AP Psychology: Biological Bases of Behavior - Comprehensive Notes

Neuron Structure

  • Basic Components:

    • Dendrites: Receive signals.

    • Cell body: Contains the nucleus.

    • Axon: Transmits signals.

    • Axon terminal: Releases neurotransmitters.

    • Synapse: Junction between neurons.

  • Axon Features:

    • Axon hillock: Where the axon originates from the cell body.

    • Myelin sheath: Insulating layer around the axon (formed by Schwann cells).

    • Node of Ranvier: Gaps in the myelin sheath.

  • Synapse Types:

    • Axodendritic: Axon to dendrite.

    • Axoaxonic: Axon to axon.

    • Synaptic cleft: Space between neurons at a synapse.

  • Neurotransmission:

    • Neurotransmitter: Chemical messenger.

    • Receptor: Binds neurotransmitters.

Glands

  • Endocrine Glands:

    • Pineal gland

    • Thyroid: Regulates metabolism; located in the thyroid cartilage of the larynx; parathyroid glands are on its posterior side.

    • Adrenal glands

    • Pancreas

    • Ovaries (female)

    • Testes (male)

    • Pituitary gland

    • Uterus

    • Thalamus

Brain Regions

  • Prefrontal Cortex:

    • Prefrontal cortex

    • Ventromedial prefrontal cortex

    • Medial prefrontal cortex

    • Amygdala

    • Hippocampus

    • Anterior Cingulate Cortex

Nature vs Nurture Debate

  • Central Question: To what extent do genes (nature) and environment (nurture) influence behavior?

  • Nature Perspective:

    • Genetics determine behavior.

    • Individuals are "born that way."

    • Innate characteristics exist.

    • Examples: physical traits (eye color, height) and some behavioral tendencies.

  • Nurture Perspective:

    • Environment, upbringing, and experiences determine behavior.

    • Examples: parenting styles, cultural background, educational experiences.

Historical Context

  • Charles Darwin:

    • Proposed the theory of biological evolution.

    • Human behavior is innate and adaptive.

  • Francis Galton and Eugenics:

    • Proposed a pseudo-scientific theory of eugenics, advocating selective breeding to improve the human race.

    • Premise: All social ills are inherited.

    • Goal: To "breed out" diseases, disabilities, and undesirable characteristics.

Approaches to Psychology

  • Biological Approach:

    • Nature: Focus on genetic, hormonal, and neuro-chemical explanations of behavior.

  • Psychoanalysis:

    • Nature: Innate drives of sex and aggression.

    • Nurture: Social upbringing during childhood.

  • Cognitive Psychology:

    • Nature: Innate mental structures (schemas, perception, memory).

    • Nurture: Environment constantly changes these structures.

  • Humanism:

    • Nature: Maslow emphasized basic physical needs.

    • Nurture: Society influences a person's self-concept.

  • Behaviorism:

    • Nurture: All behavior is learned from the environment through conditioning.

Epigenetics

  • Gene-Environment Interaction:

    • Genes \times Environment = Epigenetics

    • Specific environmental triggers (e.g., trauma, abuse) can "turn on" specific gene expressions.

    • Genetic predispositions (e.g., mathematical ability, alcoholism, violence) usually manifest due to environmental influences.

MAOA-L "Warrior Gene"

  • Influence on Violent Behavior:

    • Can genes make you violent?

  • Casspi et al. (2002) Study:

    • Prospective study following approximately 1,000 people in Dunedin, New Zealand, for 25 years.

    • Compared individuals with MAOA-H (high expression) and MAOA-L (low expression) genes.

    • Individuals with MAOA-L were more likely to commit violent crimes only if they experienced abuse in early childhood (epigenetics).

  • Meyer-Lindenburg (2008) Study:

    • Used fMRI to compare brain activity in participants with MAOA-L and MAOA-H.

    • Those with MAOA-L showed increased activity in the amygdala and decreased activity in the ventromedial prefrontal cortex (vmpfc) when viewing angry and fearful faces.

    • Similar results found by Raine (2008).

    • Significance: MAOA-L expression may lead to aggressive behavior because the vmpfc inhibits impulsive behavior, and the amygdala is associated with emotion and arousal.

Twin Studies

  • Methodology:

    • Uses correlational research to argue for a genetic origin of human behavior.

  • Heritability Questions:

    • What traits are inherited? Examples: intelligence, risk-taking behavior, depression, homosexuality, problem-solving skills.

  • Techniques:

    • Comparing Monozygotic (MZ) twins with Dyzygotic (DZ) twins to measure concordance rates.

      • MZ twins have identical DNA, so higher concordance rates suggest a genetic component.

    • Comparing MZ twins raised together vs. MZ twins raised apart.

      • This may provide better insight than comparing MZ and DZ twins raised together because it isolates environmental factors.

  • Adoption Studies:

    • Compare adopted children with their biological and adoptive mothers.

      • Higher concordance with the biological mother suggests a genetic influence.

    • Why adoption studies may be preferable to twin studies.

  • Strengths of Adoption Studies:

    • Allow researchers to isolate variables.

    • Matches between the adopted child and biological mother (e.g., IQ) despite no contact suggest a strong genetic influence.

  • Strengths of Twin Studies:

    • Produced data supporting the biological roots of disorders.

    • This helps psychologists stress prevention for vulnerable individuals.

    • High cross-cultural reliability of concordance levels.

  • Limitations of Adoption Studies:

    • Selective placement: Adopted children are often placed with families similar to their biological parents.

    • Adopted children and twins might not represent all children.

    • Being given up for adoption may affect the child’s behavior.

  • Limitations of Twin Studies:

    • MZ twins are rarely separated at birth and raised in completely different environments, which is necessary to substantiate claims.

    • MZ twins raised together share similar experiences, while DZ twins may not share the same experiences due to differences in appearance and temperament.

  • Prospective Studies:

    • Identify traits thought to be inherited and follow genetically vulnerable individuals over many years to see if they manifest the behavior (e.g., in schizophrenia studies).

    • Ethical concerns: May cause undue stress and iatrogenic effects in labeled individuals.

Nature vs Nurture Arguments

  • Develop 3-5 arguments (supported by peer-reviewed research) for the extent to which behavior is influenced more by genetics or environment, using the Myers textbook.

  • Include the name of the study/researcher that supports each argument (e.g., "Bobo Dolls" Study (Bandura 1961)).

  • Prepare 3-5 persuasive talking points from readings to support the argument that either genes or the environment have more influence over human behavior.