IDAP - L6/L7

Individual Differences in Psychology

• Individual differences refer to the variability between people on specific traits, such as personality, cognitive abilities, and emotional responses.
• Traits are long-lasting, stable ways of thinking, feeling, and behaving, while states are short-term, emotional, or cognitive perspectives that vary across time and situations.

Aims of Individual Differences Research

• Describe how people differ on psychological traits
• Identify the mechanisms and causes of these differences
• Investigate the impact of these differences on people's lives

Psychometrics

• Psychometrics is the field of psychology concerned with psychological measurement, including developing, administering, and scoring tests that assess psychological traits.
• Key characteristics of psychometrics include:
  • Providing a sample of behavior
  • Providing an objective indicator of behavior
  • Obtained under standardized conditions
  • Provides established rules for scoring

Error in Psychological Tests

• Error in psychological tests refers to the difference between a participant's score on a test and their "true" score.
• There are two main types of error:
  • Unsystematic error: random and no pattern between them
  • Systematic error: constant and repeatable, arising from administration, situational factors, scoring problems, or the test itself

Reliability

• Reliability refers to the accuracy, reproducibility, and consistency of a measurement.
• Types of reliability include:
  • Internal consistency: whether individual items on a test measure the same concept
  • Test-retest reliability: whether the same test provides consistent results over time
  • Inter-rater reliability: the agreement between assessors

Validity

• Validity refers to whether a test measures what it is supposed to measure.
• Types of validity include:
  • Face validity: whether a test focuses on what it is supposed to measure
  • Content validity: whether a test adequately assesses all dimensions it is supposed to
  • Criterion validity: how strongly correlated a test is to a criterion it is measuring
  • Construct validity: how accurately a test measures a theoretical construct

Personality Traits

• Personality traits are relatively stable patterns of thinking, feeling, and behaving.
• Allport (1961) defined personality as a dynamic, internal system influenced by psychophysical factors.
• Main goals of personality research:
  • How people differ in terms of personality
  • Why people differ
  • What impact these differences have on people's lives

Trait Theories of Personality

• Trait theories assume that:
  • Traits are consistent over time
  • Traits occur consistently across groups of people
  • Traits can be reliably assessed
• Main assumptions of personality traits:
  • Influence behavior
  • Relatively stable over time
  • Relatively stable across situations

Dimensions of Personality

• Dimensions refer to scales with cut-off points that attempt to define personality in terms of the degree to which a person possesses a variety of traits.
• Lexical approaches to personality assume that individual differences in personality traits are encoded in everyday language.

Factor Analytics Approaches

• Factor analytics approaches involve more advanced investigations of the basic number of personality traits.
• Multivariate data reduction is used to simplify relationships between many variables.
• Two main types of factor analytics:
  • Exploratory data-driven factor analysis
  • Confirmatory/theory-driven factor analysis

Big Five Personality Traits

• The Big Five personality traits are extraversion, agreeableness, conscientiousness, neuroticism, and openness to experience.
• Each trait is dimensional, and measured on a scale.
• The Big Five Inventory is a widely used measure of personality.

Criticisms of the Big Five

• Criticisms include:
  • Limited evidence for an evolutionary origin of personality
  • Correlations between personality studies can result from how items are measured
  • People tend to select answers closer to the most socially desirable one

Life Outcomes Predicted by Personality

• Personality traits are associated with various life outcomes, including:
  • Educational attainment
  • Work/career success
  • Health

Stability of Personality

• Personality traits become more consistent with age, peaking at 50-59 years.
• Throughout adulthood, neuroticism, openness, and extraversion decline, while agreeableness and conscientiousness increase.

Myers-Briggs Personality Indicator

• The Myers-Briggs Personality Indicator is a popular test that assigns people to one end of each of four scales.
• Criticisms of the test include:
  • Not comprehensive
  • Not reliable
  • Not valid

Genetic Variation and Behavioural Genetics

• Genetic variation refers to the differences in DNA sequence between people.
• Single nucleotide polymorphisms (SNPs) are the most common type of genetic variation.
• Behavioural genetics investigates the relationship between genes, environment, and behaviour.

Heritability

• Heritability is the degree of variability in a trait that is due to genetic differences between people.
• Heritability estimates are used to quantify the genetic component of a trait.

Types of Studies in Behavioural Genetics

• Family studies
• Twin studies
• Adoption studies
• Reared-apart studies

Limitations of Behavioural Genetics Studies

• The additive assumption is an oversimplification of variability
• Heritability does not directly measure environmental effects
• Twin studies can overestimate genetic effects
• Participants in adoption studies are often non-representative of the general population