Eysenck’s Theory Parts of Slideshow adapted from Dr Simon Boag

Lecture Outline I. Eysenck’s dimensional approach Extroversion vs introversion Extroversion vs introversion Neuroticism vs Stable Neuroticism vs Stable II. Biological basis of personality RAS & visceral brain (PNS) RAS & visceral brain (PNS) III. Summary & evaluation

Learning Outcomes After this lecture you should be able to: Understand & explain the meaning of personality ‘type’, ‘trait’ & ‘dimension’ Understand & explain the meaning of personality ‘type’, ‘trait’ & ‘dimension’ Describe & explain ‘extroversion’, ‘introversion’, ‘neuroticism’ & ‘stable’ Describe & explain ‘extroversion’, ‘introversion’, ‘neuroticism’ & ‘stable’ Describe & explain Eysenck’s biological explanation for personality differences Describe & explain Eysenck’s biological explanation for personality differences

Types & Traits Traits: An enduring characteristic of a person’s behavior eg. sociable/unsociable Types: A class of individuals with common characteristic or pattern of characteristics (physical/psychological) eg. Sheldon (1942) Varieties of Temperament

Personality Types Hippocrates (460?-377?BC) & Galen ( ? AD): personality based on humors Hippocrates (460?-377?BC) & Galen ( ? AD): personality based on humors Sanguine (blood) Warm-hearted, optimistic Warm-hearted, optimistic Melancholic (black bile) Sad, depressed, anxious Sad, depressed, anxious Choleric (yellow bile) Quick tempered, angry, assertive Quick tempered, angry, assertive Phlegmatic (phlegm) Slow, lethargic, calm Slow, lethargic, calm

Eysenck’s Theory of Personality Hans Eysenck ( )

Eysenck’s Approach Identifying universal, measurable dimensions of personality Identifying universal, measurable dimensions of personality Rejects unique individual: “… the unique individual is simply the point of intersection of a number of quantitative variables” (Eysenck, 1952, p.18). Rejects unique individual: “… the unique individual is simply the point of intersection of a number of quantitative variables” (Eysenck, 1952, p.18). Identified through large scale assessment Identified through large scale assessment eg. US Airforce personnel eg. US Airforce personnel Statistical approach: Factor analysis Statistical approach: Factor analysis

Eysenck’s Personality Types (1) Extrovert (2) Introvert (3) Neurotic (4) Stable

Personality Dimensions (1): Introversion/Extroversion Adapted from Jung’s types Extrovert: Outgoing, embraces the world, responsive to social & physical stimulation Outgoing, embraces the world, responsive to social & physical stimulation Insensitive to stimulation (‘stimulus hungry’) Insensitive to stimulation (‘stimulus hungry’) Introvert: Hesitant, reflective, withdraws from social & physical stimulation Hesitant, reflective, withdraws from social & physical stimulation Sensitive to stimulation (‘stimulus shy’) Sensitive to stimulation (‘stimulus shy’)

Extroversion/Introversion Dimension : relative degree (more or less) Dimension : relative degree (more or less) Introvert X Y Z Extrovert Extrovert: sociable, outgoing, interactive, expressive, sensation seeking, acts first, think later, dislikes being alone Extrovert: sociable, outgoing, interactive, expressive, sensation seeking, acts first, think later, dislikes being alone Introvert: private, reclusive, reserved, quiet, inward, sensitive, thinks before acting, exhausted by groups Introvert: private, reclusive, reserved, quiet, inward, sensitive, thinks before acting, exhausted by groups

Personality Dimension (2): Neuroticism/Normality High degree of neuroticism: More emotionally reactive More emotionally reactive eg. moody, tense, anxious, irritable eg. moody, tense, anxious, irritable High degree of stability: Less emotionally reactive (but still have emotions) Less emotionally reactive (but still have emotions)

Dimensions: Persons X & Y Introversion/Extroversion: Intr. X Y Extr. Neuroticism/Stable: Neur. Y X Stable These dimensions are orthogonal These dimensions are orthogonal

II. The Biological Basis of Personality Personality types result from differences in central nervous system (CNS) functioning Personality types result from differences in central nervous system (CNS) functioning Implications: Genetic basis of personality Genetic basis of personality Relatively stable & unchanging Relatively stable & unchanging However: environment interacts with biological predispositions However: environment interacts with biological predispositions

Biological Basis of Extroversion/Introversion RAS system: Reticular Activation System Reticular Activation System Cortical excitation & inhibition Cortical excitation & inhibition High RAS arousal: Predisposes to introversion Predisposes to introversion Low RAS arousal: Predisposes to extroversion Predisposes to extroversion Evidence: Introverts have higher sedation threshold than extroverts (cf. ADHD)

Central Nervous System (CNS)

Peripheral Nervous System (PNS)

Parasympathetic Nervous System (Slow Down)

Sympathetic Nervous System (Speed Up)

Extroverts: Low RAS arousal Low RAS arousal

Introverts: High RAS arousal High RAS arousal

Neurotics High Sympathetic Response (PNS) High Sympathetic Response (PNS)

Stable High Parasympathetic Response (PNS) High Parasympathetic Response (PNS)

Biological & Environmental Interaction “Biological causes act in such a way as to predispose an individual in certain ways to stimulation; this stimulation may or may not occur, depending on circumstances which are entirely under environmental control” (Eysenck, 1967, pp ) Effect of different teaching environments Effect of different teaching environments

III. Evaluation Twin studies: E & N: 50% genetic Twin studies: E & N: 50% genetic Adoption studies: Correlations b/w adoptive parents & adopted children for E & N are around 0% Adoption studies: Correlations b/w adoptive parents & adopted children for E & N are around 0% E, N & P: highest validity of all traits (Kline, 1993) E, N & P: highest validity of all traits (Kline, 1993) Contradictory findings (eg. sedation findings) Contradictory findings (eg. sedation findings) Hypothesised brain areas are not independent of one another Hypothesised brain areas are not independent of one another

Summary Eysenck’s approach identifies personality dimensions (ext/int; neu/nor) Eysenck’s approach identifies personality dimensions (ext/int; neu/nor) A person’s placing on these dimensions determines their personality temperament A person’s placing on these dimensions determines their personality temperament Eysenck proposes a biological basis for personality Eysenck proposes a biological basis for personality Extroversion & introversion are said to be related to RAS functioning Extroversion & introversion are said to be related to RAS functioning Neuroticism & normality are said to be related to visceral brain activity (PNS) Neuroticism & normality are said to be related to visceral brain activity (PNS)