Chapter 7: Physiological Approaches to Personality
February 7, 2012
- An advantage of the physiological approach is that physiological
characteristics can be measured mechanically and reliably.
- Physiological characteristics refers to the functioning of organ systems
within the body.
- Examples of Physiological Systems are:
o Nervous system (brain and nerves)
o Cardiac system (heart, arteries, and veins)
o Muscuskeletal system (muscles and bones, which make movements
and behaviors possible)
- All of these systems are important to the maintenance of life.
- Physiology is not “destiny” but just one of the many causes for explaining
Building a Theoretical Bridge
- A theory specifies which conditions or stimuli will interact with which
personality traits to produce specific responses, which can be observed
- Connections between environmental conditions (loud parties), personality
traits (introversion), psychological responses (overstimulation), and
physiological indicators (increased heart rate) build a theoretical bridge that
links personality to specific situations in terms of evoking a certain
psychological response (avoidance), which can be identified and measured
using physiological measures.
Common Physiological Measures Used in Personality Research
- Most of the common physiological measures in personality research are
obtained from electrodes.
- Electrodes: sensors placed on the surface of a participants skin. They do not
penetrate the skin. A drawback of this measure is that the participant is
hooked up to a machine so movement is constrained.
- Telemetry: (newer generation of electrodes) a process by which electrical
signals are sent from the participant to the poly gram through radio waves
instead of by wires. Being used by astronauts.
1. Electrodermal Activity (Skin Conductance)
- Skin of palms of hands (and soles of feet) contains a high concentration of
sweat glands, which are influenced by the sympathetic nervous system, the
branch of the autonomous nervous system that prepares the body for action. - When the sympathetic nervous system is activated (episodes of anger,
anxiety, startled) the sweat glands begin to fill with salty water.
- And because water conducts electricity, this process (electrodermal activity)
makes it possible for researchers to measure sympathetic nervous system
Nock & Mendez Experiment
Skin conductance & Self-injury
- 2 groups of people, one group had history of self-injury and the other did not.
- They induced stress in these people by giving them a matching game where
even correct answers were given negative feedback.
- Goal was to determine how long people stay in the game and tolerate distress
of negative feedback.
- Individuals with a history of self-injury have elevated skin conductance &
more negative emotional reactivity to stress
- Individuals who self-injured also quit the game sooner which also might
indicate lower distress tolerance
- Emotional reactivity & distress tolerance may be key to understanding self-
- Some people showed skin conduction responses even in the absence of
external stimuli. These people have the personality traits of anxiety and
neuroticism. These people have sympathetic nervous systems that are in a
state of chronic activation.
2. Cardiovascular Activity
- Examples of measures of cardiovascular activity include blood pressure and
- Blood Pressure is the pressure-exerted by the blood on the inside of the
artery walls and it is typically expressed with two numbers: diastolic and
o Systolic Pressure: refers to the maximum pressure within the
cardiovascular system produced when the heart contracts.
o Diastolic Pressure: refers to the resting pressure inside the system
between heart contractions.
- Blood Pressure can increase when the heart pumps larger strokes generating
more volume or through a narrowing of the artery walls. These actions occur
through the activation of the sympathetic nervous system in the fight-or-
- Common measure of stress response.
- Heart Rate is usually expressed in Beats per Minute (BPM)
o i.e. interval between beats - Good indicator of stress/anxiety, cognitive effort
- Cardiac Reactivity: The increase in BP & heart rate in times of stress
- Cardiac Reactivity has been related to Type A personality (a behavior
pattern characterized by impatience, competitiveness and hostility.
- Chronic cardiac reactivity contributes to coronary artery disease.
- The relation between cardiovascular reactivity and Type A is one example of
how physiological measure have been used in the study of personality.
3. Brain Activity
- Electroencephalogram (EEG): a technique used to measure the small
amounts of electricity that the brain produces by electrodes placed on the
- EEG recordings can be obtained for various regions of the brain while the
participant is asleep, is relaxed but awake or is doing a task.
- These measures of regional brain activity can provide useful information
about patterns of activation in various regions of the brain, which may be
associated with different types of information processing tasks.
- fMRI: is an imaging tool, which was developed primarily of medical diagnosis
allows physicians and researchers to look inside the working brains of their
patients. This tool can show what parts of the brain are active while the
person is performing a task.
- Canli Experiment (2001): used fMRI to scan the brains of people as they
looked at 20 negative pictures and 20 positive pictures and they found that
personality correlated with the degree of brain activation in response to the
positive and negative pictures.
o Neuroticism = Correlated with increased frontal brain activation to
o Extraversion = Correlated with increased frontal brain activation to
Physiologically Based Theories of Personality
Extraversion & Introversion
- Eysenck’s Original Theory:
o He proposed that introverts are characterized by higher levels of
activity in the brain’s ascending reticular activating system (ARAS)
than are extraverts.
o ARAS is a structure in the brain stem thought to control overall
cortical arousal. (Gateway’ for nervous stimulation of cortex)
o Introversion = Higher resting cortical arousal (ARAS lets in too much)
o Extraversion = Lower resting cortical arousal (ARAS lets in too little)
- Eysenck’s Revised Theory:
o Introverts and extraverts are not different at resting levels, but are
different under moderate levels of stimulation. o The real difference in introverts and extraverts lies in their
o i.e. Extraverts and i