Personality is derived from the Latin word, persona,
where it originally referred to a theatrical mask. The study of personality
started with Hippocrates' four humors and gave rise to four temperaments.
Personality is the dynamic organization within the individual of those
psychophysical systems that determine his characteristics behavior and thought.
Weinberg and Gould defined personality as the
characteristics or blend of characteristics that make a person unique. The
American Psychological Association defines personality as individual
differences in characteristic patterns of thinking, feeling, and behaving.
The study of personality focuses on two broad areas:
·
understanding individual differences in
particular personality characteristics, such as sociability or irritability and
· understanding how the various parts of a person come together as a whole.
Biological Basis of Personality
The biological perspective on personality emphasizes the
internal physiological and genetic factors that influence personality. It
focuses on why or how personality traits manifest through biology and investigates
the links between personality, DNA, and processes in the brain. It is primarily
accomplished through correlating personality traits with scientific data from
experimental methods such as brain imaging and molecular genetics. The
biological basis of personality is the theory which states that the anatomical
structures located in the brain contribute to personality traits. This is
derived from neuropsychology, a branch of science which studies how structure
of the brain is related to various psychological processes and behaviors. For
instance, in human beings, the frontal lobes are responsible for foresight and
anticipation, and the occipital lobes are responsible for processing visual
information. In addition, certain physiological functions such as hormone
secretion also affect personality. For example, the hormone testosterone is
important for sociability, affectivity, aggressiveness, and sexuality.
Other studies also show that the expression of a
personality trait depends on the volume of the brain cortex it is associated
with. Personality neuroscience involves the use of neuroscience methods to
study individual differences in behavior, motivation, emotion, and cognition.
Personality psychology has contributed much to identifying the important
dimensions of personality, but relatively little to understanding the
biological sources of those dimensions. However, the rapidly expanding field of
personality neuroscience is increasingly shedding light on this topic. DeYoung
provided a survey of progress in the use of neuroscience to study personality
traits, based on the Big Five dimensions:
·
extraversion,
·
neuroticism,
·
agreeableness,
·
conscientiousness,
·
and openness or intellect.
The biological approach to
personality has also identified areas and pathways within the brain that are
associated with the development of personality. A number of theorists, such as
Hans Eysenck, Gordon Allport, and Raymond Cattell, believe that personality
traits can be traced back to brain structures and neural mechanisms, such as
dopamine and serotonin pathways. One of the best known biological theorists was
Hans Eysenck, who linked aspects of personality to biological processes.
Eysenck argued that introverts had high cortical arousal, leading them to avoid
stimulation. On the other hand, he believed that extroverts had low cortical arousal,
causing them to seek out stimulating experiences.
The emphasis is placed on the
biochemistry of the behavioral systems of reward, motivation, and punishment.
This has led to a few biologically based personality theories such as Eysenck's
three factor model of personality, Grey's reinforcement sensitivity theory, and
Cloninger's model of personality. The Big Five model of personality is not
biologically based, but still some studies provided biological support for this
model. The most influential scientists in the field of biology-based
personality theories are Hans Eysenck and Jeffrey Alan Gray. Eysenck used both
behavioral and psychophysiological methodologies to test and develop his
theories.
So, the Biological theories of personality are a group of theories that argue for the nature (or biological) side of this ongoing debate where one side argues that we are born a specific way (nature), while the other side argues that we are influenced to become who we are (nurture).
History of Biology-based
Personality Research
It has been, since the ancient
Greek time, attempted to explain personality through spiritual beliefs,
philosophy, and psychology.
Some of the earliest and most
famous examples of the biological perspective is ideas brought forth by Charles
Darwin. Darwin was the father of evolutionary psychology. His theories of
evolution suggested that species evolve over time; members of said species with
stronger traits were more likely to reproduce and pass those traits onto their
offspring. Evolution doesn’t just favor physical traits, like taller people or
faster swimmers.
Historically, studies of personality have traditionally come from the social sciences and humanities, but in the past two decades neuroscience has begun to be more influential in the understanding of human personality. Eysenck published a book called “Dimensions of Personality,” describing the personality dimensions of extraversion and neuroticism. He has many publications in this field. Gray, his student, studied personality traits as individual differences in sensitivity to rewarding and punishing stimuli. The significance of Gray's work and theories was the use of biology to define behavior, which stimulated a lot of subsequent research. The biology-based personality research is a relatively new topic and recently, in 2004, there was a conference entitled “The Biological Basis of Personality and Individual Differences”. This resulted in the publication of a book “The Biological Basis of Personality and Individual Differences”.
Genes and the Brain
Where do biologists find our
traits? In our genes and our brains. To test this theory, psychologists have
studied identical twins. Identical twins have the same genes, but those who are
separated at birth will grow up in completely different environments. When
scientists look at their similarities and differences, they can get a sense of
what is nature and what is nurture.
Using Identical Twin studies,
we can narrow down what percentage of traits may be due to genetics. If a trait
can be passed down through a gene, we call it "Heritable".
A variance between multiple
people that can be accounted for by genetic differences.
Some of our personality traits
are influenced by genes, and some are not.
For example, according to
identical twin personality research, these traits have been correlated to be
influenced by genetics:
·
Social Closeness: 15%
·
Achievement Orientation: 38%
·
Traditionalism: 59%
·
Imagination: 74%
One example of a gene that can
influence a trait is the Dopamine-4 Receptor Gene. This gene has been connected
with the trait of thrill-seeking and people enjoying novelty.
Biological Perspective of Personality
Disorders
Studying personality isn’t just
about whether someone is naturally funny or open to new experiences. Answers
must also be gathered regarding personality disorders. But there have been studies
to prove that the structure of the brain may influence the development of a
personality disorder. For example, smaller regions of certain parts of the
brain may be linked to Cluster B personality disorders. Abnormalities in the
brain have been linked to Schizotypal Personality Disorder. This is not to say
that environmental factors play no role in personality disorders, but that
these findings should continue to be explored.
Sources and Additional
Information:
https://practicalpie.com/biological-theory-of-personality/
https://opentext.wsu.edu/psych105/chapter/10-7-biological-approaches-to-personality/