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Chapter

Ch 6 Brain, evolution, and personality.pdf

3 pages86 viewsWinter 2013

Department
Psychology
Course Code
Psychology 2550A/B
Professor
Kelly Olson

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BRAIN-PERSONALITY LINKS
Genes 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 functioning
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Biological bases of extraversion-introversion
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He proposed that these differences are influenced by the ascending reticular activation system (ARAS) of the brain --> the system believed to
regulate overall arousal in the cortex
According to eysenck's theory, extraverts differ from introverts because of differences in their physiological level of arousal (LOA) in the brain
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Introverts - even small amounts of stimulation can overstimulate them physiologically --> leads to distress and withdrawal in their behaviour
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Extraverts - ARAS not easily stimulated --> leads them to seek activities that will increase the level of stimulation
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Found that introverts (compared to extraverts) show greater changes in their brain wave activity in response to low frequency tones, indicating
their lower threshold for stimulation to the CNS
While intro/extraverts dont differ in their level of brain activity at resting levels, they do differ in response to stimulat ion
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Their differences influence their performance under diff arousal levels to do them well
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Optimal level of arousal (OLA) - defined by Hebb as the arousal level that is most appropriate for doing a given task effectively and shows that too much
or too little arousal undermines performance
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Brain asymmetry and personality differences
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Brain asymmetry
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People differ consistently in the degree to which the right versus the left sides of their brains are activated - that difference is called brain asymmetry
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To study the diffs, use electroencephalograph (EEG)
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Positive measure = higher activity on right side
Negative = higher activity on right
To calculate diffs in the brains asymmetry, researchers subtract the level of EEG brain wave activity on the left side of the brain from the right side
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Stable individual dfferences found in the brains asymmetry in anterior (frontal) brain regions
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The behavioural inhibition and activation systems
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Useful for avoiding danger
Behavioural inhibition system (BIS) - causes people to withdraw from certain undesirable stimuli or punishments (thus, it inhibits behaviour) - ex,
hamlet
It facilitates approach behaviours in the search for possible gratifications and positive outcomes in the pursuit of goals
Behavioural activation system (BAS) - directs individuals toward certain desirable gals or incentives (thus activates approach behaviour)
One of these individual differences involves two neurological systems in the brain:
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Brain asymmetry and emotional reactivity
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They also showed higher levels of self-reported BAS sensitivity on questionnaires
People who had higher resting levels of activity in their left frontal area of the brain gave more positive responses to happ y stimuli
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Higher resting levels of activity in the right frontal area of the brain were indicative of more negative feelings in respons e to aversive stimuli, as well as
higher levels of self-reported BIS sensitivity on the self-report measures of reactivity to threats
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"taking mother away" study - those who cried and were more upset also tended to be the ones who characteristically have more brain wave activity on
the right than on the left side, even when they were measured during the resting stage
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Individual differences in this type of emotional reactivity seem to be a stable quality already seen in the young child
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IN FOCUS 6.1 AN EARLY EFFORT: PHYSIQUE AND PERSONALITY?
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Endomorphic (soft and round, overdeveloped digestive viscera) --> viscerotonic (relaxed, loves to eat, sociable)
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Mesomorphic (muscular, rectangular, strong) --> somatotonic (energetic, assertive, courageous)
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Ectomorphic (long, fragile, large brain and sensitive nervous system) --> cerebrotonic (restrained, fearful, introvertive, artistic)
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BIS, BAS, and personality traits
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Greater activity in the BAS seems to be more characteristic of extraverts
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Greater activity in the BIS = introversion/anxiety and to related measures of temperament beginning early in life
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BAS - associated with dominance/sensation seeking and impulsivity
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BIS - with conscientiousness/behavioural inhibition
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People who are dominantly left side active in their brains experience pleasant, positive emotions more easily when positive s timuli are encountered
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People who are dominantly right-side active are more ready to respond with negative emotional reactions and distress when they face threatening or
unpleasant events
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Focus more on the potential negative outcomes rather than on the possible gains and rewards when considering alternative action
possibilities
Individuals who are extremely reactive in the BIS tend to be especially sensitive to potential threat, punishment, and danger
People who are highly reactive in the BAS are likely to show the opposite pattern - more responsive to incentives and possible positive outcomes
In sum
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Summary and implications
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Findings on the BAS and BIS and on brain asymmetry suggest that these are specific and distinct incentive and threat systems in the brain that are
responsive, respectively, to environmental signals of reward and threat, and that are related to positive and negative mood
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There are clear and meaningful specific links between peoples' characteristic brain activities and their characteristic emoti onal and behavioural reaction
patterns to different types of positive and negative stimulation
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It is noteworthy that brain systems such as BIS and BAS are linked to personality in context -specific ways that again reflect the importance of taking
account of the relationship between the expression of personality and the characteristics of the stimulus situation
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The distinctive dispositional pattern of people high in BIS activity takes the form: if threats-punishments are encountered, then inhibition, high anxiety
distress, negative emotions
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Probing the biology of neuroticism
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These netwrosk are in the left VS right hemispheres and in the frontal VS posterior regions
Anxious emotional arousal and worry may reflect two separate neural networks in the brain
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Psych conditions that have been grouped under the term "neuroticism" may actually consist of two distinct mechanisms
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Brain, evolution, and personality
October-04-12
12:54 AM
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