Differential Psychology Overview

Differential Psychology

• Differential psychology focuses on between-person differences, identifying stable patterns to compare individuals.
• Two key disciplines in scientific psychology are experiments (manipulating conditions) and correlations (measuring existing patterns).
• Both approaches can potentially overlook the influence of the other on their findings.

Kinds of Differences

• Demographic status: includes age, sex, marital status, religious affiliation, and political views.
• Lifestyle factors: encompass diet, exercise, and alcohol consumption.
• Experiences and upbringing: such as wealth and educational opportunities.
• Psychological attributes: encompassing motivation, goals, risk tolerance, gender identity, and sexuality.

Psychological Attributes

• Individual differences create "noise" or error in psychological experiments.
• This error is often domain-specific, not universal.
• Statistically, these differences are referred to as variance.

Traits

• Traits are characteristics that predict behaviors.
• Psychological traits are hypothesized to reside within individuals, distinguish among them, and remain relatively stable over time.

Intelligence

• Intelligence is the capacity to understand and acquire knowledge.

Personality

• Personality comprises the unique characteristics that define an individual.

Variation Differences

• Variations in personality and intelligence are related to life outcomes.
• These relationships are not predetermined; traits are not destinies.

Difficulties in Measurement

• Direct observation of psychological constructs is often impossible.
• Defining traits consistently and achieving consensus is challenging.

Personality and Intelligence

• Hierarchical models of personality and intellectual abilities exist.
• They show how different types of intelligence exist (e.g., verbal, emotional).
• Fluid intelligence refers to fixed cognitive capacities (tested with figural tasks).
• Crystallized intelligence involves acquired knowledge and procedures (tested by verbal tasks).

Personality

• Personality is an individual's characteristic patterns of thinking, feeling, and behaving.
• Defining personality comprehensively is complex due to the varying elements and lack of consensus.

Similarity and Differences

• Personality and intelligence traits are heritable and develop, but remain stable.
• Individuals actively shape their personality and development, although constrained by the environment.
• Typical performance is behavior without pressure; maximal performance is behavior under extreme pressure.

How Tests are Used

• Research: tests are used for description, prediction, and explanation.
• Practice: tests assist in selection, diagnosis, and classification.

Trait Development

• Development is a change process, either emerging or diminishing traits over time.

Genetics

• Genetic predispositions from both parents contribute to offspring traits.
• Dominant: traits expressed if inherited from at least one parent.
• Recessive: traits expressed only if inherited from both parents.
• Polygenic: multiple genes influencing a single trait.
• Pleiotropic: one gene influencing multiple traits.

History and Measurement

• Despite background commonalities, individuals differ in psychological characteristics.
• Early personality psychologists used the lexical hypothesis and identified personality traits through language.

Eugenics

• Eugenics aimed to improve humans through selective breeding.
• Negative eugenics: discouraging reproduction in individuals with undesirable traits.
• Positive eugenics: encouraging reproduction in individuals with superior traits.
• These approaches are based on flawed understandings of genetics.

Psychological Constructs

• Psychological constructs are latent variables, not directly observable.
• Observable behavior patterns help researchers infer the variables.

Basic Measurement

• Measurement involves using scalar units and a fixed "ground truth".
• Standard metrics, like centimeters for height, exhibit consistent and continuous scales.
• Measurement methods and consistency matter.

Error in Measurement

• Measurement error is the divergence from the true score.
• Sources of bias can lead to inaccurate test results.

Inferences about Results

• Measurement interpretations vary. For example, 160 cm might be considered short for a man, typical for a woman.
• Reliability assesses measurement consistency; validity ensures accurate measurement.
• Correlation measures the association between variables.

Personality Measurement

• A priori: creating subtests based on initial assumptions.
• A posteriori: identifying associations using factor analysis (the correlations within the test).

Personality Traits

• A person's consistent adapting to environmental demands.

Personality "Type" Models

• Organizing individuals into discrete categories.
• Personality traits influence behaviors less straightforwardly than initially thought.
• An interactionist perspective acknowledges that traits and environments interact to shape behavior.

Big Five/Five-Factor Model

• This model encompasses openness to experience, conscientiousness, extraversion, agreeableness, and emotional stability/neuroticism.
• Important related factors include antisocial behavior, social dominance, morality, and spiritual tendencies.
• This framework's effectiveness is attributed to personality's influence on behavior and life choices.

ABCD’s

• Affect: Feelings
• Behavior: Actions
• Cognition: Thoughts
• Desire: Wants

Measuring Personality

• Personality inventories: self or other reports assessing statement applicability.
• Projective techniques: responding to ambiguous stimuli; responses are interpreted by the administrator.
• Empirically designed objective tests: identifying items distinguishing subgroups.
• Limitations: faking, lack of self-insight, ambiguity; benefits: comprehensive data, practicality, and motivation.

Self-Presentation Bias

• Neutral, less biased items are used to reduce self-presentation biases in personality tests.

Intelligence Measurement

• IQ scores (typically following a normal distribution) represent scores on specific tests.
• Cognitive ability encompasses related but not always identical concepts including intelligence and working memory.
• Vocabulary, identifying progressions, and processing speed are typical cognitive tests.

Disadvantages of Intelligence Tests

• Artificial context, low real-world relevance, possible intimidation.

Flynn Effect

• Secular increases in average IQ scores.
• Early 20th century IQ measurements might appear as intellectual disabilities according to current standards.

Development of Differences

• Individuals show variation in developmental paths.
• Establishing change/stability in individual differences requires data and appropriate designs (longitudinal or cross-sectional).

Populations Representation

• Sampling entire populations is usually impractical.
• Larger samples are generally better (law of large numbers).

Kinds of Change

• Quantitative: Magnitude changes with same mechanisms (requires standard measurement).
• Qualitative: Capacity emergence or disappearance (no common measurement).

Measuring Change Over Time

• Mean-level change assesses average trait scores over time.
• Rank-order stability assesses relative differences over time.

Change in Intelligence

• Relatively stable throughout life, with declines in old age.
• Research challenges include dropout and confounding factors.

Change in Personality

• Personality is largely stable over the lifespan, but some changes occur.
• The "Maturation Principle" suggests increasing conscientiousness and agreeableness.

Genetics and Heritability

• All psychological characteristics are heritable (e.g., intelligence, personality, psychopathology, motivations/goals, interests, happiness).

Key Terms

• G = Genes
• E = Environment
• P = Phenotype
• h = Heritability
• e = Environmental effects
• r = Gene-environment correlations

Twin Studies

• Monozygotic (MZ) vs. dizygotic (DZ) twins provide a natural experiment to study genetic and environmental contributions to traits.
• Examining correlations in MZ and DZ twins provides insights into genetic influences.
• Assessing shared vs. non-shared environments is also possible.

What is Heritability?

• Proportion of population variance attributable to genetic influences.

What About the Rest?

• The remaining variance is due to shared or non-shared environmental factors.

Laws by Behavioral Genetics

• Turkheimer's laws:
  • All human traits are heritable.
  • Shared environments tend to be less influential than genes.
  • Neither genes nor shared environment account for all variance.
  • Many genes impact traits, but individually they each account for little.
• Environmental influences are idiosyncratic.
  • Transact with genes uniquely and unpredictably.

Finding Genes

• New technologies enable examining gene profiles and trait associations.

Influences of Environment

• There is often implicit belief in environmental influences.

Standard Social Science Model

• Identifying environmental causes and outcomes.
• This model has limitations in adequately accounting for other variables.

ACE Model

• Distinguishing genetic (A), shared environmental (C), and non-shared environmental (E) influences.

Non-Shared Environments

• Often studied through life events, which can broadly influence many traits,
• Universal effects don't necessarily lead to differences.

Educational Exposure – IQ

• Educational reforms and longer schooling are associated with higher average IQ.
• This relationship likely reflects cohort effects more than individual differences.

Taking an Active Role in Development

• Gene-environment correlations.

Personality Dynamics

• Short-term vs. long-term effects of traits and environments.

Five Factor Theory Representation

• Personality is composed of basic tendencies (biological, innate) and characteristic adaptations (learned, influenced by the environment).