Chapter 7 - Physiological Approaches to Personality.docx

Chapter 7: Physiological Approaches to Personality Personality Psychology 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 behavior. 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 physiologically. - 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 activity. 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. Main Findings: - 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 Implication: - Emotional reactivity & distress tolerance may be key to understanding self- injury. - 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 heart rate. - 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 systolic pressure. 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- flight response. - 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 scalp. - 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 negative images o Extraversion = Correlated with increased frontal brain activation to positive images 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 arousability. o i.e. Extraverts and i