Personality and Individual Differences: Physiological Approach to Personality

PHYSIOLOGICAL APPROACH TO PERSONALITY

References

Larsen, R.J., & Buss, D. M. (2021). Personality Psychology: Domains of Knowledge About Human Nature (7th Edition). McGraw-Hill. Chapter 7, pp. 184-221. 2024-2025 Konstanze Schoeps, PhD (she, her)

GROUP LEARNING OUTCOMES

• Students will understand the biological and physiological mechanisms underlying personality and individual differences.

E= mc2 SCIENCE ENGLISH MATH

PHYSIOLOGICAL APPROACHES TO PERSONALITY

Extraversion- Introversion Sensitivity to reward and punishment Sensation seeking Neuro- transmitters and Personality

THREE FUNDAMENTAL QUESTIONS

How does the physiological system influence personality? The nervous system (e.g., brain), cardiac system (e.g., heart), and musculoskeletal system (e.g., muscles) shape personality traits and responses. To what extent do differences in physiology create, contribute to, or indicate differences in psychological functioning? Physiological sensitivity varies among individuals-for example, some are irritated by loud noise, while others are unaffected-impacting psychological traits. Are physiological theories sufficient to explain and predict behavior? Physiological theories link traits to constructs like chemical imbalances (e.g., sensation- seeking), but other factors also shape behavior ..

WHY EXTRAVERTS LIKE MEETING NEW PEOPLE AND GET BORED EASILY WHILE INTROVERTS PREFER BEING ALONE OR WITH A FEW FRIENDS?

EXTRAVERSION - INTROVERSION

VB- ARAS AAP VB - Visceral brain AAP - Ascending afferent pathways ARAS - Ascending reticular activating system Fig. 5. Diagrammatic representation of the interaction between the limbic system (visceral brain) and the reticular-cortical arousal system. From Eysenck, 1967. Eysenck's biological theory of personality (1967)

• Core Idea: Eysenck proposed that personality traits like extraversion and introversion are linked to differences in the brain's Ascending Reticular Activating System (ARAS).
• Key Mechanism (ARAS): The ARAS acts as a gateway for sensory stimulation entering the brain's cortex.
• Introverts: More stimulation enters due to an open ARAS, leading to higher resting cortical arousal.
• Extraverts: Less stimulation enters due to a closed ARAS, resulting in lower resting cortical arousal.

EXTRAVERSION - INTROVERSION

Eysenck's biological theory of personality (1967)

Hebb's Optimal Arousal Theory (1955)

• Performance is best at an optimal arousal level, which varies by task:
• Too much arousal -> Overwhelmed, anxious, or overstimulated.
• Too little arousal -> Bored, disengaged, or drowsy.

Baseline Arousal Differences

High Performance quality Optimal level Boredom or apathy High anxiety Low Low High Arousal level

• Introverts: Higher baseline cortical arousal -> more often above the optimal arousal level.
• To regulate downwards, introverts avoid social stimulation and prefer quieter settings.
• Extraverts: Lower baseline cortical arousal -> more often below the optimal arousal level.
• To regulate upwards, extraverts seek stimulating activities and social interactions.
• The behaviors typically associated with introversion and extraversion reflect attempts to self-regulate arousal:
• Introverts -> Avoid overstimulation to reduce arousal.
• Extraverts -> Seek stimulation to increase arousal.

EXTRAVERSION - INTROVERSION

Eysenck's biological theory of personality - Update (1985)

Findings from Research

• Baseline Arousal Levels:
• Studies showed no significant differences in baseline cortical or autonomic nervous system activity between introverts and extraverts.
• Responsiveness to Moderate Stimulation:
• Introverts exhibit greater physiological reactivity (e.g., enhanced nervous system responses) compared to extraverts when exposed to moderate levels of stimulation (e.g., sensory input like noise, light, or social interactions).

Revised Theory

• The difference between introverts and extraverts lies in arousability, not baseline arousal levels.
• While introverts and extraverts may show similar brain activity at rest (e.g., while sleeping), introverts demonstrate heightened reactivity when stimulation levels rise.

EXTRAVERSION - INTROVERSION

Eysenck's biological theory of personality

Behavioral Implications

• Introverts: Restraint, quietness, and preference for solitary or low- stimulation settings stem from a need to manage overstimulation.
• Extraverts: Sociability, activity-seeking, and outgoing behavior are driven by the need to boost arousal levels.

Applications in Daily Life

• Education: Quiet study spaces may suit introverts, while collaborative or stimulating settings may benefit extraverts.
• Workplace: Customizing roles to match stimulation preferences (e.g., introverts in analytical tasks, extraverts in dynamic, people-facing roles).
• Mental Health: Understanding personality and arousal levels can guide strategies for managing stress and anxiety.

WHY SOME PEOPLE ARE MORE SUSCEPTIBLE TO ANXIETY ATTACKS, FEARS AND WORRIES WHILE OTHERS ARE SUSCEPTIBLE TO POSITIVE EMOTIONS AND SEEK OUT INTERACTING WITH OTHERS?

SENSITIVITY TO REWARD AND PUNISHMENT

Gray's reinforcement sensitivity theory (1972, 1990)

• Overview: Gray's model of personality is based on brain function research (animal studies) and focuses on two biological systems in the brain:

. Behavioral Activation System (BAS) -> Approach Motivation . Behavioral Inhibition System (BIS) -> Avoidance Motivation

• Key Idea: Personality differences arise from variations in individuals' sensitivity to reward and punishment cues, which are regulated by these systems.

R O C C O 0 C CS

SENSITIVITY TO REWARD AND PUNISHMENT

Gray's reinforcement sensitivity theory (1972, 1990)

Behavioral Activation System (BAS)

• Definition: BAS is responsive to incentives and reward cues. It regulates approach behavior and is likely linked to the dopamine system (pleasure, motivation).
• How It Works: When a rewarding stimulus is detected, BAS triggers behaviors to pursue the reward.
• Example: A child hears music from an ice cream truck (cue for reward) and runs toward it (approach behavior).
• Analogy: BAS acts like an accelerator, motivating a person to move toward goals or rewards.
• Individual Differences in BAS:
• People with a reactive BAS are especially sensitive to reward cues and predisposed to positive emotions (e.g., excitement, enthusiasm).
• As individuals with a reactive BAS approach a goal, their ability to inhibit behavior decreases, leading to impulsivity.

. BAS -> Impulsivity: High BAS sensitivity correlates with the personality dimension of impulsivity.

SENSITIVITY TO REWARD AND PUNISHMENT

Gray's reinforcement sensitivity theory (1972, 1990)

Behavioral Inhibition System (BIS)

• Definition: BIS is responsive to punishment, frustration, and uncertainty cues. It regulates avoidance behavior and inhibits ongoing actions.
• How It Works: When punishment cues are detected, BIS activates to stop or avoid behavior.
• Example: A child who has been punished for crossing the street without looking develops an avoidance response when seeing cars (punishment cue).
• Analogy: BIS acts like brakes, helping a person stop or avoid behaviors that might lead to negative outcomes.
• Individual Differences in BIS:

. People with a reactive BIS are highly sensitive to threats and punishment. . Such individuals are prone to negative emotions, including anxiety, fear, and sadness. . BIS -> Anxiety: High BIS sensitivity aligns with the personality dimension of anxiety. STOP

SENSITIVITY TO REWARD AND PUNISHMENT

BIS High N (neuroticism) EYSENCK'S PEN High anxiety (GRAY) BAS High impulsivity (GRAY) Low E (introversion) EYSENCK'S PEN High E (extraversion) EYSENCK'S PEN Low impulsivity (GRAY) Low anxiety (GRAY) Low N (emotional stability) EYSENCK'S PEN

Gray's reinforcement sensitivity theory (1972, 1990)

Extraversion and BAS

• Extraverts are highly sensitive to rewards and incentives (motivated to seek rewards).
• Reward sensitivity reflects the "wanting" of rewards, not necessarily their consumption (liking).

Neuroticism and BIS

• Neurotic individuals exhibit heightened sensitivity to threats, punishment, and uncertainty.
• This increased sensitivity leads to defensive behaviors and stress responses (e.g., cortisol release).

Impulsivity vs. Anxiety

• Impulsivity arises from high BAS activity (reward-driven behavior).
• Anxiety results from high BIS activity (threat sensitivity and avoidance)

WHY DO SOME PEOPLE SEEK OUT THRILLING EXPERIENCES, EVEN THOUGH SUCH EXPERIENCES MAY COME WITH CERTAIN RISKS?

SENSATION SEEKING

Zuckerman's theory of sensatin seeking (1965, 1978)

• Definition: Sensation seeking is the tendency to seek out thrilling, novel, and exciting activities, take risks, and avoid boredom.
• Origen: Sensory Deprivation Studies
• Participants placed in sensory-deprived environments (no light, sound, or tactile sensations).
• Feelings: relaxed -> bored -> anxious -> hallucinate.
• The brain compensates for the lack of input by generating its own activation (e.g., hallucinations).
• Key Finding: Individuals deprived of sensory input will actively seek any stimulation, even repetitive or "boring" content like stock market reports.

. Hebb's Theory: People are motivated to maintain an optimal level of arousal by seeking out tension and stimulation. . Sensation seekers need higher levels of stimulation to achieve this balance.

SENSATION SEEKING

Zuckerman's theory of sensatin seeking (1965, 1978)

Sensation Seeking Research

• Zuckerman observed that some people are extremely distressed by sensory deprivation.
• High sensation seekers:
• Found sensory deprivation intolerable.
• Requested more sensory material (e.g., tapes, books).
• Quit the experiments early.

Sensation Seeking in Daily Life

• Zuckerman developed a questionnaire to measure sensation-seeking tendencies.
• High sensation seekers often engage in:
• Risky behaviors: Skydiving, gambling.
• Thrilling activities: Volunteering for riot duty (police officers), participating in unusual psychological experiments.

Connection to Personality

• Strong positive correlation with extraversion.
• Sensation seekers display greater approach behaviors, searching for novelty and excitement.