PSYC231 Personality: Background of Trait Theory and Historical Perspectives

The Concept and Definition of Traits

• Definition of Traits: Traits are understood as general dispositions possessed by individuals that uniquely influence their cognition and behavior. Examples include being outgoing, impulsive, anxious, sociable, or hostile.

• Inference of Traits: According to McCrae et al. ($2000$, p.$175$), "Traits cannot be directly observed, but rather must be inferred from patterns of behaviour and experience that are known to be valid trait indicators."

• Trait versus State:

  • States: Refer to the condition, intensity, centrality, or arousal of corresponding traits at a specific point in time. For instance, moods are considered states of emotive traits.

  • Traits: Relatively stable characteristics over time and across different situations, though they may fluctuate or drift.

• The Descriptive vs. Explanatory Debate: A key debate in the field is whether traits merely describe people's personalities (labeling patterns) or whether they actually explain the underlying causes of personality.

• Personality Type vs. Personality Trait:

  • Personality Type: Individuals are placed into discrete, non-overlapping categories. This is not the dominant perspective in modern research.

  • Personality Trait: A continuous dimension where individuals are placed along a spectrum. This allows for "shades of grey" and is currently the dominant perspective.

General Assumptions of Trait Theories

• Universal Possession: Every human possesses all traits, but they differ in terms of intensity or the importance of those traits to the individual.

• Developmental Timeline: Trait development is traditionally assumed to conclude by early adulthood.

• Dimensional and Hierarchical Arrangement: Personality elements tend to be arranged on a continuum (dimensionally) and organized in a hierarchy.

• Orthogonality (Independence): These dimensions are generally assumed to be independent of one another.

• Parsimony vs. Accuracy: Researchers attempt to find a "simple structure" of personality, balancing the need for parsimony (simplicity) with descriptive accuracy.

• Stability: Traits are relatively stable across time and situations, noting that they can experience minor fluctuations or drifts.

Forces Shaping Personality and Meta-Theoretical Assumptions

• Forces of Personality:

  • Biology & Genetics: Relates to psychophysiology.

  • Evolution: Includes evolutionary personality psychology and behavioral genetics. This perspective posits that human psychology evolved to solve adaptive problems.

  • Environment: Factors include familial, social, cultural, and natural surroundings.

• Meta-Theoretical Assumptions:

  • Knowability: Personality is a topic that can be known and studied via scientific methods.

  • Rationality: Despite inherent biases, humans are generally capable of understanding themselves (a point notably disputed by the psychodynamic tradition).

  • Variability: Individuals differ from each other in significant, measurable ways.

  • Proactivity: The locus of causation for human behavior is found within the person (historically disputed by some social psychologists).

Methodologies for Measuring Traits

• Standardized Psychometric Questionnaires (Self-Reports): Utilizing validated instruments to reliably measure psychological constructs.

• Factor Analysis: A statistical method used to identify underlying dimensions or factors in behavior and personality.

• Reliability & Validity Assessments: These ensure consistency in measurement and that the tool accurately captures the intended construct.

• Life Histories: Narratives used to understand the developmental trajectory of an individual.

• Peer Assessments & Interviews: Gathering multiple outside perspectives to improve the understanding of individual differences.

• Neuroscientific Measures: Using Brain Scans and EEG to examine neural activity and structural brain correlates.

• Physiological Measures: Monitoring bodily responses, such as Heart Rate, to assess stress and emotional factors.

• Genetic Studies: Using Twin and Adoption Studies to explore the balance of genetic versus environmental contributions to personality.

Historical Perspectives: Humoural Theory and Physiognomy

• Humoural Theory:

  • Developed by Hippocrates (around $400~BCE$) and later expanded by Galen.

  • Personality was linked to four bodily fluids called "humours."

  • Blood: Associated with the Sanguine temperament (optimistic, social).

  • Yellow Bile: Associated with the Choleric temperament (ambitious, irritable).

  • Black Bile: Associated with the Melancholic temperament (thoughtful, melancholic). The word "Melancholy" comes from the Greek melas (black) + khole (bile).

  • Phlegm: Associated with the Phlegmatic temperament (calm, relaxed).

  • Significance: The balance of these humours was thought to be essential for physical and mental health; it laid the foundation for modern trait theory.

• Physiognomy:

  • Definition: The belief that character and personality traits can be inferred from facial features.

  • Modern View: Psychology acknowledges only limited, subtle correlations. Links are probabilistic, not deterministic.

  • Biological Links: Testosterone levels can influence facial structure (e.g., a pronounced jawline), which may correlate with traits like assertiveness, dominance, and competitiveness.

Historical Perspectives: Phrenology and Somatotypes

• Phrenology:

  • Definition: The belief that personality traits are determined by the shape and bumps of the skull.

  • Core Concepts: The brain was thought to be divided into specialized "organs" for traits like benevolence, combativeness, or spirituality. Bumps or depressions on the skull supposedly indicated the strength or weakness of these traits.

  • Current Status: Discredited as a pseudoscience, though it was an early historical attempt to localize psychological functions in the brain.

• William Sheldon’s Somatotypes ($1898\text{--}1977$):

  • Sheldon, educated in psychology and medicine in the $1920s$ and $1930s$, studied the relationship between physique, psychology, and delinquency. He famously analyzed $4000$ nude posture photos of Ivy League freshmen between the $1940s$ and $1970s$.

  • Endomorphic Body: Soft body, round shape, over-developed digestive system, and underdeveloped muscles.

    • Traits: Love of food, sociable, relaxed, tolerant, even emotions, need for affection, good-humored.

  • Mesomorphic Body: Hard, muscular, rectangular shape, thick skin, upright posture.

    • Traits: Adventurous, desire for power/dominance, courageous, competitive, assertive, bold, love of risk, indifferent to others' opinions.

  • Ectomorphic Body: Thin, flat chest, delicate build, tall, lightly muscled, large brain, young appearance.

    • Traits: Self-conscious, introverted, socially anxious, artistic, mentally intense, preference for privacy, emotionally restrained.

Dimensional Models: Wundt and Eysenck

• Wilhelm Wundt’s Two-Dimensional Model (Late $1800s$):

  • Characterized personality by two core dimensions:

    1. Emotionality (Strength of Emotions): Strong (emotional/excitable) vs. Weak (calm/stable).

    2. Changeability vs. Stability: Easily changing (flexible/adaptable) vs. Stable (consistent/predictable).

  • This dimensional approach influenced Hans Eysenck and the development of the Big Five.

• Eysenck’s Integration (Based on Eysenck & Eysenck, $1958$):

  • Dimensions: Introverted vs. Extraverted and Emotionally Unstable (Neurotic) vs. Emotionally Stable.

  • Mapping Traditional Humours to Modern Dimensions:

    • Melancholic: Unstable + Introverted (Moody, Anxious, Rigid, Reserved, Unsociable).

    • Choleric: Unstable + Extraverted (Aggressive, Excitable, Impulsive, Active, Touchy).

    • Phlegmatic: Stable + Introverted (Passive, Careful, Thoughtful, Peaceful, Controlled, Reliable).

    • Sanguine: Stable + Extraverted (Sociable, Outgoing, Talkative, Responsive, Easygoing, Lively).

The Lexical Approach and Gordon Allport

• The Lexical Hypothesis: Proposed by Sir Francis Galton ($1822\text{--}1911$). It suggests that if individual differences are important, they will eventually be encoded in language as trait-descriptors.

  • Importance Indicators: The frequency of word use and the number of synonyms indicate the importance of a trait. Cross-cultural presence indicates universality.

  • Synonym Density: "Honest" has many synonyms (e.g., trustworthy, moral, ethical, upright), indicating high importance. "Pedantic" has fewer synonyms (e.g., fussy, meticulous), indicating lower relative importance.

• Gordon Allport ($1897\text{--}1967$):

  • Extended the lexical hypothesis and identified over $4,500$ traits.

  • Viewed traits as real physical structures in the nervous system that would eventually be discovered.

  • Adopted an idiographic focus, believing each individual has a unique set of traits.

  • Hierarchy of Traits:

    • Cardinal Trait: Dominates a person's entire personality and creates specific needs.

    • Central Traits: Characteristics that define a person's daily interactions.

    • Secondary Traits: Traits exhibited only in specific situations or preferences.

• Evaluation of Allport:

  • Pros: Founder of the academic field of personality (separated it from psychopathology); developed the Trait and Lexical approaches; his "Core/Secondary" distinction foreshadowed "Source traits."

  • Cons: Failed to develop a standardized measurement to assess all identified components collectively; actively ignored psychopathology; having over $4,500$ traits is considered impractical for scientific application.

Timeline of Landmark Trait Theories

• $1920s$: Allport (Lexical Theory).

• $1940s$: Cattell.

• $1950s$: Sullivan (Interpersonal Theories).

• $1960s$: Norman (Lexical), Eysenck (Psychobiological), Leary (Interpersonal).

• $1980s$: Goldberg (Lexical), Gray (Psychobiological), Hazan & Shaver (Interpersonal).

• $1990s$: Costa & McCrae (Lexical), Zuckerman (Psychobiological), Cloninger (Psychobiological), Buss (Evolutionary), Wiggins (Interpersonal), Bartholomew (Interpersonal).

• $2000s$: Millon (Psychobiological), Gosling (Evolutionary).