Psychology of Individual Differences Lecture 1

Introduction to Individual Differences

• Individual differences refer to the observable differences between individuals in terms of interests, values, preferences, physical, and psychological characteristics.
• Branch of psychological knowledge that focuses on understanding these differences.

Types of Differences

• Interindividual differences: variations between individuals in one or more traits, behaviors, or characteristics.
• Intraindividual differences: differences observed within the same person when assessed at different times or in different situations.

Key Terms

• Trait: enduring patterns of behavior and thought that are relatively consistent over time and across various situations.
• Factor: a psychological characteristic that distinguishes one person from another and helps define individuality.
• Dimension: a continuum from minimum to maximum intensity of a given feature.
• Disposition: a construct used to describe the stability of human behavior over time.
• Type: the dominant quality or qualities distinguishing a person or group.

Traits

• Internal psychological disposition that remains largely unchanged throughout the lifespan and determines differences between individuals.
• Descriptive traits: the sum of variables that describe the observable consistency of behavior that has occurred in the past.
• Latent traits: features that cannot be directly observed.

Trait vs State

• Traits: long-term conditions, revealed in response to a stimulus or in specific situations, abstract, and depend on the person.
• States: short-term conditions, manifest themselves continuously, specific, and depend on the situation.

Behavioral Genetics

• Study of the biological basis of individual differences.
• Phenotype: expression of an individual's genes in behavioral traits that can be measured.
• Heritability estimate: a statistical indicator of the influence of genetic factors on individual differences in behavioral traits.

Family Studies

• Comparing pairs of people with different degrees of relatedness (e.g., MZ and DZ twins reared together and MZ twins reared apart).

Phenotypic Variance

• VP = VG + VE
• VP: phenotypic variance
• VG: genetic variance
• VE: environmental variance

Heritability Estimate

• The portion of the phenotypic (total) variance that is attributable to genetic variance.

History of Individual Differences Psychology

• A historically embedded science with roots in ancient Greece (Plato, Aristotle, Cicero, Hippocrates, and Galen).
• Focus on understanding individual differences and types.