Personality, Temperament, and Biological Foundations: Chapter 5 Study Guide

Personality and Temperament

Temperament: Definition and Dimensions

Temperament refers to biologically based emotional and behavioral tendencies that appear early in life and serve as the foundation for later personality development. The primary temperament dimensions are:

• Activity: Overall energy and movement level.

• Emotionality: Intensity of emotional reactions.

• Sociability: Preference for being around others.

These traits interact with experience to shape personality development over time.

Example: A child with high activity and sociability may be more outgoing and energetic, influencing their social experiences and personality growth.

Biological Models of Personality

Eysenck’s Model of Nervous System Arousal/Activation

Eysenck proposed that personality differences stem from how easily the nervous system becomes aroused. Introverts have higher baseline activation of the Ascending Reticular Activating System (ARAS), making them sensitive to overstimulation. Extroverts have lower baseline arousal, seeking stimulation. The neuroticism-stability dimension reflects autonomic nervous system activity—high neuroticism involves greater emotional reactivity.

• Introversion–Extraversion: Preference for lower or higher stimulation.

• Neuroticism–Stability: Degree of emotional reactivity and calmness.

Example: Introverts may avoid loud parties, while extroverts seek them out for stimulation.

Experimental Evidence for Brain Basis of Introversion/Extraversion

Research supports biological differences: introverts show stronger brain arousal and seek stimulation avoidance, while extroverts show lower reactivity and seek more excitement. Brain imaging also links extraversion to dopamine activity, explaining their reward-seeking behavior.

• Key Point: Introverts’ brains react more strongly to stimulation; extroverts’ brains crave it.

Gray’s Reinforcement Sensitivity Theory (BAS, BIS, FFFS)

Gray developed Reinforcement Sensitivity Theory, identifying three key systems:

• Behavioral Activation System (BAS): Sensitivity to reward and linked to dopamine; drives impulsivity.

• Behavioral Inhibition System (BIS): Sensitivity to punishment and avoidance; linked to anxiety and worry.

• Fight, Flight, Freeze System (FFFS): Responds to fear and threat.

Example: Individuals with a strong BAS may be more prone to risk-taking and impulsive behavior.

Genetic and Environmental Influences

Twin Studies: Genetic and Environmental Contributions

Twin studies (e.g., Minnesota Twin Study) compare identical (monozygotic) and fraternal (dizygotic) twins to estimate heritability. Identical twins are more similar in personality, even when raised apart, showing a strong genetic influence. Differences between twins raised together come from shared environmental experiences—unique life experiences.

• Heritability: The proportion of trait variation explained by genetic differences.

• Environmental influences: Unique experiences shape personality.

Example: Identical twins separated at birth may still show similar personality traits due to genetics.

Classical and Modern Theories

Jung and Pavlov’s Influence on Eysenck

Eysenck borrowed introversion/extraversion from Jung, and conditioning/arousal concepts from Pavlov. He integrated them by connecting psychological traits with biological nervous system processes, creating a scientific model of personality grounded in measurable nervous system activity.

• Jung: Personality types (introvert/extravert).

• Pavlov: Biological conditioning and arousal.

Contrast: Psychoanalytic vs. Scientific Approaches

Psychoanalytic theorists relied on case studies, interpretation, and introspection, which Eysenck viewed as unscientific. He favored empirical research, experiments, and statistical analysis, seeking objective, testable data about personality rooted in biology and measurable behavior.

• Psychoanalytic approach: Subjective interpretation.

• Scientific approach: Empirical, measurable, and testable.

Evolutionary Approaches to Personality

Basic Ideas Behind Evolutionary Psychology

Evolutionary psychology sees personality as a product of natural selection. Traits developed because they offered adaptive advantages in the environment of evolutionary adaptedness—such as cooperation, dominance, or risk-taking—which improve survival or reproduction. These are called evolved psychological mechanisms that shape how we think, feel, and behave today.

• Inclusive fitness: Evolutionary success measured by genes passed through relatives.

• Environment of evolutionary adaptedness: Ancestral environment shaping human traits.

• Evolved psychological mechanisms: Mental systems shaped by evolution for adaptive purposes.

Example: Social cooperation may have evolved because it increased group survival.

Key Terms and Definitions

Term	Definition
Heritability	The proportion of trait variation explained by genetic differences.
Temperament	Biologically based tendencies in emotion and behavior.
Activity	General level of energy or movement.
Emotionality	Intensity of emotional reactions.
Sociability	Tendency to seek social interaction.
Behavioral genomics	Study of how genes affect behavior.
Eysenck’s model of nervous system arousal/activation	Links brain arousal levels to introversion/extraversion.
Introversion–Extraversion	Preference for lower or higher stimulation.
Neuroticism–Stability	Degree of emotional reactivity and calmness.
Ascending Reticular Activating System (ARAS)	Brain system controlling cortical arousal.
Autonomic nervous system activation	Physiological arousal linked to emotional reactivity.
Gray’s Reinforcement Sensitivity Theory	Explains personality through reward, punishment, and threat systems.
Behavioral Activation System (BAS)	Reward sensitivity; approach behavior.
Behavioral Inhibition System (BIS)	Punishment sensitivity; avoidance and anxiety.
Fight, Flight, Freeze System (FFFS)	Fear-based threat response.
Impulsivity, fear, and anxiety/worry	Emotional traits tied to BAS, FFFS, and BIS.
Sensation seeking/addiction processes	Desire for novelty and stimulation; linked to dopamine.
Monozygotic and dizygotic twins	Identical and fraternal twins used in heritability studies.
Inclusive fitness	Evolutionary success measured by genes passed through relatives.
Environment of evolutionary adaptedness	Ancestral environment shaping human traits.
Evolved psychological mechanisms	Mental systems shaped by evolution for adaptive purposes.