Trait and Biological Theories

Trait and Biological Theories

• Learning Goal 1.2: Discuss the role that biology plays in determining personality and behavior.

Evolutionary Perspective on Personality

• Evolutionary theory:
  • Random mutations and variations occur among offspring.
  • Offspring compete for mates and resources.
  • Beneficial mutations/variations that improve survival/reproduction are passed to the next generation.
  • Over time, more of the population inherits these beneficial variations.
• Evolutionary approach focuses on similarities in personalities (why certain traits are common due to their advantages for survival).

Biological Perspective on Personality

• Focuses on explaining differences through heritability.
• Heritability: How much of the variation among a population’s traits can be attributed to genetics.
• Heritability cannot explain how much of a single person’s traits are genetic vs. learned; it applies at a population level.

Trait Theories of Personality

• Trait theories describe personality based on broad traits (e.g., extraversion).
• Idiographic theories: emphasize each person’s unique traits.
• Nomothetic theories: quantify a given set of specific traits in each person.
• Trait and biological theories are merging: trait theories describe differences, and researchers seek biological variables causing those differences.
• Trait theories DESCRIBE personality differences, while biological theories EXPLAIN them.

Trait Meets Biological

• Introverts:
  • Acetylcholine Pathway.
  • Reticular Activating System: More sensitive to stimulation, so distractions are overwhelming.
  • Hypothalamus: Triggers the parasympathetic nervous system to conserve energy, lowering heart rate and blood pressure in unfamiliar settings.
• Extroverts:
  • Dopamine Pathway.
  • Reticular Activating System: Less reactive, needing more stimulation, and seek new/exciting things.
  • Hypothalamus: Triggers the sympathetic nervous system in hectic environments, activating the "fight or flight" response, increasing heart rate and blood pressure.

The Timeline of Trait Theories

• Gordon Allport (1920s):
  • Original developer of the trait perspective and analysis of individual differences.
  • Cardinal traits: traits that best define you.
  • Central traits: traits you consistently display.
  • Secondary traits: traits you sometimes display.
• Raymond Cattell (1950s):
  • Developed “factor analysis” – a statistical technique identifying traits based on coinciding behaviors.
• Hans and Sybil Eysenck (1960s):
  • Identified 3 dimensions of personality (PEN: psychoticism, extraversion, neuroticism) and claimed they were genetically determined.

The Big Five

• Paul Costa and Robert McCrae (2000s):
  • Identified five traits that accurately predict behavior:
    • Conscientiousness (careful, disciplined, organized).
    • Agreeableness (gentle, trusting).
    • Neuroticism (anxious, vulnerable).
    • Openness (imaginative, spontaneous).
    • Extraversion (sociable, outgoing).
  • Traits are mostly stable across lifespan (openness decreases slightly, and agreeableness increases slightly).
  • Overall 50% heritable

Openness

• High Score: Curious, wide range of interests, independent.
• Low Score: Practical, conventional, prefers routine.

Conscientiousness

• High Score: Hardworking, dependable, organized.
• Low Score: Impulsive, careless, disorganized.

Extroversion

• High Score: Outgoing, warm, seeks adventure.
• Low Score: Quiet, reserved, withdrawn.

Agreeableness

• High Score: Helpful, trusting, empathetic.
• Low Score: Critical, uncooperative, suspicious.

Neuroticism

• High Score: Anxious, unhappy, prone to negative emotions.
• Low Score: Calm, even-tempered, secure.

Trait-Based Personality Assessments

• Personality inventories: True/false or multiple-choice questions to reveal feelings, attitudes, and behaviors.
• Most commonly used: Minnesota Multiphasic Personality Inventory (MMPI-2); assesses “abnormal” personality traits using empirically derived items.
  • Examples:
    • “I wake up fresh and restored in the mornings.”
    • “I wish I could be as happy as others seem to be.”
    • “I sometimes keep on at a thing until others lose their patience.”
    • “The future is too uncertain for a person to make serious plans.”

Other Predictors of Personality Traits?

• Social media posts can indicate personality traits.
  • Examples:
    • Achievements.
    • Political or intellectual ideas.
    • Infrequent posting.
    • Significant other.
• Colleges and employers sometimes check social media profiles, raising implications for social media use.

Trait/Biological Strengths and Limitations

• Strengths:
  • Explains why personality traits often run in families.
  • Inventories are quick, easy, and objective to score.
• Limitations:
  • Doesn’t consider situational changes in personality (the person-situation controversy).
  • Inventories rely on accurate and honest self-reporting.
  • Deterministic – ignores free will in personality development.