Evolutionary Perspectives
on Personality
Origin Theories

Three theories of the origins of complex
adaptive mechanisms
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1. Creationism
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2. Seeding theory
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3. Evolution by natural selection
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Evolution and Natural Selection


All humans today come from an unbroken line
of ancestors who accomplished two tasks: They
survived to reproductive age, and they
reproduced
We carry adaptive mechanisms that led to our
ancestors’ success
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Natural Selection


Changes or variants that better enabled an
organism to survive and reproduce lead to more
descendants
Descendants inherit variants that led to their
ancestors’ success
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Natural Selection


Thus, successful variants are selected and
unsuccessful variants are weeded out
Over time, successful variants come to
characterize entire species
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Sexual Selection


Darwin noticed that many mechanisms seemed
to threaten survival, such as the peacock’s
elaborate plumage and the stag’s large antlers
Darwin proposed evolution by sexual selection
as solution—these traits evolved because they
contributed to an individual’s mating success
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Sexual Selection
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Sexual Selection

Two forms of sexual selection
 Intrasexual competition: Members of the
same sex compete with each other for sexual
access to members of the other sex
 Intersexual competition: Members of one sex
choose a mate based on their preferences for
particular qualities in that mate
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Genes and Inclusive Fitness

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Differential gene reproduction—reproductive
success relative to others
Calculate genetic gains and losses
Inclusive fitness theory (Hamilton, 1964)

Inclusive fitness: personal reproductive success
(number of offspring you produce) plus effects
you have on the reproduction of your genetic
relatives, weighted by genetic relatedness
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Products of the Evolutionary Process
Adaptations
 Byproducts of Adaptations
 Noise or Random Variation

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Adaptations

Adaptations are the primary products of
selection, defined as “reliably developing
structure in the organism which, because it
meshes with the recurrent structure of the
world, causes the solution to an adaptive
problem”
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Adaptations


Adaptive problem: Anything that impedes
survival or reproduction
Hallmark of adaptations are special design,
including efficiency, precision, and reliability.
E.g., food preferences, fear of snakes
 E.g. Jealousy, helping, defense mechanisms

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Byproducts of Adaptations

Byproducts are incidental effects of
adaptations not properly considered to be
adaptations
 e.g.,
nose
 e.g., language?
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Noise or Random Variation

Neutral with respect to selection
 e.g.,
shape of the human earlobe
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Evolutionary Psychology

Premises of Evolutionary Psychology
 Domain-specificity:
Adaptations are designed
by evolutionary process to solve specialized
adaptive problems
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Evolutionary Psychology

Premises of Evolutionary Psychology
 Numerousness:
Expectation is that there are
many psychological adaptations, because
different adaptations are required to solve
different adaptive problems
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Evolutionary Psychology

Premises of Evolutionary Psychology
 Functionality:
Psychological adaptations are
designed to accomplish particular adaptive
goals
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Proximate and Ultimate Causation

Proximate causation: Immediate causal forces—
development, input, mechanism


E.g., defense mechanisms used to avoid anxiety
Ultimate causation: Why? [example: Why are
men taller than women, on average?]

E.g., why do defense mechanisms exist?
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Core Tenets of Evolutionary
Psychology
Evolved psychological mechanisms are
instantiated in the brain.
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Human Nature


Human nature is a product of evolutionary
process
Psychological mechanisms that are successful in
helping humans survive and reproduce outreplicate those that are less successful
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Human Nature
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Over evolutionary time, successful mechanisms
spread through population and come to
characterize all humans
Examples of evolutionary analysis at the level of
human nature
The Need to Belong
 Helping and Altruism
 Defense Mechanisms
 Universal Emotions

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Human Nature
The Need To Belong
The most basic human motivators are status
and acceptance
 Social Anxiety – species typical adaptation
to prevent social exclusion
 Being part of a group has survival value

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Human Nature
Helping and Altruism
Helping others is a direct
function of the recipient’s ability
to enhance the inclusive fitness
of the helper
 The tendency to help is a direct
function of genetic relatedness

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Human Nature
Helping and Altruism

Who do you save from a burning
building?
 Son
vs. nephew?
 Son vs. daughter?
 Spouse vs. child?
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Human Nature
Defense Mechanisms
Ability to deceive self (DM)
increases ability to deceive others
 Deceiving others increases
likelihood of survival and mating
success

 E.g.,
threats, boss
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Sex Differences


Evolutionary psychologists expect that males
and females will be the same or similar in all
domains where sexes have faced the same or
similar adaptive problems
Expect sex differences in those domains where
sexes recurrently faced different adaptive
problems
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Sex Differences

Examples of differences between men and
women that are attributable to recurrently facing
different adaptive problems
Sex Differences in Aggression
 Sex Differences in Jealousy
 Sex Differences in Desire for Sexual Variety
 Sex Differences in Mate Preferences

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Sex Differences
Jealousy

Adaptive problem for men is paternity.
 Men
over evolutionary history have risked
investing in children who were not their own

Adaptive problem for women is child-rearing
resources.
 Women
over evolutionary history have risked
raising children without adequate resources
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Sex Differences
Jealousy
Males and females have evolved different
jealousy cues
 Men should be more jealous in response to
cues to a sexual infidelity
 Women become more distressed over a
partner’s emotional infidelity

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Sex Differences
Basic Method
1.
2.
Think of a serious, committed romantic relationship that you
have had in the past, that you currently have, or that you would
like to have. Imagine that you discover that the person with
whom you’ve been seriously involved has become more
interested in someone else. Of the following, which would
distress or upset you more?
Imagining your partner forming a deep emotional attachment
to that person.
Imagining your partner enjoying passionate sexual intercourse
with that person.
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Sex Differences
Jealousy
Findings
Universal
Problems
Forced choice only
Double shot
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Sex Differences
Mate Preferences

Evolutionary psychology predicts:
 Men value women’s physical appearance
which provides cues to her fertility
 Women value men’s financial resources
which help in raising the family
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Individual Differences
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
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Most challenging and difficult level of analysis
for evolutionary psychologists
Big Five personality traits as clusters of key
features of “adaptive landscape” of other people
Human have evolved “difference-detecting
mechanisms” designed to notice and remember
individual differences that have most relevance
for solving social adaptive problems
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Limitations of Evolutionary
Psychology

Adaptations are forged over long expanse of
evolutionary time, and we cannot go back to
determine with certainty what the precise selective
forces on humans have been
Forced to make inferences
 But current mechanisms provide windows for
viewing the past
 Learning more about our evolved mechanisms is a
tool for overcoming limitation of sparse knowledge
of ancestral environments

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Limitations of Evolutionary
Psychology


Evolutionary scientists have just scratched the
surface of understanding the nature, details, and
design features of evolved psychological
mechanisms
Modern conditions are undoubtedly different
from ancestral conditions in many ways, and so
what was adaptive in the past might not be
adaptive today
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Limitations of Evolutionary
Psychology

It is sometimes easy to come up with different
and competing evolutionary hypotheses for the
same phenomena—true of all science
Onus is on the researcher to fashion specific,
testable, and falsifiable hypotheses
 Thus, competing theories can be pitted against
each other and data can be the final arbiter

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Summary and Evaluation
(continued)

Evolutionary psychology has several limitations,
but this perspective adds a useful set of
theoretical tools to the analysis of personality at
levels of human nature, sex differences, and
individual differences
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Evolutionary Perspectives on Personality