Personality Flashcards
Recap some human personality basics
How would you define human personality?
We tend to refer to consistent individual differences in people’s behaviour and cognition and those differences are quite stable across time. So if you measure personality in someone’s day and then weeks, months or even years later, you tend to get a similar answer. And people’s personality is also relatively stable in different contexts. For example, a person tends to behave in line with their personality when it comes to their social interactions in regard to friends, work, colleagues, partners. Aspects of someone’s personality could even predict which life events they’re likely to experience (marriage, divorce, imprisonment etc).
We know from studying twins, siblings, half-siblings, parents, and offspring that personality traits are partly genetically inherited. But we also know that experience, particularly perhaps in early life, plays a role in shaping personality.
How can Psychologists measure human personality?
We most often measure personality in humans using self-report questionnaires. The scores on these correlate quite well with scores made by people who know that person well and with direct observations of people’s behaviours.
What causes people’s personalities to vary?
Scientists have found some differences in underlying physiology and brain structure or chemistry (neurological) that correlate with people’s personality traits. And in humans, a lot of research finds that measures of personality traits tend to boil down to five key dimensions. That five factor model of the so-called Big Five; extraversion, neurotisicm, conscientiousness, agreeableness, and openness.
What is animal personality and how can we measure it?
definition of animal personality:
Individual differences in behaviour and/or cognition that are consistent within the individual over time and across contexts.
Also referred to as “coping style”, “temperament”, “behavioural syndrome”
Personality appears to be a widespread phenomenon in the animal kingdom.
Studies of personality variation in over 200 species, from insects to mammals.
Often includes variation in aggression, risk-taking and responses to stressors.
Example 1 - Stickleback personality:
Huntingford (1976) described consistent differences in boldness-aggressiveness in three-spined sticklebacks.
•Males differed in aggressiveness to territorial intruders during the breeding.
•Aggressiveness was consistent towards different types (species) of intruders.
•Aggressive males also bolder towards a predator (e.g. pike fish).
Boldness-aggression syndrome
= positive correlation between individual differences in boldness (responses to predators, exploring novel environments) with levels of aggression towards conspecifics. Found in blue tits, squid, spiders, snakes…
Example 2: Great tit personality
Verbeek et al. 1994.
Measure 1: Exploration in a novel environment (at age 4-5 weeks)
Measure 2: Foraging flexibility
Measure 3: Exploration of a novel object (at 9 and 18 weeks old)
Within-individual consistency in behaviors. Birds reactions to the 2 novel objects correlated between them. indicating that this behaviour is consistent in the same individual and also consistent over time. Birds reaction to novel objects at 9 and 18 weeks old correlated and was consistent across contexts.
Birds which were faster to explore novel environment formed more rigid foraging habits and approached novel object faster (and more aggressive).
Example 3 - Great apes:
in orangutans, Weiss et al. (2006) asked human caregivers of captive animals to rate individual orangutans against 48 personality descriptors. then they used principle component analysis to see how these different ratings group together, rather like the approach that is seen in humans which has led to the 5 factor model of personality. like in humans, their analysis yielded 5 reliable personality factors which they termed extroversion, dominance, neuroticism, agreeableness and intellect.
the authors found no factor that was analogous to human conscientiousness. a simular approach of people who know the animals well has been used on chimps and several other species of primates. in zoo chimps, Weiss et al. (2006) found a chimp specific factor that was related to dominance and five other factors that resemble dimensions in the human 5 factor model. these researchers suggest that analogues of human chimpanzee and organutans personality domains existed in some common ape ancestor.
they also did what was a kin to cross-cultural studies of human personality in chimps getting animal keepers in a zoo and in a separate wildlife sanctuary in a different country to rate their chimps. they found the same sex underlying factors of chimp personality in both situations. similar approaches have been applied in a range of mammals often in zoos but sometimes in the wild and also in pet animals. this is having familiar observers such as keepers, researchers or owners, rate their animals according to questionnaire items that consist of a list of adjectives such as curious or descriptions of behaviours such as subject often touches new object at great length. they statistically then boil these down with principal component analysis to find the underlying factors of personality dimensions.
the number of dimensions coming out seems to vary between species and personality constructs of animals. personality constructs of animals also vary in their degree of similarity to the human 5 factor model. for example, the neurotisicm dimensions in orangutans, in contrast to dominance in chimps. but the fact that there is seemingly consistent personality type variations across several dimensions seems to be a common finding across a wide range of species.
The overlap in personality structure across diverse species suggest that selective pressures such as those related to group structure, terrestrial lifestyles, having certain morphology or brain structure, or having social learning arent necessarily for particular personality domains to evolve
Summary:
Individual differences in behaviour that are consistent/stable over time and contexts are common across a wide range of animal taxa.
Existence of personality variation and overlap in personality structure across diverse species suggests selective pressures leading to personality evolution (or certain dimensions) may be quite general
Measuring personality:
1. Behavioural tests or test-batteries (‘Biological personality field approach’)e.g. sticklebacks, great tits…. ants, squid, octopus – and many more!
- Observers using rating scales for traits (‘Psychological personality field approach’)e.g. great apes, hyenas, cats, dolphins… macaques, dogs – and many more!
Mechanistic explanations for animal personality variation
Example 1: Great tit personality –is there genetic variation?
Consistent individual behavioural & physiological differences in their responses to mildly stressful events. how they explore a new environment or react to a novel object was strongly correlated within individuals over time.
researchers has termed these responses shy and bold personality types, also sometimes called fast or slow explorers.
the researchers noticed that groups of siblings showed similarities in the outcome of these behaviour tests.
the researchers decided to investigate further, was it because of shared early life experiences or through genetics?
they started a bi-directional artificial selection experiment using wild caught great tits that they had reared in the lab. when the birds were about 40 days old, they tested them in the novel environments and with a novel object, and they used the combined scores as a measure of their bold or shy personality.
then they mated the nine pairs of birds that scored highest in boldness with each other, and did the same with shy partners. they then fostered the chicks to new parents, creating foster families that contained a mixture of chicks from bold or shy pairings.
They did this so that they could rule out an effect of shared environments rather than inherited genes on birds subsequent personality as adults. when the chicks were fledged and then tested them and again allocated them their mates based on their personality scores. they did this over 4 generations
they found strong effects of the artificial selection on personality. each generation from the two selection lines diverged in their average boldness scores. the mean boldness score of the birds increase over the 4 generations., meanwhile the mean score for boldness of the shy birds decreased over the 4 generations.
they used their data to calculate the heritability of personality scores. Heritability (h2): 54 % of the variation in personality between individuals attributed to genes.
Drentet al. 2003.
Can we identify specific genes?
•Polymorphisms in several neurotransmitter-associated genes associated with personality variation in humans (e.g. Drd4 dopamine receptor gene).
•Do Drd4gene variants associate with great tit personality in the selection lines?
Significant association between the Drd4 genotype and great tit personality score. Fidler et al. 2007.
———————————————————————————–
Example 2: Stickleback fish personality – do neurotransmitters cause variation?
Pharmacological manipulation experiment
- Monoamine systems evolutionarily conserved.
- Manipulation using:
Fluoxetine (SSRI) -serotonin
Ropinirole –dopamine agonist
Behavioural measures:
•Day 0 (before), 6 days of treatment, 18 days of treatment
•Boldness/exploration-novel environment: latency to move, time in upper-mid zone.
•Aggression–mirror test: number of attacks.
•Sociability–mirror test: time spent close to mirror.
Dopamine-& serotonin-manipulated fish were bolder
Abbey-Lee et al. (2019).
———————————————————————————
Summary
•Variation between individual great tits in exploratory/novelty-seeking behaviour is attributable to genetic variation.
•Part of this variation is related to variation in the dopamine receptor gene Drd4.
•Pharmaceutical manipulation shows a causal link between serotonin and dopamine & bold personality in stickleback fish.
Developmental explanations for animal personality variation
Developmental plasticity - Same genotype can result in different phenotypes depending on early environmental experiences (inc. learning)
Example: Does early-life stress cause individual differences in risk-taking in starlings?
hand raised chicks in a lab and manipulated their birds early experience by independently varying to different stresses; limiting the amount of food they received, and increasing how much effort they had to put into begging to get their food.
lean group of chicks got fed 75% of the amount of food they gave to their plenty siblings who fed as much as they wanted to eat.
hard group of chicks they made beg for twice as long as their easy siblings.
after 15 days old, they raised all of the chicks together identically with adlibitum food.
Next they wanted to try to confirm the manipulations of early life experiences had altered the stress the birds had experienced. they did this by measuring a biomarker of cumulative stress through telomere shortening. telomere shortening are protective caps on the ends of chromosomes made up of repetitive DNA sequences, and they get shorter every time a cell divides, so they shorten with an organisms age. but exposure to stress makes them short and faster.
so they measured the change in telomere shortening length between the start of manipulation and when they were 56 days old after the manipulation, to confirm that early life treatments have impacted this biomarker of stress. they found that both food restriction and the begging effort treatments had independent effects on telomere shortening. lean hard birds group had the most shortened telomeres indicating they had experienced the greatest early life stress as they had intended.
Summary
Experiencing stress in early life caused reduced risk-taking during foraging in adulthood in starlings.
Functional explanations for animal personality variation
Personality paradox?
•Why no single ‘optimal’ personality?
•How is genetic variation in personality traits maintained?
Personality paradox:
Why no single ‘optimal personality’? (explanation of variation of personality)
1. Frequency-dependent selection –fitness advantage of an allele depends on how common it is in the population.
2. Fluctuating selection –variation in the environment over time or space means the fitness advantage of an allele varies too.
3. Fitness trade-offs –an allele benefits fitness in one context but carries fitness costs in a different context.
4. Life-history trade-offs –trade-offs between growth, survival and reproduction. Life history strategy (Also referred to as ‘Pace of Life’); The age-and stage-specific patterns & timing of events in an organism’s life, inc. juvenile development, age of sexual maturity, first reproduction, number of offspring, parental investment, lifespan.
Personality paradox:
Why no single ‘optimal personality’?
Genetic variation in personality could be maintained due to:
•Frequency-dependent selection
•Fluctuating selection
•Fitness trade-offs
•Life-history trade-offs
These explanations need not be mutually exclusive.
——————————————————————————–
Example 1: How does natural selection maintain variation in great tit personalities?
Dingemanse et al. (2004).
Personality measure: novel environment exploration
Proxy fitness measures:
- Survival in wild (mark-release-recapture)
- Offspring survival to breed
3 years: winter food varied (low, high, low)
- Different patterns of survival between years & sexes
- Mothers’ personality predicted offspring survival-to-breed, but pattern also varied between years.
Dingemanseet al. 2004. - Fitness trade-offs: costs vs. benefits of aggressiveness
- Fluctuating selection: fitness of ‘bold’ and ‘shy’ great tits changed form year to year in line with variation in food availability and hence competition
•Fast-exploring females can better compete for food in poor winters?
•Fast-exploring males can better compete for territories in spring after rich winter?
Example 2: How does natural selection maintain variation in superb fairy-wren personalities?
Personality:
Nestling behaviour -early separation test and handling stress test (measured stillness, breathing rate).
Junvenile/adult behaviour•Exploration: novel environment (latency to enter, unique perching areas)
•Activity: novel environment (total perching areas)
•Aggression: mirror test
Fitness proxy: Survival (mark-release-recapture)
More exploratory wrens had higher mortality.
Condition-dependent risk-taking, as predicted by current vs future reproduction life-history trade-off:
- Explored more with age.
- Birds becoming lighter explored more.
Hall et al. 2015.
——————————————————————————–
Summary:
Life-history trade-offs could explain personality variation in superb fairy-wrens.
Fluctuating selection and fitness trade-offs could explain variation in personality in great tits.
Variation in life-history strategy provides a plausible functional explanation for widespread variation in animal personality: Different future expectations for reproduction result in differences in risk-taking.
Could evolutionary ideas help explain variation in human personality too?
•Heritable individual differences in humans e.g. personality
•Personality related to reproductive success in humans
Evolutionary perspective: variation on personality dimensions represents alternative strategies for maximizing fitness, due to cost/benefit trade-offs
Extraversion – what trade-offs might apply?:
1) Fitness benefits - Mating success: More sexual partners & extra-pair copulations. Social allies: Initiate more social behaviour, have more social support. Exploration.
2) Fitness costs - Social risks: More criminal/antisocial behaviour. Family instability: Higher chance of step-parenting for offspring. Physical risks: More accidents/illness.
Neuroticism –what trade-offs might apply?
1) Fitness benefits - Vigilance to avoid danger?Competitiveness - striving?
2) Fitness costs - Psychiatric disorders (e.g. depression and anxiety). Poorer health (stress). Relationship failure & social isolation
Evolutionary approach gives testable predictions:
E (Personality dimension) - (Prediction) More sexual partners but more injuries
N (Personality dimension) - (Prediction) Improved performance on perceptual monitoring e.g. detecting predator
O (Personality dimension) - (Prediction) Socially successful via creative activity OR socially marginalized via bizarre beliefs
C (Personality dimension) - (Prediction) Poor performance on tasks requiring responding spontaneously to changes in the local environment
A (Personality dimension) - (Prediction) Avoid being victims of interpersonal conflict but often get treated as ‘suckers’ (e.g. in public goods game or iterated prisoner’s dilemma game)
