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Chapter 7

PSYB30H3 Chapter 7: Chapter 7

Course Code
Lisa Fiksenbaum

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Physiological Approaches to Personality
Studies have shown that traumatic brain injury can lead to large changes in
One of the most common changes in personality following brain injury
is a diminished ability to inhibit or control one’s impulses
This has been found in children who experienced brain trauma,
adults with traumatic brain injuries + elderly persons whose
brain has been injured from a stroke
This increased impulsivity and lack of self-control is most likely due to
disruptions between the frontal lobes
serve as the executive control center of the brain, and other parts of
the brain.
therefore → persons with extensive brain injury can retain most of their
cognitive abilities, yet lose some degree of self-control
Persons with personality changes following traumatic brain injuries often have
spontaneous outbursts, sudden changes in mood, and episodes of
aggression and can become quite disruptive to their families
e.g. Phineas Gage
****An advantage of the physiological approach is that physiological characteristics
can be measured mechanically and reliably.
physiological characteristics = functioning of organ system within the body
physiological systems
nervous system, the cardiac system, and the musculoskeletal system
All of the physiological systems are important to the maintenance of
life, and their study has resulted in the fields of medicine, anatomy, and
From the perspective of personality psychology, physiology is
important to the extent that differences in physiology create, contribute
to, or indicate differences in psychological functioning.
e.g. people differ from one another in how sensitive their
nervous systems are to stimulation
Given exposure to loud noise, for example, some people
find it quite irritating, whereas other people are not
bothered at all.
The physiologically oriented personality psychologist would say that this
person is introverted (a psychological characteristic) because he or she has
an overly sensitive nervous system (a physiological characteristic)
this approach assumes that differences in physiological characteristics
are related to differences in important personality characteristics and
behavior patterns.
The Brain Injury of Phineas Gage

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Phineas was an industrious worker, highly agreeable and conscientious, and
seen by his employers as one of their most capable and efficient foramen
The dynamite accidentally ignited and the explosion shot the iron rod out of
the hole like a bullet
The iron rod destroyed a large portion of the front part of his brain
most of his intellectual functions remained intact. However, his personality
changed dramatically.
He lacked the ability to direct himself nor could he devise plans to achieve
goals. He was impulsive and aggressive
Scholars have speculated on connections between bodily shapes and
personality traits for centuries.
However, one bodily difference that is receiving attention these days is
the ratio of the index finger to the ring finger, commonly called the
“digit ratio” index.
This ratio is easy to calculate by measuring the index and ring fingers
One common and reliable finding is that women have a higher
digit ratio than men.
Women tend to have index fingers that are longer than
their ring fingers, resulting in a digit ratio greater than 1.0,
digit ratio is determined prior to birth through exposure of the fetus to
testosterone in utero
Testosterone in utero also influences the development of the gonads and
sexual development of the fetus.
Consequently, the digit ratio after birth is thought to be a lifelong
indicator of the amount of prenatal testosterone that the fetus was
exposed to
The more testosterone exposure, the smaller the index finger relative
to the ring finger
Prenatal testosterone exposure is greater for male fetuses than
female fetuses, and hence there is a lifelong difference between
the sexes in digit ratio
However, even within a single gender, the differences in digit ratio appears
related to the kinds of personality traits hypothesized to be related to
“young male syndrome” include risk taking, a tendency toward
violence, and competitiveness.
Although males do score higher on all three of these traits than women,
research linking digit ratio to these traits is mixed.
in a study → They found a strong relationship between digit ratio and
impulsive sensation seeking (men with longer ring fingers relative to their
index fingers

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This finding is consistent with a number of other studies that found
lower digit ratio was associated with risk taking, such as participating in
riskier lotteries
Results with women tend to be less clear, though some studies have reported
that, in females, a lower digit ratio (similar to the male digit ratio) is associated
with higher levels of risk taking
Another characteristic of the physiological approach to personality is
simplicity or parsimony.
Physiological theories often propose to explain a good deal of behavior
with a few constructs.
still → Most physiologically oriented psychologists would not argue that
“physiology is destiny.” Most would agree that physiology is only one cause
among many for explaining behavior.
A Physiological Approach to Personality
Most physiological personality psychologists today focus on measures of
distinct physiological systems, such as heart rate or brain waves.
research question → whether some people will exhibit more or less of a
specific physiological response than others under certain conditions.
e.g. people who are introverted may avoid loud parties because they
easily become overwhelmed by the social and physical stimulation at
such parties
Notice that this statement specifies which particular environmental
conditions (i.e., loud parties) affect which particular personality trait
(i.e., introversion) to produce a particular physiological response (i.e.,
overwhelmed, indicated by increased heart rate), which then promotes
a specific behavioral response (i.e., avoidance).
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