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Ch 6 Brain, evolution, and personality.pdf

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Western University
Psychology 2550A/B
Kelly Olson

Brain evolution and personalityOctober04121254 AMBRAINPERSONALITY LINKSGenes do not directly influence behaviour they influence behaviour through their effects in shaping our body particularly in our brain and the large number of specialized chemical components that regulate their functioningBiological bases of extraversionintroversionAccording to eysencks theory extraverts differ from introverts because of differences in their physiological level of arousalLOA in the brainHe proposed that these differences are influenced by the ascending reticular activation system ARAS of the brainthe system believed to regulate overall arousal in the cortexIntroverts even small amounts of stimulation can overstimulate them physiologicallyleads to distress and withdrawal in their behaviourExtraverts ARAS not easily stimulatedleads them to seek activities that will increase the level of stimulationStudyFound that introverts compared to extraverts show greater changes in their brain wave activity in response to low frequencytones indicating their lower threshold for stimulation to the CNS While introextraverts dont differ in their level of brain activity at resting levels they do differ in response to stimulationTheir differences influence their performance under diff arousal levels to do them wellOptimal level of arousalOLA defined by Hebb as the arousal level that is most appropriatefor doing a given task effectively and shows that too much or too little arousal undermines performanceBrain asymmetry and personality differencesBrain asymmetryPeople differ consistently in the degree to which the right versus the left sides of their brains are activated that difference is called brain asymmetryTo study the diffs use electroencephalograph EEGTo calculate diffs in the brains asymmetry researchers subtract the level of EEG brain wave activity on the left side of thebrain from the right sidePositive measurehigher activity on right sideNegativehigher activity on rightStable individual dfferences found in the brains asymmetry in anterior frontal brain regionsThe behavioural inhibition and activation systemsOne of these individual differences involves two neurological systems in the brainBehavioural inhibition system BIS causes people to withdraw from certain undesirable stimuli or punishments thus it inhibits behaviour ex hamletUseful for avoiding dangerBehavioural activation system BAS directs individuals toward certain desirable gals or incentives thus activates approach behaviourIt facilitates approach behaviours in the search for possible gratifications and positive outcomes in the pursuit of goalsBrain asymmetry and emotional reactivityPeople who had higher resting levels of activity in their left frontal area of the brain gave more positive responses to happy stimuliThey also showed higher levels of selfreported BAS sensitivity on questionnaires Higher resting levels of activity in the right frontal area of the brain were indicative of more negative feelings in response to aversive stimuli as well as higher levels of selfreported BIS sensitivity o
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