PSYC 305 - L4: Determining Nature, Nurture, & Necessity

why is Steve Jobs interesting in the nature-nurture debate

- adopted

- biological parents highly educated, adoptive parents less

- has fraternal twin who is a highly educated novelist

- twin adopted into different family, but show similar creativity and intellect

- suggests genetic predisposition for traits

explain why nature and nurture are inseparable

- inseparable interaction between genes and environment

- genes expressed in specific environments, and environmental experience have effect as influence by genetic makeup

- can not measure on individually, instead do on group/population level

- focus on which is more important in explaining observed variance—genes or environment?

what is the contemporary view of nature-nurture?

majority experts agree nature and nurture play role in personality traits (pretty 50/50 with traits)

explain the 10,000 hour rule

- some extreme conclusions made about role of nature or nurture

- study ask violinists what estimate average practice

- find more accomplished estimated 10,000 while less good estimated 5,000

- suggest innate talent is actually from intense practice

- claim can be expert in anything through 10,000 hours of practice

what is the controversy of the 10,000 hour rule

- reality is lots of variability

- over half of variance in talents and abilities from genes

define heritability

observed variance of specific trait in population accounted for by genetic variance

how is heritability viewed?

not applied to individual, not constant or absolute, not precise statistic

- some circumstances affect development of genetics

- genetic differences in populations affect heritability

- not precise because rely on self-report and correlational analysis

- rate of heritability estimates varies across studies, assessments, and traits

define environmentality

proportion of observed variance in a group of individuals

attributable to environmental variance

what is the ratio of nature-nurture

greater environmentality of trait, less heritability

describe the heritability of the big 5

- meta analysis using different methods

- find average is 48% (usually fall between 40-60%)

- moderate to high

what is the heritability of Eysenck's model?

44% (moderate-high)

what is the heritability across all human traits?

studies that look at all human traits (physical, psychological, disorders) estimate 49%

what are the 2 types of environmental effects?

shared and non-shared (focus on early environments)

define shared environmental effects

family and environmental influences that affect twins or siblings similarly or don't change across child (e.g. parents religion, neighbourhood, tv time)

define non-shared environmental effects

family and environmental influences that effect twins or siblings differently (e.g. birth order, changes in parenting style, unique experiences, strictness, friends)

what proportion of variance in the big 5 is accounted for by shared experience

small amount of influence on personality, mainly from genetic variance and non-shared environment

what parts of non-shared environment are most influential?

- friend groups and social networks important role in accounting for variance in personality

- more likely based on research that numerous factors contribute (many small effects make up personality)

how does birth order influence personality?

- meta analyses find no correlation or important role in personality

- correlated with other things, but not directly related to personality (e.g, differences in parental treatment)

- extremely reliable for differences in intelligence (increasing birth order, decreasing intelligence)

- caused by decreasing parental attention and resources

what aspects of person are most influenced by shared environment?

- attitudes, religion, political orientation, health behaviours

- high correlation in behaviours like smoking and drinking

what is a limit of heritability?

heritability estimates does not account for gene x environmental interactions

what are 3 gene x environment interactions?

1. genotype-environment interaction

2. genotype-environment correlation

3. epigenetics

explain genotype-environment interaction

- difference in impact of environment depending on individual geneotype

- children who experience early abuse, may develop antisocial or psychopathic tendencies (but not all!)

- if have low MOA, more likely develop antisocial tendencies

- diathesis model

explain genotype-environment correlation

exposure to environmental conditions depends on genotype, genotype play role in what exposed to in first place

what are the types of genotype-environment correlations?

1. passive

2. reactive

3. active

define passive genotype-environment correlation

environment provided based on genes, child responsive; child not active in choosing environment (parents share genes with child so see correlation with child)

e.g. parent likes reading, genes predispose child to also have high verbal ability, parent buy books for child

define reactive genotype-environment correlation

heritable behaviour evoke environmental/social response

e.g. reactive, hot-tempered child get fewer warm responses from parent

define active genotype-environment correlation

heritable propensity to select environmental exposure

e.g. sensation seekers have genotype that predisposes trait

define epigenetics

study of changes in organisms caused by changes in gene expression due to environmental influences.

who does epigenetics work?

- changes in behaviour or trait resulting from genes and gene expression (genes happen as result from environment)

- no changes in DNA, just chemical processes from environmental events that affect how genes depressed (turn on or off)

- research find role in risk-taking, sociability, and stress reactivity

what limitations are there on epigenetics and personality?

- changes based on environment correlated with traits, but not causal (e.g. differences in neuroticism)

- directionality and causality hard to sort (could be epigenetics from environment or vice versa)

- research only focus on narrow traits, still evolving

when do epigenetics happen most

happen commonly in early life, but also in adulthood

what genes are directly linked with personality?

1. dopamine receptor gene (DRD4)

2. serotonin transporter gene (5-HTTLPR)

explain the role of DRD4 in personality

- link to novelty-seeking, extraversion, many psychiatric conditions

- relationship moderated by other traits and factors

explain the role of 5-HTTLPR in personality

link to neuroticism and depressive and anxiety traits links

why are there so few genes directly linked with personality?

- many genes involved in most traits (polygenic), nothing is 1:1 relationship

- expected because each trait is so encompassing and manifests in many different ways (narrow traits)

how do genes influence traits and behaviour?

- almost everything partially heritable, even life outcomes (e.g. divorce)

- heritability not about specific genes in outcomes, just help explain variants

- genes affect neurotransmitters, hormones, and physiological arousal, which affect thoughts, feelings, and behaviours over time (trait)

explain how personality is not human exclusive

animals differ in behaviour

luna: submissive, sensitive, affectionate, attentive, cooperative, anxious

kobe: dominant, sensation-seeking, affectionate, bold, fear-prone (scared of unusual things)

what is a challenge of studying non-human personality?

difficult to study intrapsychic domain!

describe how cleaner fish show personality

- can pass mirror recognition test and in photos

- have differences in strategies of honesty and cheating when cleaning other fish

- some steal mucus from large fish which should not

- action not random or environmental, some individuals do and do not (show individual differences in different species)

- contingency in traits

- found those more likely to steal more likely to explore

- honest fish more disciplined and clean fish better

describe how chimpanzees show personality

- often use personality to describe them

- in large sample identified 5 core traits through factor analysis (3 overlap w Big 5)

- suggest share at least 60% of traits between humans and chimps

- supports evolutionary basis of personality that extends beyond our species t

- more similar traits in closely related species

what are chimpanzee core traits?

1. reactivity

2. dominance

3. openness

4. extraversion

5. agreeableness

define evolutionary continuity

- all animal capacities and behaviours exist, to various degrees and effects, in continuity with other species

- little evidence for human exceptionalism

- different outcomes, but similar underlying outcomes

what are basis of evolution?

premise that all humans from unbroken line of ancestors who

(1) survived to reproductive age

(2) reproduced (and had offspring that also reproduced)

what are components needed for evolutionary success?

- importance of agency (individual and collective species level) and getting ahead

- also important that had to get along, passion, empathy, cooperate through communion

- depend on both to survive and flourish

which trait was most important for ancestors?

communion (cooperation is instinctive over competition)

what are the 2 goals of evolutionary success?

1. engage with others (primary)

2. pursue personal goals and distinctiveness

explain evidence for how cooperation is instinctive

see innate helping behaviour in young children and in chimps (but if reinforce behaviour then less likely to repeat it because only do with reward not of own volition, become contingent on another outcome to perform)

what are levels of analysis to consider when studying evolution of traits?

1. human nature (what are people like)

2. individual and group differences (how and why are people different)

explain human nature level analysis

traits that are most adaptive are historically present in all species

what traits are most universal?

- focus on prosocial traits (belonging, empathy)

- most universal traits relate to ability to get along (e.g., the need to belong, empathy, helping & altruism)

name examples of key universal traits

belongingness, empathy, helping and altruism

describe the importance of the need to belong

- group life important for protection and shared resources

- historically often would be dead without group (safety, scavenging)

- ties to social anxiety, fear of exclusion

describe the dynamic bonobos

e.g. aka pick me chimpanzees

- organise different from us (matriarchal)

- more peaceful and cooperative than humans and chimpanzees

- very sexual being (solve disputes by having sex)

- polyamorous and they swing both ways

- have less intergroup conflict

describe the importance of empathy

important for fortifying relationships, social bonds, trust through understanding and shared perspectives

what is animal evidence of empathy?

rhesus monkeys:

refuse to pull chain to get food if know will electric shock neighbor

chimpanzees and bonobos:

have overwhelming evidence for empathy also + morality: care for sick and disabled, contagious yawning (sign of empathy) for humans and other of same species (cross-species evidence)

describe the importance of helping and altruism

help to benefit selves, but also function of recipient ability to enhance inclusive fitness of helpers through survival, seen in any social species

define inclusive fitness

protective behaviour based on importance of survival of ones genes, including through closely-related relatives (e.g. humans more likely help siblings because help genes pass on)

what is an example of interspecies altruism?

- most seen in dolphins and whales saving other species (and humans)

- evidence of some advantage like to protect young, but sometimes none and just do (pure altruism)

what antisocial trait is likely to be evolutionary selected?

propensity for aggression and war

describe the importance of propensity for aggression and war

- we have intergroup conflicts at level not seen in other primates

- more likely fight, maybe evolved from intergroup aggression

- migrated farther than other species and more spread, which lead to more communities coming into contact and conflict

what is a genetic predisposition for propensity for aggression and war

chimps and humans have lower expression of gene that inhibits fight-or-flight (ADRA2C)

explain individual and group differences level analysis

examines how people differ from one another and how groups of people differ in their traits or behaviours

what are the 4 explanations for maintenance of variability over time?

1. environmental triggers of differences

2. frequency-dependent selection of traits

3. contingencies among traits

4. optimal variance over time and space

describe environmental triggers of differences

- from differences in early life environments that act on shared traits to produce differences throughout development

(e.g. individual differences in neuroticism may result from differences in stressors/demands in early life environments)

- childhood adversity is correlated with lower agreeableness and higher anger and aggression in adulthood

- transgenerational epigenetic mechanisms (such traits could be maintained across generations)

- from environmental effects on genes from situations

describe contingencies among traits

some traits more beneficial if occur alongside other traits, other traits (e.g., physical) may make the expression of certain psychological traits more or less adaptive.

what are examples of trait contingencies?

- quick temper may be advantageous if one is big and strong, but not if one is small and weak

- extraversion may be more advantageous for those who are both strong and physically attractive

- social dominance and narcissism may be more advantageous as social status rises

describe frequency-dependent selection of traits

- reproductive success of a trait depends on its frequency relative to other traits in a population

- as trait more common over generations, may become less successful and more predictable, often due to a social response and/or loss of competitive advantage

- if rare more advantageous relative to populations (sneaky!)

e.g. in a large population of people with cooperative dispositions, selection may favour cheaters as long as they're not too common, but when cheating becomes too frequent, it becomes more difficult (as cooperators become aware of it), and frequency of cheating goes down

what does frequency-dependent selection of traits explain?

- explains maintained psychopathy in population at low frequency

- explain 1:1 ratio of biological sex (reproduction would decline if one larger)

describe optimal variance over time and space

- different levels of a trait are optimally adaptive in different environmental conditions over time

- creates heritable differences in personality that are maintained in population

- no optimal level of trait for whole population, depend on where are

- allow balancing in selection

e.g. during food scarcity, selection favours risk-taking, during food abundance, selection favours a more cautious disposition, both become common traits in a population over time

relate optimal variance over time and space with the big 5

- no unconditionally optimal value of big 5 traits

- expect retained genetic diversity over time

- all broad traits have benefits and costs associated, depending on situation

e.g. neuroticism involves increased vigilance to danger as well as increased stress reactivity

e.g. extraversion results in higher mating success but also more risks and greater family instability and in general social bonds

where are personality differences most pronounced, and why?

highly social specials because account for adaptive niches created in social environment

- different domains where traits especially well suited (e.g. specific problems)

- need leader, services, wisdom roles all call for different traits

- humans have complex social environment

define difference-detecting mechanisms

ability to notice and remember individual differences relevant to solving adaptive problems to optimise time

when are each of the big 5 most optimal for problem-solving?

- likely to rise in the hierarchy (extraversion, dominance)

- likely to be a good cooperator (agreeableness)

- reliable and dependable (conscientiousness)

- drain resources and monopolizs time (neuroticism)

- go to for advice (openness/intellect)