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Chapter 7

Chapter 7

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University of Guelph
PSYC 2740
Stephen Lewis

Chapter 7: Physiological Approaches to Personality  Elliot – personality was changed after he had small brain tumor removed from front of his head - Increased impulsivity and lack of self-control can be caused by disruptions between frontal lobes which are executive center of the brain  Phineas Gage – foreman, iron rod went up through left check below cheekbone, through left eye, and out top of skull – changed his personality, became aggressive and impulsive, disregarded social conventions etc.  Physiological characteristics (functioning of organ systems within the body)can be measured mechanically and reliably  Physiological systems - Nervous system (brain and nerves) - Cardiac system (heart, arteries, veins) - Musculoskeletal (muscles and bones that make all movement/behavior possible)  Differences in in physiological characteristics are related to differences in important personality characteristics and behavior patterns A Physiological Approach to Personality  Specific statements about what traits are connected to which physiological reactions under which conditions or in response to which stimuli  Need to build theoretical bridge between personality dimension of interest and physiological variables in order to use physiological concepts to help explain personality Physiological Measures Commonly Used in Personality Research  Most obtained from electrodes – sensors placed on surface of participants skin  Before had to be hooked up to machine but now use telemetry – electrical sent to polygraph through radio waves  3 physiological measures particular interest 1. Electrodermal activity (skin conductance of electricity) - Sweat glands on feet and hands influenced by sympathetic nervous system – part of the autonomic nervous system that prepares body for action (fight or flight) - When system is activated (anxiety, startle or anger)sweat glands fill with salt water, if reaction is strong, sweat spills over creating sweaty palms – before visible can be detected with small amount of electricity - Electrodermal activity or skin conductance is when water from glands conducts electricity - Place 2 electrodes on palm of one hand, low voltage of electricity put through one, measure how much comes through at other – difference tells how well skin is conducting electricity – more sympathetic nervous system activity, the more water produced, the better skin conducts electricity - Electrodermal responses can be from a bunch of stimuli (ex. pain, emotion, sudden noises etc.) – phenomenon of interest is absence of external stimuli - Anxiety, neuroticism associated with nonspecific electrodermal response – sympathetic nervous system in state of chronic activation 2. Cardiovascular measures - Blood pressure = pressure exerted by blood on inside of artery walls, expressed in diastolic and systolic pressure - Systolic – larger number, maximum pressure within cardiovascular system produced when heart muscle contracts - Diastolic – smaller number, resting pressure inside system between heart contractions - Blood pressure can increase in number ways – heart may pump larger stroked generating more volume or artery walls may narrow – both happen through activation of sympathetic nervous system during flight/fight response - Heart rate (beats-per-minute/BPM) can measure time interval between beats (beat-by- beat) if interval is exactly one second heart rate is 60 BPM - As heart rate increases indicates person’s body is preparing for action –fight/flight - Cardiac reactivity – increase in blood pressure and heart rate during times of stress, associated with type A personality (impatience, competitiveness, hostility) and may contribute to coronary artery disease 3. Activity in the brain - Electroencephalogram (EEG) – brain spontaneously produces small amounts of electricity, which can be measured by electrodes placed on the scalp – can provide useful information about patterns of activation in different regions of brain that may be associated with different types of information processing tasks - Evoked potential technique – brain EEG is measured but participant given stimulus (tone or flash of light) and response to stimulus is assessed - Functional magnetic resonance imaging (fMRI) – non-invasive imaging technique used to identify specific areas of brain activity, as parts of brain are stimulated, oxygenated blood rushes to activated area, resulting in increased iron concentrations in blood, it detects these concentrations of iron and prints out colourful images indicating which part of brain is used to perform tasks - Personality correlated with degree of brain activation in response to positive and negative images – neuroticism correlated with increased frontal brain activation to negative images, extraversion to positive images Other Measures  Biochemical analysis of blood and saliva - Ex. from saliva can tell how competent someone’s immune system is - Immune system functioning may go up/down with stress or emotion - Ex. hormones can be extracted from saliva (testosterone which has been linked to uninhibited, aggressive, risk taking behavior patterns)  Monoamine oxidase –enzyme found in blood known to regulate neurotransmitters (chemicals that carry messages between nerve cells) – may be causal factor in attention seeking Physiologically Based Theories of Personality Extraversion-Introversion - Eysenck  Introverts characterized by higher levels of activity in brain’s ascending reticular activating system (ARAS)  Structure in brain stem thought to control overall cortical arousal – thought responsible for differences between introverts and extroverts  ARAS thought of as gateway which nervous stimulation entered cortex, if gate was somewhat closed, resting arousal level of cortex would be lower, if more open, arousal level would be higher  Introverts – higher resting levels because ARAs let in too much stimulation, have introverted behaviors because have to keep already heightened level of arousal in check (extroverts were considered the opposite, need to increase their levels)  Hebb’s theory of “optimal level of arousal” incorporated – level t
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