Biological Approaches to Personality Week 5 PDF

Biological/Evolutionary Perspectives PS338 Dr Jenny Groarke University ofGalway.ie Two Aspects of the Brain that Can Be Examined with Technology Anatomy: functions of parts of the brain Biochemistry: effects of neurotransmitters and hormones on brain...

Biological/Evolutionary Perspectives PS338 Dr Jenny Groarke University ofGalway.ie Two Aspects of the Brain that Can Be Examined with Technology Anatomy: functions of parts of the brain Biochemistry: effects of neurotransmitters and hormones on brain processes Both are related to personality and behavior. Research Methods for Studying the Brain Brain damage Phineas Gage Lesions Brain stimulation Mostly animals, but also people while conscious Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS)  Research Methods for Studying the Brain Brain activity and imaging Used to observe functioning directly Detect WHEN the brain is working o Electroencephalography (EEG) o Magnetoencephalography (MEG) Detect WHAT PARTS of the brain are working Computed tomography (CT) scans Positron emission tomography (PET) Functional Magnetic Resistance Imaging (fMRI) Research Methods for Studying the Brain Difficulties with imaging techniques: All parts of the brain are always active to some degree. o Blood oxygenation level dependent (BOLD) imaging signals and perfusion imaging Brain activity in response to a stimulus does not mean the same psychological process occurs every time that area is active. Most researchers only look at small areas. o Difficult to detect the neural context effect Difficult and expensive Personality and the Brain The Amygdala Links perceptions and thoughts with emotional meaning Role in negative and positive emotions Role in assessing whether a stimulus is threatening or rewarding Relevant traits: anxiety, fearfulness, sociability, sexuality Relevant for motivation o Whitman murders at University of Texas in 1966 The Frontal Lobes and the Neocortex Higher cognitive functions The frontal lobes and emotion o Pleasant emotions (left) and unpleasant emotions (right) o Approach (left) and withdrawal (right) o Inhibition of reactions to unpleasant stimuli (left) o Emotional stability (left) and neuroticism (right) o Propensity to get angry (left) The Frontal Lobes and the Neocortex (2) Social and emotional understanding Self-control and regulation of impulses and feelings Case studies o Phineas Gage (1848) o Elliott Somatic marker hypothesis The Anterior Cingulate Important for experiencing normal emotions Controlling emotional responses and behavior impulses o Charles Whitman Possible implications for positive and negative affective differences between extraversion and neuroticism Brain Systems “Nearly everything in the brain is connected to everything else” Persistence = frontal cortex and striatum C-system (lateral PFC, hippocampus, medial temporal lobe, posterior parietal cortex) and X-system (vmPFC, amygdala, lateral temporal cortex) Neural context effect The Biochemistry of Personality Galen (Rome, A.D. 130–200) proposed that personality depended on the balance of humors (blood, black bile, yellow bile, phlegm). The chemistry of the mind o Neurons communicate with neurotransmitters. o Hormones stimulate or inhibit neural activity. The Biochemistry of Personality Central nervous system Peripheral nervous system Endorphins Chemicals make up neurotransmitters; enzymes break them down. Eysenck’s Biological Basis of Personality » Hans Eysenck first to link personality to biological functions (in modern times) » PEN theory Eysenck’s Biological Basis of Personality Introverts are quiet and retiring… Extraverts are outgoing, uninhibited, and immersed in social activity… Eysenck (1967, 1981) argued these differences are based on differences in activation of the cerebral cortex Biological explanations of personality Eysenck (1967, 1981) argued differences between extraverts and introverts are due to differences in activation of the cerebral cortex ARAS – Ascending Reticular Activating System Low ARAS resting activity = extraversion (less sensitive) High ARAS resting activity = introversion (more sensitive)  Eysenck’s Biological Basis of Personality ‘Introverts are characterized by higher levels of activity than extraverts, and so are chronically more aroused than extraverts’ (Eysenck & Eysenck, 1985)  Eysenck’s Biological Basis of Personality Extraverts easily get bored (under-aroused) and so need to seek out more environmental stimulation – don’t have enough Introverts are constantly over-aroused by outside stimuli – need peace and quiet – have too much stimulation  Eysenck’s Biological Basis of Personality Drug effects: Introverts higher cortical arousal need less stimulation, but need more of a depressant drug to reach a level of non-alertness (Eysenck, 1983) Extraverts seek stimulation – consume significantly more stimulating foods/beverages (coffee, chocolate, etc.)  http://www.bbc.com/future/story/20160420-what-can-a- The lemon juice test lemon-tell-you-about-your-personality Introverts produce more saliva (i.e., react more strongly) to lemon juice  Eysenck’s Biological Basis of Personality Neuroticism; Arousal related to the sympathetic nervous system (origin in spinal cord, relating to ‘fight or flight’ stress responses) Neurotic – low arousal thresholds (takes little to stress them out) Emotionally stable – high arousal thresholds (more difficult to stress out) Hormones: Epinephrine and Norepinephrine Hormones Gonads Adrenal cortex Epinephrine and norepinephrine Released in response to stress to create the fight-or-flight response Females might respond differently to stress. o Tend-and-befriend Only the initial and automatic response to stress  Eysenck’s Biological Basis of Personality Psychoticism; Related to testosterone levels Associated with aggression and criminality – most criminals male Hormones: Testosterone Testosterone Concentration in men is about 10 times higher than in women Link with aggression is complex Fatherhood temporarily lowers testosterone. Levels in men lower after marriage and rise after divorce Role in control and inhibition of aggression and sexuality Related to many other behaviors Also related to behavior in women Unknown causal direction Hormones and Personality: Testosterone Basic template for the human body is the female sex. XX:XY Males have higher testosterone than females from week 8 to week 24 (gestation), from 1 st to 5th month after birth, and after puberty (LeVay, 1993) Testosterone is an essential hormone for development Hormones like testosterone believed to also change the brain which results in behavioural differences Hormones and Personality: Testosterone Early (including prenatal) exposure to hormones can influence later behavior Mothers were treated with synthetic hormones (that act like testosterone) for complications during pregnancies (Reinisch, 1981) 11 years after exposure, Reinisch (1981) collated data regarding children's decisions in situations involving interpersonal conflict Hormones and Personality: Testosterone Seventeen females and eight males exposed to synthetic progestins during gestation showed: There were no differences in verbal aggression (or IQ) between sex-matched exposed and unexposed siblings. Exposed females and males a significantly higher potential for physical aggression than their sex-matched unexposed siblings. Exposure to androgen-based compounds appeared to be most closely associated with aggressive responses. Neurotransmitters: Dopamine Dopamine Involved in responding to rewards and approaching attractive objects and people Related to sociability, general activity level, and novelty seeking Facilitates exploration, approach, and learning Associated with extraversion and openness Possible relation with bipolar disorder and impulsivity Activates the behavioral activation system (BAS) Individual differences in development of neurons that produce and are responsive to dopamine Related to the fundamental personality dimension of plasticity Neurotransmitters: Serotonin Role in inhibition of behavioral impulses Prozac: a selective serotonin reuptake inhibitor (SSRI) Physical effect: increases serotonin levels Psychological effects: controversial o Positive effects o Changes in personality for people without a diagnosed disorder o Makes negative emotions less severe without affecting positive emotions Related to the fundamental personality dimension of stability Biological explanations of personality – Gray (1987) 32 Gray's Biological Basis of Personality Anxiety [Anx] Impulsivity [Imp]  Gray's Biological Basis of Personality Reinforcement sensitivity theory (2000) 1. BAS: Behavioural Activation system (DA) ‘the reward system’ Approach behaviour and anticipatory pleasure Brain regions regulating arousal: cerebral cortex, thalamus, striatum 2. BIS: Behavioural Inhibition system (5HT) ‘the punishment system’ Avoidance behaviour Brain regions regulating arousal: brain stem, neocortical projections to frontal lobe 3. FFFS: Fight-flight-freeze system (NAd) ‘the threat system’ Sympathetic nervous system Behavioral Genetics Addresses how personality traits that differ among individuals are passed from parent to child and shared by biological relatives Examines how genes influence broad patterns of behavior  Activity THINK: Are there aspects of your personality that are inherited (i.e., that you share with family members)? To what extent do you believe personality is genetic? SHARE: Anonymously via Padlet  Twin Studies To examine how phenotypes may be attributed to variation in genotypes Compare similarity in personality between people who are and are not related and people who are related to different degrees oMonozygotic (MZ) versus dizygotic (DZ) twins Calculating Heritability Heritability coefficient  Biological basis of personality: Genetics Twin studies allow for examination both environmental influence and genetic influence MZ twins share nearly 100% of their genes DZ twins share approx. 50% of their genes Shared environment versus unique (non-shared) environment effects  Biological basis of personality: Genetics Eysenck and Prell (1951) 25 sets identical, 25 sets non-identical Neuroticism: r =.85 correlation for identical twins; r =.22 correlation for non-identical twins  Biological basis of personality: Genetics Minnesota Twin Family Study started in 1979 (Longitudinal) Followed identical and fraternal twins who were separated at an early age (and adopted) – significant genetic influence on variables like religiosity and social attitudes  Biological basis of personality: Genetics Research has examined the heritability of the ‘Big Five’ personality dimensions and their facets (Jang, Livesley, & Vernon, 1996) The genetic and environmental affects of personality assessed using 123 pairs of MZ and 127 DZ twins.  Biological basis of personality: Genetics Findings were consistent with previous research that have identified broad genetic influence on ‘Big Five’ Genetic influence was estimated at the following percentages; Neuroticism (41%) Extraversion (53%) Openness (61%) Agreeableness (41%) Conscientiousness (44%) Genes important – does environment explain the rest? The role of randomness in individual development ‘We all share a genetic program for making a human brain, and the program for making a brain like yours is specifically encoded in your DNA. But, as Mitchell explains, the way that program plays out is affected by random processes of development that manifest uniquely in each person, even identical twins"  Jean Baptiste Lamarck (1744-1849) French Naturalist Strong influence on multiple areas in science Theory of ‘inheritance of acquired characteristics’ (direct inheritance of characteristic developed over parent’s lifetime)  Jean Baptiste Lamarck (1744-1849) Example; as trees began to grow taller, giraffes responded to the change by growing/stretching longer necks so they could continue to feed The change was permanent as long as the new environmental conditions continued to apply All acquired characteristics are inherited to the next generation and does not consider struggle for existence  Charles Darwin (1809-1882) British naturalist and geologist Studied medicine (briefly) at University of Edinburgh where brother and father had studied Graduated from University of Cambridge with ordinary degree, but did not progress into theological training  Darwin and Natural Selection Variation can be seen in a species This variation is due to genetic differences Certain genes are more adaptive in certain environments Genes that ensure survival (useful variations) are passed on to children Natural Selection = the process by which characteristics that favour survival and reproduction are more likely to be passed down to offspring and future generations, therefore being retained or developed in the species as a whole. Natural Selection Mans best friend? Early humans selected and bred dogs that could be useful for different tasks Strong -> pulling loads Smart -> hunting Neglected those that did not have adaptive characteristics Natural Selection Breeders today aim to reproduce aesthetic or temperament characteristics Labradoodle – placid nature of a lab with the hypoallergenic coat of a poodle Natural Selection Domestication of animals is illustrative of the process However, in natural selection there is no breeder The idea ’selected’ is just a metaphor Natural Selection example Natural Selection Phenotype [observable characteristics] may or may not be adaptive Genotype [genetic information underlying phenotype] that is passed on. “survival of the fittest” …. genes  Natural Selection Mutations/errors in the duplication of genes [‘recipe’] lead to variation Natural Selection 1. Genotypic variation is introduced into a species via mutations in inherited genes 2. Phenotypic variations that emerge from this genetic variation result in differences in adaptive fitness, and 3. Greater adaptive fitness translates into greater likelihood of survival and reproduction, and thus greater likelihood of genetic transmission to the next generation Why does personality exist? Buss, D. M., & Hawley, P. H. (Eds.). (2010). The evolution of personality and individual differences. Oxford University Press. Evolutionary accounts of Personality Do personality traits contribute to adaptive fitness? Extraversion -> CNS that motivates us to pursue rewards [food, sex] -> adaptive fitness. But why would variation in traits/individual differences in motivational systems be favoured by natural selection.  Environmental Contexts Why have millions of years of evolution not eliminated genetic variation in all personality traits, favouring a unique, most adapted one?  Environmental Contexts Environmental contexts favour certain personality profiles over others If true, then we should find whole populations living in particular environments, sharing common personality profiles Effects of culture, geography, and language is difficult to control for  Evolutionary psychology perspective Assumes genetic basis for behaviour (but also room for environmental influences) Has primarily focused on survival, mating strategies, kinship, altruism etc. (global) – narrow – what about personality? Research in the area is growing quickly Evolutionary perspective on personality Nettle (2005; 2006) Trade off/cost-benefit of personality traits. Extraverts have more sexual partners, but also more life threatening accidents Introverts more likely to live long enough to reproduce, but extraverts who did survive to reproductive age had more offspring Evolutionary perspective on personality Penke, Denissen & Miller (2007) Personality traits are not trivial Indirectly linked to adaptive fitness via health, life expectancy, reproductive success Balancing selection = both ends of the continuum offer adaptive fitness in different ways or under different circumstances. Evolutionary perspective on personality Balancing selection = both ends of the continuum offer adaptive fitness in different ways or under different circumstances. “the early bird gets the worm, but the second mouse gets the cheese. An environment that has worms in some places but mousetraps in others could select for a mixture of go-getters and nervous nellies” (Pinker, 2009) David Buss “Theoretically, individual differences are also profoundly important. Individual differences are pivotal to the vast majority of social adaptive problems. Consider selecting a mate. Constants simply do not count. No woman ever thought ‘‘Wow, this guy is really attractive—he has an opposable thumb, walks bipedally, and speaks a language.’’ Species-typical characteristics become invisible when solving the adaptive problem of mate selection. Only differences between individuals count—in attractiveness, intelligence, dependability, health, agreeableness, ambition, empathy, and so forth.” (Buss, 2009) Evolutionary psychology perspective Frequency-dependent selection Individuals compete for a resource using one of two strategies (Maynard Smith, 1982). 1. Hawks compete aggressively and never give in until injured or opponent backs down 2. Doves give in as soon as they encounter any aggression Evolutionary psychology perspective Frequency-dependent selection Hawks always beat doves -> so should drive doves out of population, but social landscape would be constant aggression Doves always share with other doves -> social utopia, but perfect for a rogue hawk to exploit. Neither is an Evolutionarily Stable Strategy Psychopathy – Neuroticism, frequency in the population is NB  Points to remember about personality… Personality traits are naturally selected and have evolved as strategies to solve adaptive problems (Buss, 2009) Should a personality trait be adaptive, variance within the trait would be reduced to null Variance exists due to the difficulties selecting a trait that is adaptive in all contexts across evolutionary time But, Most biological differences within a species are random variations, not adaptations Humans are all members of a species that have evolved across millennia This raises possibility that ancient evolution processes have an influence on present day behaviour/personality expression This thought is tied to several labels, such as sociobiology and evolutionary psychology  Sociobiology - Altruism Sociobiologists have predominantly focused on the question of how behaviour patterns might become ‘built in’ Altruism a tendency to act for the welfare of others, to the point of sacrificing one’s own well-being, potentially one’s life, for another Altruism would appear to mean a biological or evolutionary disadvantage  Sociobiology - Altruism Is the process of evolution solely a matter of individual survival? Altruistic behaviour genetically based People more altruistic to those in their kinship group than strangers (Burnstein et al., 1994)  Sociobiology - Altruism Beyond reproducing yourself, genes are helped along to next generation by anything that helps your part of the gene pool reproduce (inclusive fitness; Hamilton, 1964) Helping/saving relatives (even in face of death), helps aspects of your genetic makeup be passed on because your relatives resemble you genetically (kin selection) Environment of Evolutionary Adaptiveness (EEA) Term first used by John Bowlby (attachment theory) Means the environment to which a species is adapted Animals that lived in different environments or survived in different ways faced different reproductive problems (hence not all the same) Throwback to past adaptive conditions – may not be so adaptive now (e.g. sugar, fat, stress response) Beware: Biological Reductionism ….a theoretical approach that aims to explain all social or cultural phenomena in biological terms, denying them any causal autonomy…  Biological Reductionism Numerous claims regarding sex differences, such as examples below: Mathematical ability Verbal skills Temperament Emotionality Aggression in all contexts Promiscuity in sexual behaviour Leadership effectiveness Moral reasoning Self-esteem Conscientiousness  Biological Reductionism All claims are unfounded once the research data is scrutinised (Hughes, 2016) gender differences in mathematical performance of 3 million people – effect size of d =.05 (Hyde, Fennema, & Lamon, 1990) Equates to a difference of 0.06 per cent, meaning 99.94 percent of the variability of the data was down to things other than gender  Biological Reductionism Large scale personality studies sometimes report sex differences in neuroticism and agreeableness (Costa, Terraciano, & McCrae, 2001) Most data gathered from US adults, showing some sex differences not consistent across countries, and non-existent in some Due to sex variances across countries suggests they are more the result of cultural contexts rather than intrinsic differences between the sexes – social influence APA statement on sex ‘differences’ https://www.apa.org/research/action/difference.aspx Problems with evolutionary psychology approaches? Post-hoc reasoning Personality very complex and individual Complete assessment directly from genes will not occur soon Highly speculative