Personality Psychology: Traits, Measurement, and Biological Bases

Personality

Personality is the set of psychological traits and mechanisms within the individual that are organized and relatively enduring, and that influence interactions with, and adaptations to, the environment.

LOTS

L = Life data (records, history), O = Observer data (ratings by others), T = Test data (standardized tests), S = Self-report data (questionnaires, interviews).

Theory in Personality Psychology

A theory must explain, predict, and be testable; it should organize known findings and guide future research.

Levels of Personality Analysis

Human nature (universal), group differences (age, culture, gender), and individual uniqueness (traits that make a person distinct).

Major Research Designs in Personality Science

Experimental, correlational, and case study designs.

Reliability

Reliability includes test-retest, internal consistency, and inter-rater.

Validity

Validity refers to the accuracy of a measure.

Response Sets

Response Sets include acquiescence, extreme responding, and social desirability.

Triangulation

Triangulation is the use of multiple methods or data sources to enhance the credibility of research findings.

Generalizability

Generalizability refers to the extent to which findings can be applied to settings beyond the study.

Correlation

Correlation is a statistical measure that describes the extent to which two variables are related.

Longitudinal Analysis

Longitudinal analysis involves studying the same subjects over a period of time to observe changes.

Case Study

A case study is an in-depth examination of a single individual or group.

Personality Trait Research Goals

To identify, describe, and measure traits; explain their origins; and predict behavior.

Internal Causal Properties vs Descriptive Summaries

Internal causal properties = traits drive behavior from within; Descriptive summaries = traits are simply categories of observed behavior.

Determining Important Traits

Different ways and approaches include lexical approach (language), statistical approach (factor analysis), and theoretical approach (theory-driven).

Organizing Traits

Models like the Five-Factor Model (Big Five), HEXACO, PEN model, Interpersonal Circumplex.

Personality and Environment Interaction

Through selection (choosing environments), evocation (eliciting reactions), and manipulation (intentionally influencing others).

Personality Change

Personality change can be systematic and enduring, often occurring in adolescence and young adulthood, though change can occur across the lifespan.

Rank-order stability

The consistency of an individual's relative standing on a trait compared to others over time.

Mean-level changes

Changes in the average level of a trait within a population over time, such as conscientiousness increasing with age.

Personality coherence

The same underlying trait expressed in different behaviors across life stages.

Cardinal traits

Traits that dominate an individual's personality and influence their behavior across various situations.

Lexical hypothesis

The idea that the most important personality traits will be encoded in language.

Act nomination

The process of identifying specific behaviors that exemplify a particular trait.

Continuum

A range or spectrum of traits rather than discrete categories.

Factor analysis

A statistical method used to identify underlying relationships between variables, often used in personality research.

Taxonomy

A classification system for organizing personality traits.

Big Five

A model of personality that includes five broad dimensions: extraversion, agreeableness, conscientiousness, neuroticism, and openness to experience.

NEO-PI-R

A personality inventory that measures the Big Five traits.

HEXACO

A model of personality that includes six dimensions: honesty-humility, emotionality, extraversion, agreeableness, conscientiousness, and openness to experience.

PEN

A personality model that includes three dimensions: psychoticism, extraversion, and neuroticism.

Honesty-humility

A personality trait characterized by sincerity, fairness, and modesty.

Agency

The capacity of individuals to act independently and make their own choices.

Communion

A personality trait focused on social relationships and connectedness with others.

Psychopathy

A personality disorder characterized by persistent antisocial behavior, impaired empathy, and remorse.

Narcissism

A personality trait characterized by grandiosity, a need for admiration, and a lack of empathy.

Machiavellianism

A personality trait characterized by manipulation and exploitation of others, often in a deceitful manner.

Heritability

The proportion of variation in a trait that can be attributed to genetic factors.

Shared environmental influences

Experiences that siblings have in common that affect their personality.

Nonshared environmental influences

Unique experiences that individuals have that contribute to differences in personality.

Epigenetics

The study of how environmental factors can influence gene expression and affect personality.

Twin studies

Research comparing monozygotic (identical) and dizygotic (fraternal) twins to understand genetic and environmental influences on personality.

Adoption studies

Research that examines the similarities between adopted individuals and their biological versus adoptive families to assess genetic and environmental influences.

Family studies

Research that investigates the resemblance of traits among family members to understand genetic influences.

Neurotransmitters

Chemical messengers in the brain that influence personality and behavior, including dopamine, serotonin, and norepinephrine.

Physiological measures

Methods used in personality research to assess biological responses, including EEG, fMRI, heart rate, skin conductance, and hormone assays.

Brain asymmetry

The concept that the two hemispheres of the brain may have different functions, though both work together.

Triangulation

Using multiple data sources or methods to cross-check findings.

Generalizability

Extent to which results apply across people, settings, and time.

Correlation

A statistical relationship between two variables (positive or negative).

Longitudinal Analysis

Research that measures the same variables in the same people across time.

Case Study

An in-depth examination of a single individual.

Trait

A consistent pattern of thoughts, feelings, or behaviors.

Cardinal Trait

A dominant trait that defines a person's life.

Lexical Hypothesis

Important traits will be encoded in language.

Act Nomination

Identifying behaviors that exemplify traits.

Continuum

Traits vary in degree, not kind (from low to high).

Factor Analysis

A statistical method for grouping related traits.

Taxonomy

A system for classifying traits.

Extraversion

Sociability, activity, assertiveness.

Agreeableness

Kindness, trust, cooperativeness.

Conscientiousness

Organization, responsibility, dependability.

Neuroticism

Emotional instability, anxiety, moodiness.

Openness to Experience

Curiosity, imagination, creativity.

NEO-PI-R

A personality inventory measuring the Big Five.

HEXACO Model

Personality model with six traits (adds Honesty-Humility).

PEN Model

Eysenck's 3-factor model (Psychoticism, Extraversion, Neuroticism).

Honesty-Humility

Sincerity, fairness, modesty.

Agency

Orientation toward self-assertion and achievement.

Communion

Orientation toward others and relationships.

Psychopathy

Callousness, impulsivity, antisocial traits.

Narcissism

Grandiosity, entitlement, self-focus.

Machiavellianism

Manipulativeness, exploitation, cynicism.

Rank-Order Stability

Maintenance of trait position relative to others over time.

Mean Stability

Average levels of a trait remain similar across time.

Coherence

Different behaviors expressing the same underlying trait across time.

Situationalism

Behavior varies depending on context.

Aggregation

Combining multiple observations to improve reliability.

Flux

Short-term variability in traits.

Selection

Choosing environments based on personality.

Evocation

Personality elicits certain reactions from others.

Manipulation

Intentionally influencing others' behavior.

Temperament

Early-appearing, biologically based tendencies in reactivity and regulation.

Genome

The complete set of genetic material in an organism.

Eugenics

The idea of improving the human race through selective breeding (discredited/controversial).

Heritability

The proportion of variance in traits explained by genetic differences.

Monozygotic Twins

Identical twins from a single fertilized egg.

Dizygotic Twins

Fraternal twins from two separate fertilized eggs.

Epigenetics

Environmental factors altering gene expression without changing DNA sequence.

Plasticity

The brain's ability to change through experience.

Neurotransmitters

Chemicals transmitting signals across neurons (e.g., dopamine, serotonin).

Monoamine Oxidase (MAO)

Enzyme regulating neurotransmitters, linked to personality and behavior.

Dopamine

Neurotransmitter linked to reward, motivation, and novelty seeking.

Serotonin

Neurotransmitter linked to mood regulation and emotional stability.

Norepinephrine

Neurotransmitter linked to arousal, vigilance, stress response.

Cardiac Reactivity

Heart rate and blood pressure response to stress.

Adaptation

Traits evolved to increase survival/reproduction.

Reactive Heritability

Traits influenced by heritable physical characteristics (e.g., strength influencing aggressiveness).

Frequency-Dependent Selection

Traits' value depends on how common they are in a population.