PersonalityWhat is the biological basis of personality?Nearly all personality traits have a genetic componentTwin studiesshow approximately half the variance in personality is explained by genetic similarityIdentical twins become more alike as they grow older. This is not true for siblings and dizygotic twinsFamily environmentShared home environment has limited impact on personalityAdopted children have no significant personality relationship to adoptive parentsLarger, but still small, relationship between adoptive children and biological parentsBirth order is related to personalityParticular parenting style may not have a major impact on personalityTemperaments are evident in infancyTemperament: Biologically based tendencies to feel or act in certain waysThree temperament dimensions (A. Buss & Plomin)Activity levelEmotionalitySociabilityTwo temperament dimensions (Rothbart)ReactivitySelf-regulationTypes based on temperamentsThree temperament styles (Chess & Thomas)Easy children (well-adjusted)Difficult children (undercontrolled)Slow-to-warm-up children (inhibited)About 60% of children fall into these types. Other 40% are combinations.New Zealand studyClassification at age 3 predicted later personality and behaviorNeurophysiological mechanismsEysenck’s theoryCortical arousal is regulated by the ascending reticular activating system (ARAS)We seek an optimum level of arousalExtravertsChronically underarousedSeek stimulationIntrovertsChronically overarousedSeek calmMore recent workGray’s Approach-inhibition model of learningExtraverts have stronger BASIntroverts have stronger BISBIS is associated with frontal lobe activityExtraverts have more active dopamine circuits (involved in BAS)Functional approaches to personalityBig 5 each provide important info for mate selection (D. Buss)Problem: natural/sexual selection should have eliminated variationTraits not evolutionarily relevant?Social equilibriumsome traits more valuable when rareno univeral optimum; depends on peersselection creates balance among typesCan personality change?Traits remain stable over timeMost research shows traits to be very stable over timeBig Five study shows stability, but consistency increases as individuals get olderStability is in terms of ranking of individuals, not absolute scoresPeople tend to become more agreeable and more conscientious as they get olderThis pattern holds across culturesCharacteristic adaptations changeMcCrae & Costa modelBasic tendenciesDispositional traits determined by biological processesCharacteristic adaptationsAdjustments people make to situational demandsDifferent aspects of personality (stable and fluid) interact to produce behaviorThree levels of personalityStability of personality dependent on level at which you view itQuantum changeTransformation of personality that is sudden, profound, enduring, and affects a wide range of behaviorAppears to happen without effortPlays central role in life narrativesBrain injury and personality changeDamage to specific brain regions can lead to personality changesFrontal lobe damage can cause people to become more extraverted, impulsive, socially inappropriate, and moodyTemporal lobe damage can cause a person to become humorless, obsessive, paranoid, and rule-boundAlzheimer’s disease can cause a variety of surprising personality changesDrugs and personality changeSerotonin enhancing drugs can cause significant personality changesDecrease in neuroticismIncrease in extraversionIndependent of effects on depressionSSRI studyNon-depressed participantsReduction in hostilityIncrease in cooperative behaviorsPsych 301, 10/3/3PersonalityWhat is the biological basis of personality?Nearly all personality traits have a genetic componentTwin studies show approximately half the variance in personality is explained by genetic similarity Identical twins become more alike as they grow older. This is not true for siblings and dizygotic twinsFamily environmentShared home environment has limited impact on personalityAdopted children have no significant personality relationship to adoptive parentsLarger, but still small, relationship between adoptive children and biological parentsBirth order is related to personalityParticular parenting style may not have a major impact on personalityTemperaments are evident in infancy Temperament: Biologically based tendencies to feel or act in certain waysThree temperament dimensions (A. Buss & Plomin)Activity levelEmotionalitySociabilityTwo temperament dimensions (Rothbart)ReactivitySelf-regulationTypes based on temperamentsThree temperament styles (Chess & Thomas)Easy children (well-adjusted)Difficult children (undercontrolled)Slow-to-warm-up children (inhibited)About 60% of children fall into these types. Other 40% are combinations.New Zealand studyClassification at age 3 predicted later personality and behaviorNeurophysiological mechanisms Eysenck’s theoryCortical arousal is regulated by the ascending reticular activating system (ARAS)We seek an optimum level of arousalExtravertsChronically underarousedSeek stimulationIntrovertsChronically overarousedSeek calmMore recent workGray’s Approach-inhibition model of learningExtraverts have stronger BASIntroverts have stronger BISBIS is associated with frontal lobe activityExtraverts have more active dopamine circuits (involved in BAS)Functional approaches to personalityBig 5 each provide important info for mate selection (D. Buss)Problem: natural/sexual selection should have eliminated variationTraits not evolutionarily relevant?Social equilibriumsome traits more valuable when rareno univeral optimum; depends on peersselection creates balance among typesCan personality change?Traits remain stable over timeMost research shows traits to be very stable over timeBig Five study shows stability, but consistency increases as individuals get older Stability is in terms of ranking of individuals, not absolute scoresPeople tend to become more agreeable and more conscientious as they get olderThis pattern holds across cultures Characteristic adaptations changeMcCrae & Costa modelBasic tendenciesDispositional traits determined by biological processesCharacteristic adaptationsAdjustments people make to situational demandsDifferent aspects of personality (stable and fluid) interact to produce behaviorThree levels of personalityStability of personality dependent on level at which you view itQuantum changeTransformation of personality that is sudden, profound, enduring, and affects
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