David Buss: Evolutionary Theory of Personality

Charles Darwin's Contribution to Evolutionary Theory

Darwin’s major contribution was not the theory of evolution itself but an explanation for how evolution works, namely through selection (natural and sexual) and chance.

Artificial Selection

Occurs when humans select particular desirable traits in a breeding species;

for example, the Great Dane and Chihuahua were developed through human breeding preferences.

Natural Selection

A process where traits become more or less common over time based on their contribution to survivability, leading to “evolved strategies” for survival without conscious planning.

Sexual Selection

Occurs when traits are selected because they are attractive to the opposite sex and are reliable indicators of fitness, even if they do not aid survival (e.g., peacock plumage).

Adaptations

Evolved strategies with a genetic basis that solve survival or reproductive problems

examples include sweat glands, taste preferences, and human intelligence

By-products

Traits that result from adaptations but do not serve a direct function themselves,

like scientific ability or driving skill, which arise from intelligence and coordination.

Noise (Random Effects)

Random changes in design that do not affect function and are not selected for;

an example is whether a belly button is an “innie” or “outie.”

Example of a By-product

The ability to drive a car is a by-product of adaptations such as hand-eye coordination and muscle control, not an evolved strategy itself.

Evolutionary theory

This theory posits that personality traits originate from ancestral interactions between changing environments and changing bodies/brains.

It aims to explain the ultimate origins, function, and .

grand theories

Personality theories evolved from __ theories explaining all human behavior to more focused ones addressing specific aspects like structure or self, often biological influences.

Evolutionary Meta-Theory (Buss)

Buss argues that evolutionary theory offers a comprehensive framework for personality psychology, which has been largely absent in earlier formulations.

Common Ground Between Personality and Evolution

Both fields start with the assumption that individuals differ from one another, making them seemingly natural partners for integration.

Fundamental Situational Error

This error, or the that the environment alone can produce behavior void of a stable internal mechanism.

false

The nature vs. nurture divide is __ because internal processes depend on environmental input, and vice versa—

Fundamental Attribution Error

The tendency to overemphasize internal dispositions and ignore environmental influences when explaining others’ behaviors.

Evolved mechanisms

These mechanisms are examples of nature-nurture interaction, as they are biological traits that respond to environmental stimuli and

Evolution as a Nature-Nurture Process

Evolution is inherently about the interaction between biology and environment; traits that proved adaptive in certain environments were passed down.

• Survival

• Reproduction

According to Darwin, all life must solve 2 key problems to persist: _ and _

Hostile Forces of Nature

Environmental challenges like disease, predators, food shortages, harsh climates, and parasites that threaten survival

Mechanisms (in Evolution)

Evolved solutions to adaptive problems that operate in specific domains to address survival or reproductive challenges.

Characteristics of Mechanisms

• Domain-specific (solve one adaptive problem)

• Numerous (dozens to thousands)

• Complex solutions (convert inputs into decisions or behaviors)

Physical Mechanisms

Physiological organs or systems (e.g., sweat glands, immune system) that solve survival problems and are often shared among species.

Psychological Mechanisms

Internal and specific cognitive, motivational, and personality systems that solve specific survival and reproduction problems.

Role of Evolutionary Psychology

Focuses on the origin and function of psychological mechanisms, unlike evolutionary biology, which focuses on physical traits.

Categories of Psychological Mechanisms

1. Goals/Drives/Motives

2. Emotions

3. Personality Traits

Power and intimacy

_ and_ are evolved goals/motives that support survival and reproduction

Forms of the Power Motive

Aggression, dominance, achievement, status, negotiation of hierarchy.

Forms of the Intimacy Motive

Love, attachment, reciprocal alliance

Buss’s View of Personality Traits

For him, Personality traits are evolved mechanisms that signal an individual's ability to solve survival and reproduction problems; they are adaptive strategies with evaluative and social significance.

Evaluative Function of Traits

Personality traits allow others to assess individuals' fitness for cooperation, leadership, trustworthiness, and mating—thus conferring a reproductive advantage to accurate perceivers.

5 Major Personality Dimensions (David Buss)

1. Surgency/Extraversion/Dominance

2. Agreeableness/Hostility

3. Conscientiousness

4. Emotional Stability (vs. Neuroticism)

5. Openness/Intellect

Surgency/Extraversion

Trait involving dominance, sociability, risk-taking, leadership, and positive emotions; adaptive for negotiating hierarchy, gaining status, and attracting mates

Agreeableness

Trait involving cooperation, warmth, group harmony, and conflict resolution; adaptive for group cohesion and alliance formation.

Conscientiousness

Trait involving reliability, attention to detail, focus, and dependability; signals trustworthiness and task commitment, important for group survival and collaboration.

Emotional Stability (Low Neuroticism)

Trait involving emotional resilience, calmness under stress; moderate anxiety is adaptive, but too little or too much is maladaptive.

Openness/Intellect

Trait involving curiosity, problem-solving, creativity, and openness to new experiences; adaptive for innovation and environmental exploration.

Most Adaptively Important Traits (David Buss)

1. Surgency/dominance – Social hierarchy and leadership

2. Agreeableness – Group harmony and trust

3. Conscientiousness – Reliability and task success

Surgency

___ involves the disposition to experience positive emotional states and to engage in one’s environment and to be sociable self-confident

Biological-genetic (nature); Environmental-social (nurture)

Evolutionary theory incorporates both _____ and _____ sources to explain individual differences.

4 Sources of Individual Differences (Buss & Greiling)

1. Early Experiential Calibration

2. Attachment Style

3. Alternative Niche Specialization

4. Heritable/Genetic Differences

Early Experiential Calibration

Childhood experiences shape behavioral strategies.

Example: Father absence leads to promiscuous sexual strategies due to unreliable parental investment.

Attachment Style

Adaptive attachment between caregiver and infant ensures survival; attachment experiences in childhood influence adult relationship patterns (secure, avoidant, etc.).

Birth Order and Personality (Sulloway, 1996)

• Firstborns: Align with authority, responsible.

• Later-borns: Rebel, seek independence and uniqueness.

Alternative Niche Specialization

Individuals develop unique traits or behaviors to stand out and gain attention from parents or mates.

Example: Birth order effects influence personality (Sulloway, 1996)

Heritable/Genetic Sources of Differences

Traits influenced by genetics include body type, facial features, and physical attractiveness, which affect social and mating opportunities.

Physical Attractiveness and Heritability

Traits like muscularity or dominant facial features are heritable and increase reproductive success through increased sexual opportunities.

Nonadaptive Sources

Individual differences that do not affect survival or reproductive success.

Example: Neutral genetic variations or mutations that are neither harmful nor beneficial.

Neutral Genetic Variations

Genetic mutations that are nonadaptive, meaning they don’t influence fitness and can persist in the gene pool until affected by natural or sexual selection.

Maladaptive Sources

Traits or differences that harm survival or reduce sexual attractiveness. Can arise from genetic defects or environmental trauma.

Genetic Defect (Maladaptive Source)

A harmful genetic mutation that negatively impacts the individual’s health or reproductive fitness.

Environmental Trauma (Maladaptive Source)

External damage, such as brain or spinal cord injuries, that leads to maladaptive personality traits or behaviors

Neo-Bussian Evolutionary Theories

Extensions of David Buss’s evolutionary personality theory by theorists like MacDonald and Nettle, emphasizing personality as evolved, adaptive strategies for solving environmental challenges.

MacDonald's Four Personality Dimensions

Dominance, Conscientiousness, Nurturance, and Neuroticism

(excluded Openness from Big Five).

Inclusive Fitness (Explained Simply)

We help close relatives more than distant ones or strangers because we share more genes, even though we don’t consciously calculate this.

Temperament

Biologically based individual differences in behavior evident from birth, forming the foundation for later personality traits. Modified by environmental input.

Prenatal Stress Effects

Maternal stress during pregnancy can alter infant stress response—higher baseline stress hormones and stronger physiological stress reactions persisting into childhood.

4 Dimensions of Infant Temperament

• Activity (energy level)

• Emotionality (intensity/frequency of emotions)

• Sociability (response to strangers)

• Impulsivity (readiness to act without reflection).

Polygenic Traits

Personality traits are influenced by many genes, not just one.

Complex traits like anxiety or aggression are polygenically transmitted.