Comprehensive University Study Notes: Evolutionary Perspective, Behavioral Genetics, and Personality Psychology

Evolutionary Perspective and Psychological Mechanisms

• Nonhuman Personalities: Closely related species often exhibit similar personality traits, suggesting a concept of Evolutionary Continuity. This principle posits that all animal capacities and behaviors exist in continuity with other species, challenging the concept of Human Exceptionalism, which is not widely supported by current research.
• Evolution and Natural Selection: Processes involving survival and reproduction create adaptations over time.     * Hostile Forces of Nature: These include food shortages, diseases, parasites, and predators.     * Variants: Specific genetic variations that helped organisms survive these forces increased the likelihood of reproduction.
• Sexual Selection: The evolution of characteristics based on mating benefits rather than survival.     * Intrasexual Selection: Competition between members of the same sex (e.g., two males fighting for access to females).     * Intersexual Selection: Choosing a mate based on specific preferences for certain qualities.
• Inclusive Fitness: This refers to the products of the evolutionary process.     * Adaptations: The primary product of the selective process designed to solve Adaptive Problems (anything impeding survival or reproduction).     * Byproducts of Adaptations: Incidental effects not considered formal adaptations themselves.     * Evolutionary Noise: Random variations that are neutral to selection.
• Evolutionary Psychology Foundations:     * Modern humans carry adaptive mechanisms that led to the success of our ancestors.     * Human nature and personality are collections of evolved traits and mechanisms.     * Communion vs. Agency: Getting along (Communion) is considered more important evolutionarily than getting ahead (Agency).     * Domain Specificity: Adaptations are designed to solve particular problems. Different adaptive problems require different solutions. A higher number of problems leads to a higher number of adaptive mechanisms.
• Psychological Adaptations:     * Fear and Phobias: Evolved to combat hostile forces.     * Selection of Mates: Goal-oriented selection for reproductive success.     * Detection of Cheaters: A mechanism designed to prevent exploitation in social exchanges.
• Functionality: Psychological mechanisms are specifically designed to accomplish particular adaptive goals.
• Research Methods in Evolutionary Psychology:     * Deductive Reasoning Approach: A "top-down" or theory-driven method.     * Inductive Reasoning Approach: A "bottom-up" or data-driven method.

Human Nature: Social and Altruistic Behaviors

• The Need to Belong: One of the most basic human motivators, driven by needs for status and acceptance.     * Social Anxiety: Evolved because being excluded was life-threatening throughout human history. Distress regarding negative evaluation by others helps prevent social exclusion.     * External Threats and Cohesion: External threats increase group cohesion. Intense threats result in stronger social bonding to acquire and protect resources.
• Self-Esteem as a Monitor: Self-esteem monitors social inclusion. Those who spend more time with others generally report higher self-esteem. Failure to satisfy the need to belong results in Social Pain, which correlates with poor physical health, including high blood pressure, high perceived stress, and high cortisol levels.
• Evolutionary Benefits of Empathy and Social Cohesion:     * Bonobos: A subspecies of chimpanzees that are highly affectionate and solve conflicts through sexual interaction and empathy.     * Rhesus Monkeys: Demonstrated altruism by refusing to pull a chain for food if it resulted in a shock to a companion.
• Helping and Altruism: Helping others is linked to the recipient's ability to enhance the inclusive fitness of the helper.     * Kin Selection: Individuals are significantly more likely to help highly related kin in life-or-death situations to ensure the passing of shared genes.     * Magnitude of Help: In significant (costly) help scenarios, the young are prioritized. In insignificant help scenarios, both the very young and the very old receive help.     * Interspecies Altruism: Examples include humpback whales saving other species from killer whale attacks, though no direct benefit for the humpback whale has been identified.
• Universal Emotions: From an evolutionary perspective, emotions are universal and recognized similarly across cultures.     * Study Data: A study using facial pictures across many countries showed agreement on $7$ universal emotions.     * Fore of New Guinea: A group with no contact with outsiders correctly paired emotions with facial expressions, supporting universality.

Aggression, Sex Differences, and Individual Variation

• Aggression and Warfare: Narcissism (pursuit of status) and organized warfare are observed primarily in chimpanzees and humans.     * ADRA2C Gene: Low expression of this gene makes individuals more likely to engage in fight-or-flight responses, leading to fights over resources.
• Evolutionary Predicted Sex Differences: Sexes differ significantly in domains where they faced different adaptive problems.     * Theory of Parental Investment: Females can only bear a small number of offspring and are thus more careful in mate choice. Males must compete for access.     * Effective Polygyny: Variance in reproduction between sexes leads to competition within the sex showing high variance.
• Jealousy Strategies:     * Male Perspective: Males face paternity uncertainty. A partner's pregnancy by another male jeopardizes the certainty of passing on genes. Males are more jealous regarding Sexual Infidelity.     * Female Perspective: Females are certain of their maternity but risk losing paternal investment. Females are more jealous regarding Emotional Infidelity.     * Attachment-Fertility Study: Harris found that while both sexes are distressed by sexual infidelity, they may experience jealousy similarly regarding emotional concerns.
• Mate Preferences:     * Females: Place higher value on a potential mate's financial resources.     * Males: Place higher value on a female's physical appearance.     * Shared Values: Both sexes value kindness, understanding, and an exciting personality.
• Individual Differences and Environmental Triggers:     * Evocation: Specific conditions (e.g., cues of infidelity) evoke different psychological reactions, such as jealousy or neuroticism depending on early life stress.     * Childhood Adversity: Correlates with lower agreeableness, high anger, and aggression. An Australian study found adversity increases risk for negative affect but only correlates with antisocial tendencies in children with low MAOA levels.
• Father Presence vs. Absence (Ages $1-5$):     * Father-Absent: Children develop expectations that resources are unreliable and relationships are not enduring. Characterized by early sexual maturation, frequent partner switching, and impulsivity.     * Father-Present: Children develop expectations that people are trustworthy and relationships endure. Characterized by delayed sexual maturation and heavy investment in long-term relationships.
• Contingencies Among Traits: Traits like being big and strong make a quick temper more "adaptive" or advantageous. Extraversion is more advantageous for those who are strong and physically attractive.
• Frequency-Dependent Selection: The success of a trait (e.g., cheating or psychopathy) depends on its frequency. If these traits become too common, others learn to detect them, and the competitive advantage is lost. Psychopathy is maintained at a low frequency to remain an adaptive advantage.
• Balancing Selection: No single value of a Big Five trait is unconditionally optimal.     * Neuroticism: Benefit of vigilance to danger vs. cost of stress reactivity.     * Extraversion: Benefit of mating success vs. cost of risk and family instability.     * 7R Allele (DRD4): Higher rates in North America (migration/novelty-seeking) vs. lower rates in Asia. This allele is associated with exploratory behavior and potentially ADHD as an adaptive advantage in nomadic populations.

Behavioral Genetics

• Genome and Genetic Junk: The genome is the complete set of genes. "Genetic junk" was once thought functionless but may impact traits.
• Eugenics: The controversial notion of designing the future of the human species by reproducing only certain traits.
• Heritability ($h^2$): Specifically refers to the proportion of phenotypic variance (observed individual differences) attributable to genotypic variance (total genetic differences).     * Formula: If heritability is $.50$, then environmentality is $.50$.     * Nature-Nurture Debate: At the population level, psychologists ask what percentage of variance is due to genes vs. environment. At the individual level, the answer is always both.     * $10,000$-Hour Rule: Despite practice, genes still account for over $50\%$ of variance in elite ability.
• Methods of Research:     * Selective Breeding: Not performed on humans but provides evidence in animals.     * Family Studies: Examine genetic relatedness and personality similarity.     * Twin Studies: Compares Monozygotic (MZ, $100\%$ genes) vs. Dizygotic (DZ, $50\%$ genes) twins.         * Equal Environments Assumption: Assumes MZ and DZ twins experience similar family environments.         * Representativeness Assumption: Assumes twin findings apply to the general population.     * Adoption Studies: Examine correlations between adopted children and biological parents (genetic) vs. adoptive parents (environmental).
• Heritability Findings:     * Extraversion: Approximately $40\%$.     * Neuroticism: Approximately $30\%$.     * Traditionalism: Strongly heritable.     * Aggressiveness: $51-72\%$.     * Psychopathic Traits: Moderate to high heritability in humans and chimpanzees.     * Sexual Orientation: $30-70\%$ heritability ($32\%$ in some specialized twin studies). Concordance for male identical twins is $20\%$ and for female identical twins is $24\%$. Childhood gender nonconformity shows heritability of $50\%$ in men and $37\%$ in women.     * Drinking and Smoking: Moderate heritability for drinking ($.36$ to $.56$). Alcoholism heritability is $.50$ or higher.
• Environmental Influences:     * Shared Environment: Parents' beliefs, number of TVs. Has little influence on personality but affects attitudes, religious beliefs, and health behaviors.     * Nonshared Environment: Unique experiences (birth order, peer influence). These account for the majority of environmental influence on personality.
• Molecular Genetics:     * DRD4 Gene: Associated with novelty seeking. The 7R+ variant is linked to higher financial risk-taking.     * 5-HTTLPR: Serotonin transporter gene linked to neuroticism and depression.     * GWAS: Genome-wide association studies look at the sum of many genetic variants.
• G-E Interaction and Correlation:     * Interaction: Different responses to the same environment (e.g., introverts vs. extroverts in a noisy room).     * MAOA Interaction: Abused children with low MAOA are much more likely to become violent adults.     * Passive Correlation: Parents provide both genes and the environment (e.g., highly verbal parents having many books).     * Reactive Correlation: Parental response depends on the child's genotype (e.g., hugging "cuddler" babies more).     * Active Correlation: Individuals seek out environments that fit their genotypes (e.g., sensation seekers choosing skydiving).
• Epigenetics: How environment determines gene expression. Mice exposed to stress passed stress reactivity to offspring through epigenetic changes, even without contact.

Personality Stability, Coherence, and Change

• Three Types of Stability:     * Rank Order Stability: Maintaining one's position within a group over time. High test-retest correlations suggest stability.     * Mean Level Stability: Average level of a trait in a group remains constant over time. If the average changes, it is "Normative" change.     * Personality Coherence: Maintaining rank order but changing the outward manifestation of the trait (e.g., a dominant child bossing peers vs. a dominant adult leading a meeting).
• Life Outcomes and Personality:     * Marital Dissatisfaction/Divorce: Predicted by high neuroticism (both spouses) and lack of impulse control (husband).     * Health and Longevity: Predicted by high conscientiousness, high extraversion, low hostility, and low neuroticism.     * Academic/Work Achievement: Predicted primarily by high conscientiousness.
• Normative Changes Over Time:     * Sensation Seeking: Increases in childhood, peaks at $16-20$, then decreases.     * Self-Esteem: Declines during adolescence (more significantly for girls), then increases through adulthood.     * The Big Five: Conscientiousness, Agreeableness, and Emotional Stability generally increase with age (Psychological Maturation), while Openness and Extraversion tend to decline.
• Stability Thresholds: Personality becomes more stable as people age, peaking in the $50s$. However, extreme changes can occur due to physical trauma, such as Phineas Gage (frontal lobe injury) becoming more impulsive.
• Analysis Levels: Population level (everyone), Group differences (sex/culture), and Individual differences.
• Temperament in Infancy: Rothbarth identified $6$ factors. Activity level and smiling show higher stability than other variables. Stability increases as infants mature and is higher over shorter intervals.
• Longitudinal Measurement:     * Actometers: Recording devices for physical activity.     * Stability Coefficient: Correlation between same measures at different times.     * Validity Coefficient: Correlation between different measures of the same trait at the same time.

Traits, Taxonomies, and Assessment

• Formulations of Traits:     * Internal Causal Properties: Traits like neuroticism cause behavior.     * Descriptive Summaries: Traits are simply categories of acts (Act Frequency Approach involving act nomination and prototypicality judgments).
• Taxonomy Identification Approaches:     * Lexical Approach: Uses language. Criteria include Synonym Frequency and Cross-cultural Universality.     * Statistical Approach: Uses factor analysis and factor loadings to group items.     * Theoretical Approach: Based on specific theories (e.g., Maslow).
• Major Taxonomies:     * Eysenck’s Hierarchical Model: Psychoticism (P), Extraversion (E), and Neuroticism (N). Based on biological underpinnings like CNS arousal and testosterone levels.     * Wiggins’ Interpersonal Circumplex: Focused on Agency (Status) and Communion (Love). Relationships defined by Adjacency (positive correlation), Bipolarity (opposite), and Orthogonality ($90$ degree/unrelated).     * Five-Factor Model (Big Five): Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism (OCEAN). Measured via NEO-PI-R.     * HEXACO Model: Adds the factor of Honesty-Humility (H). High H correlates with sincere apologies; low H correlates with sabotage and the Dark Triad.
• Dark Traits:     * Dark Triad: Machiavellianism (manipulative), Narcissism (entitlement), and Psychopathy (low empathy).     * Dark Tetrad: Adds Dispositional Sadism (enjoyment from hurting others, internet trolling).
• Person-Situation Interaction:     * Situationism: Behavior is determined by situational factors (Zimbardo).     * Interactionism: Behavior is a function of both personality and the situation ($Behavior = f(P \times S)$).     * Aggregation: Averaging observations provides a better measure than single acts.     * Strong Situations: Situations where everyone acts the same (e.g., public speaking, grief).     * Weak Situations: Ambiguous situations where personality has the strongest influence.
• Data Measurement (LOTS):     * S-Data: Self-report (surveys).     * O-Data: Observer-report (inter-rater reliability).     * T-Data: Test data (IQ, fMRI, actometers).     * L-Data: Life-outcome data (marriage, speeding tickets).
• Evaluation Standards: Reliability (repeated measurement), Validity (Predictive, Convergent, Discriminant, Construct), and Generalizability (avoiding WEIRD bias).
• MBTI (Myers-Briggs Type Indicator): Widely used but limited by low test-retest reliability, use of median cutoff scores, and a typology scheme that ignores within-category differences. It assumes categories while most traits are normally distributed dimensions.
• Personnel Selection: Tests used to predict integrity and prevent negligent hiring (e.g., MMPI II, 16 PF). Consideration of Disparate Impact and rights to privacy is essential.