Biological Aspects of
Personality
Theories of Personality
Prepared by: Jim Messina, Ph.D.
Key Biological Theorists
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Charles Darwin
Ivan Pavlov
Hans Eysenck 1916-1997
Francis Galton
Evolutionary Personality
Theory
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Application of Darwin’s Theory of
Evolution
Function of a survival characteristic
evolves over time
Belief that many of individual
characteristics are “in our bones” in
our genes
Natural Selection
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Process by which certain adaptive
characteristics emerge over
generations
Examples of Genetic
Personality Types
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Angelman Syndrome – chromosome 15
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Friendly
Oral driven
Downs Syndrome - chromosome 21
 Friendly – easy to get along with
 Caring, Loving
 Approval seeking
Study of Temperaments-Based
on Work of Pavlov
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Temperament: stable individual
differences in emotional reactivity which
remain stable as children mature
Different nervous system responses to
unpleasant stimuli
4 Basic Aspects of
Temperament
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Social-Introversion-Extroversion- seek or
avoid being with/in front people
Emotionality-fearful, angry, mood
swings vs relaxed, calm, placid, stable
Activity-vigorous, always in motion vs
passive, lethargic
Impulsive-aggressive-bully vs peace
maker, plans vs quick changes, cold vs
conscientious & friendly
Introversion vs Extroversion
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Hans Eysenck – ties this to central
nervous system – Biologically based
personality theory
Extroverts – Low level of Brain arousal
and seek stimulation
Introverts – High level of Brain arousal
shy away from over-stimulation
Nervous System Arousal
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Stable people-well-modulated nervous
systems
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Neurotic people-very reactive nervous
systems
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Tests: EEG, Electrodermal measure (lie
detector)
Sensation Seeking
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Seek new challenge or new high
Seek highly stimulating activities
Attracted to unknown
Low level of natural (internal biological)
activation –seek arousal from
environment
Left and right side of Brain
The Brain
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Brain reaches its maximum number of
synaptic connections and its greatest
metabolic activity around age 3 or 4
Brain Hemispheric Hypothesis
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Left side of Brain-Role in Positive
Emotions-Creative side of Brain
Right side of Brain-Role in Negative
Emotions-Methodological, systematic
side of Brain
Try out this test to get the impact of
right and left hemisphere operations
Top view of Brain
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genu of the corpus collosum
head of caudate nucleus
putamen
globus pallidus
thalamus
tail of caudate nucleus
splenium of corpus callosum
amygdala
substantia nigra
PET Scan of Brain of Adult
with ADHD
PET Scans
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Demonstrates metabolism of
glucose in brain under arousal
Brain on left is normal adult brain
under arousal
Brain on right is Brain of Adult with
ADHD –
frontal lobe of brain most involved
in adults with ADHD
Messages from Brain Travel by
Nervous System
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The Central Nervous
System is the
Communications
Highway of the body
Brings help to the
body based on the
messages it screens
from the
environment
Neurons where the messages
are delivered!
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Bio-chemical
electrical impulses
create a cascade of
effects based on the
message sent to
various organ
receptors of the
body
Neurotransmitters
Impacted Too!
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Not only are there
physiological
changes but there is
altering of
neurotransmitters
based on messages
from brain
Absence or
overabundance can
create whole new set
of consequences
Neurotransmitters
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Brain = Billions of Brain Cells-Neurons
Neurons transmit information –
electrical conduction within nerve cells
& between nerve cells
Message once carried through body cell
(Axon) crosses space –Synapse to
receiving cell
Neurotransmitters
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Tip of Axon-tiny sacs contain neurotransmitter
chemicals which are automatically released by
sending nerve cell
Neurotransmitter chemicals excite receiving cell
causing cell to fire to send message through its
own body-Axon to next receiving cell
Once message received neurotransmitter is
deactivated and taken up from synapse and stored
in sacs so as not to cause repeated firing of the
receiving cell
Types of Neurotransmitters
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Dopamine-dopaminergic system
Norepinephrine-noradrenergic system
Serotonin-serotonergic system
Control senses, thinking, perception,
mood, attention, and behavior
Unfortunately at this time we can not
measure amount for baseline therapeutic
levels
Hans Eysenck
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3 Type Theory –Biological DeterminismHeredity in Everything
E – Extraversion – linked to ascending
reticular activating system (ARAS)-reticular
formation of Brain Stem
N – Neuroticism – linked to limbic systembrains emotional center regulates sex, fear &
aggression
P – Psychoticism – linked to endocrine glandespecially which controls sex drive
Eysenck’s Types
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E-extraversion – introversion
Neuroticism-stability
Psychoticism-superego functioning
People show degrees of all 3 types
Encouraged Twin studies especially of
identical twins who were adopted
separately
Sir Francis Galton
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Supposition that Upper Class
Englishmen were a superior population
Began the study of adoptive twins
Began the “eugenics” movement
Encouraged eminent families to have
lots of children to improve the human
blood lines
Eugenics
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Good Birth or Good Genes is the cause
of peoples’ high intelligence and stable
emotional well-being
Recommend forced sterilization of the
poor
Kin Selection
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Nieces and nephews of people with
certain traits thought to be genetic
based- homosexuality,
schizophrenia, bipolar disorder –
genetic tendency toward these
conditions survives since nephews
and nieces share some genetic
makeup with uncle or aunt who has
these traits.
Mediated effects of Biology
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Disease-Parkinson’s, ear, heart, lung,
systemic, surgery
Poisoning-mercury, lead, manganese
Brain disease-Alzheimer’s, strokes,
epilepsy, tumors
Illegal drugs, LSD, cocaine, crack
Somatotypology-W.H.Sheldon,
1942
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Three Body Types have influence on
personality:
Mesomorphs-muscular, large boned,
athletic
Ectomorphs- slender, bookworm
Endomorphs- overweight, roly-poly,
good natured
Survival of the Fittest
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Darwin’s concept that the fittest survive
over time
Misused to mean: weak creatures
should not survive
Pseudoscientific justification for the
oppression of minorities
Social Darwinism
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Applying evolutionary theory in a crude
way to society
Not only individuals but societies and
cultures naturally compete in survival of
the fittest
It was ok to subjugate those seen as
inferior race or culture
Sociobiology
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Scientific study of the influence of
evolutionary biology on individual
responses regarding social matters
Focus: Analysis of human aggression,
human courtship and raising young
children
Attachment
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Close bond – develops shortly after birth
between infant and caretaker(mother)
Infant clings, gurgles, smiles to attract
caregiver-so that caregiver will nurture
the infant
Attachment system insures survival of the
of infant-ensures passing of mothers
genes
Evolutionary function for cuteness of
infants
Human Genome Project
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The accomplished task of identifying
the tens of thousands of genes in
chromosomes
Develop treatments for inherited
diseases
Movement towards Gene Therapy
Potential threat: genetic engineering
Biological Determination
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Personality simply a matter of genes,
brains, and hormones
Behavior is determined by biological
tendencies
Minimizes the human potential for
growth and change