensations & experiences (p. 256)

• Both impulsivity & sensation seeking are more closely related to Eysenck's Psychoticism (P) dimension than to Extraversion (E)

• It's highly heritable with an heritability estimate of 0.60
• Persons with P dimensions are risk-taker & more inclined to experiment with drugs, sex & sport for the sake of excitement
• They show pronounced orienting response
• Impulsivity & sociability are part of the sensation seeking pattern
• The mechanism underlying sensation seeking is biochemical involving the monoamine class of neurotransmitters & sex hormones

• Dopamine drives approach behaviour & serotonin inhibits approach

• Sensation seeking peaks in males during late teens to the early 20s

It seems to correlate with high testosterone levels at precisely those times when this sex hormone is high during the teens & early 20s. It may be that testosterone affects the dopamine system by influencing an enzyme that regulates dopamine action (B MAO)

Zuckerman agrees with Freud that ultimately the biological bases of personality will be known & will illuminate the forces responsible for human motivation

1. Additional Temperaments - Biology & Personality

1. Emotionality: tendency to be physiologically aroused. Emotionality parallels the negative pole of personality known as Neuroticism

1. Ease of arousal & intensity of arousal can be gauged
2. Ease of arousal deals with degree of stimulation require to elicit arousal, & intensity deals with vigor of response
3. Studies reveal that emotionality has an inborn component & is in evidence by 2 to months of age. High & low emotionality is consist throughout infancy, childhood,