Hans Eysenck’s Biologically Based Factor Theory

Biologically Based Trait Theory

personality theory that emphasizes the biological and genetic basis of personality traits, unlike previous theories that downplayed or ignored biological influences.

• Extraversion/Introversion

• Neuroticism/Stability

• Psychoticism/Superego

Eysenck proposed 3 biologically based dimensions: ________—derived using both factor analysis and biology.

genetic differences

According to Eysenck, __ cause structural variations in the central nervous system, leading to individual differences in personality traits.

Temperament

A biologically based tendency to behave in specific ways from early in life; influenced by prenatal factors such as fetal heart rate and maternal stress.

Behavioral Genetics

The scientific study of heredity’s role in behavior, using methods like twin-adoption studies and gene-by-environment interaction research to assess heritability.

Heritability

The degree to which a trait or behavior is influenced by genetics; explored through research on identical/fraternal twins and adopted individuals.

Gene-by-Environment Interaction

A research method that examines how genetic differences interact with environments to produce behavior in some individuals but not others.

EEG (Electroencephalography)

A brain imaging method that records electrical activity in the brain using electrodes on the scalp; shows when brain activity occurs, but not precisely where.

fMRI (Functional Magnetic Resonance Imaging)

A brain imaging method that detects where brain activity occurs by tracking blood oxygen levels during tasks; shows which brain areas are most active

insufficient

Hans Eysenck believed that psychometric sophistication alone __ for understanding personality structure unless the identified dimensions also have biological evidence

1st Criterion for Identifying a Factor

The factor must have psychometric evidence, including being reliable and replicable across independent studies and laboratories.

2nd Criterion for Identifying a Factor

The factor must demonstrate heritability and conform to a genetic model, thereby excluding learned traits like mimicry or belief systems

3rd Criterion for Identifying a Factor

The factor must be theoretically meaningful, fitting logically within an existing theoretical framework developed through a deductive method

4th Criterion for Identifying a Factor

The factor must possess social relevance, meaning it should be related to real-world outcomes like addiction, injuries, performance, psychosis, or criminality.

Eysenck's Four-Level Hierarchy of Behavior

A structure of behavior organization including:

1. Specific Acts or Cognitions – isolated behaviors/thoughts

2. Habitual Acts or Cognitions – consistent behaviors across situations

3. Traits – semi-permanent dispositions made up of related habits

4. Types or Superfactors – clusters of interrelated traits forming broader personality types

Specific Acts or Cognitions (Level 1)

Individual behaviors or thoughts that may or may not reflect the person's typical actions

e.g., finishing a reading assignment once.

Habitual Acts or Cognitions (Level 2)

Regular, repeated behaviors under similar conditions;

for instance, consistently finishing assignments reflects a habitual response.

Traits (Level 3)

Defined as “important semi-permanent personality dispositions,” formed from clusters of habitual behaviors, and identified through factor analysis

Types or Superfactors (Level 4)

Broad personality categories made up of interrelated traits,

e.g., the introverted type may include persistence, social shyness, and poor emotional adjustment.

superfactors (types)

Hans Eysenck focused on at ___ the fourth level of the personality hierarchy (3 dimensions)

trait level (third level)

while Raymond Cattell worked at the ___, identifying 35 traits.

Eysenck's Three Personality Dimensions

1. Extraversion (E)

2. Neuroticism (N)

3. Psychoticism (P)

Bipolar Nature of Eysenck’s Factors

Each factor is bipolar:

• Extraversion (E) ↔ Introversion

• Neuroticism (N) ↔ Stability

• Psychoticism (P) ↔ Superego Function

Distribution of Eysenck’s Personality Traits

Traits like extraversion are unimodally distributed, meaning most people fall near the center of the scale, forming a bell-shaped curve (like height or intelligence).

biological foundation

Eysenck argued that E, N, and P have a strong ___, unlike traits like agreeableness and conscientiousness from the Five-Factor Model, which he said lack biological grounding.

Theoretical Support for Eysenck’s Factors

• Extraversion (E): Supported by Carl Jung

• Neuroticism (N): Emphasized by Sigmund Freud

• Psychoticism (P): Aligns with Maslow’s idea of health ranging from self-actualization to psychosis

Social Relevance of Eysenck’s Factors

Eysenck linked E, N, and P to real-world behaviors such as:

• Drug use

• Sexual behavior

• Criminality

• Disease prevention (e.g., cancer, heart disease)

• Creativity

Hans Eysenck’s View on the Five-Factor Theory

He acknowledged extraversion and neuroticism as valid across theories but criticized other Five-Factor traits (e.g., agreeableness) for lacking biological support

Eysenck vs. Jung on Extraversion

• Jung: Extraverts have an objective worldview; introverts, a subjective one.

• Eysenck: Focuses on behavioral traits like sociability and impulsiveness for extraverts; introverts are quiet, reserved, and cautious.

Eysenck on Extraversion

Focuses on behavioral traits like:

• Extraverts: sociability and impulsiveness

• Introverts: quiet, reserved, and cautious.

Jung on Extraversion

Extraverts have an objective worldview; introverts, a subjective one

Extraverted Personality Traits (Eysenck)

What personality trait are these?

• Sociable

• Impulsive

• Lively

• Quick-witted

• Jocular

• Optimistic

• Active

• Reward-seeking

Introverted Personality Traits (Eysenck)

What personality trait are these?

• Quiet

• Passive

• Unsociable

• Careful

• Thoughtful

• Pessimistic

• Sober

• Controlled

Biological Basis of Extraversion

Differences between extraverts and introverts are rooted in cortical arousal levels, a mostly inherited trait.

Cortical Arousal in Extraverts

• Low baseline arousal

• High sensory threshold

• Seek more stimulation (e.g., social events, extreme sports, substance use)

Cortical Arousal in Introverts

• High baseline arousal

• Low sensory threshold

• Avoid overstimulation; prefer calm, controlled environments

Extraverts

They habituate quickly (e.g., sexual or thrilling experiences), requiring increasing stimulation to maintain interest.

Introverts

They are less likely to tire of routine activities and remain over time.

Neuroticism (Factor N)

A superfactor indicating emotional instability.

Neuroticism (Factor N)

High scorers of this tend to overreact emotionally, struggle to return to baseline, and may report physical and psychological complaints.

genetic components

Eysenck found that anxiety, hysteria, OCD, and antisocial behaviors like crime and alcoholism have strong ___, especially among identical twins.

Biological Basis of Neuroticism

Linked to a highly reactive limbic system, especially the amygdala and hypothalamus, causing increased emotional sensitivity and reactivity

Neuroticism and Physical Symptoms

High N scorers often report physical problems (e.g., headaches, back pain) and vague psychological issues (e.g., worry, anxiety)

Diathesis-Stress Model (Eysenck's View)

Suggests neurotic disorders arise from the interaction of a biological vulnerability (diathesis) and environmental stress.

• High N scorers need less stress to develop symptoms.

Independence of N and E Factors

Eysenck’s factor analysis assumes zero correlation between neuroticism (N) and extraversion (E). They form independent axes

Neuroticism + Introversion = ?

Anxious, depressed, phobic, obsessive traits (e.g., Person A in Eysenck’s diagram).

Neuroticism + Mid-level Extraversion = ?

Prone to hysteria, suggestibility, and somatic symptoms (e.g., Person B).

Neuroticism + Extraversion = ?

May exhibit psychopathic tendencies, criminality, and delinquency (e.g., Person C)

Introversion + Stability = ?

Quiet and introspective, yet psychologically resilient (e.g., Person E).

normal distribution

Like , neuroticism scores follow a __. Extreme scores (high or low) are less common.

Psychoticism (Factor P)

A bipolar personality dimension ranging from psychoticism (hostile, egocentric, antisocial traits) to superego (caring, social, empathetic traits).

High Psychoticism Traits

What traits are these?

• Egocentric

• Cold

• Impulsive

• Hostile

• Aggressive

• Suspicious

• Psychopathic

• Antisocial

• Nonconforming

Low Psychoticism (Superego Traits)

• Altruistic

• Empathetic

• Cooperative

• Conforming

• Caring

• Socialized

• Conventional

Diathesis-Stress Model for Psychoticism

People high in P and under stress are more vulnerable to psychotic disorders.

High P = lower threshold for stress-induced psychotic breaks

Biological Basis of Psychoticism

Eysenck hypothesized a genetic predisposition for high P scorers to develop psychotic illnesses under stress, though less biologically supported than E and N.

Independence of P Factor

Psychoticism is independent of both extraversion (E) and neuroticism (N).

All three are orthogonal (at right angles), allowing for three-dimensional personality profiling

3D Model of Personality (Eysenck)

Personality can be mapped in 3-dimensional space using scores on E, N, and P. Each person has a unique coordinate

(e.g., Person F = high superego, moderate extraversion, average neuroticism).

Maudsley Personality Inventory (MPI)

Developed in 1959; measured Extraversion (E) and Neuroticism (N). Showed some correlation between E and N.

Eysenck Personality Inventory (EPI)

Developed to measure E and N independently (near-zero correlation); includes a Lie (L) scale to detect faking

Eysenck Personality Questionnaire (EPQ)

Introduced in 1975 to measure all three superfactors: P, E, and N; includes adult and junior versions.

genetics, biology, and experience

Eysenck’s model suggests that P (Psychoticism), E (Extraversion), and N (Neuroticism) interact with _,_, and _ to predict social behaviors—including those linked to health and disease.

lower

Extraverts have __cortical arousability, needing more external stimulation.

higher

Introverts have __ cortical arousability, making them more sensitive to stimuli and learning conditions

lung cancer

Low neuroticism (N) scorers, who tend to suppress emotions, were found to have a higher risk of developing __j than high N scorers

Personality Types and Disease

• Type I: Hopeless/helpless, nonemotional → Higher cancer risk

• Type II: Angry, aggressive, emotionally aroused → Higher heart disease risk

• Type III: Ambivalent (switching between Type I & II) → Low disease risk

• Type IV: Autonomy-focused → Low disease risk