Interaction of Heredity and Environment

Heredity vs. Environment

  • Our behavior and mental processes are shaped by both heredity and the environment.
    • Heredity:
      • "Nature".
      • Refers to the genetic or predisposed characteristics that influence physical, behavioral, and mental traits.
        • Height.
        • Eye and hair color.
        • Sex.
        • Medical predispositions.
    • Environment:
      • "Nurture".
      • The external factors that a person experiences (in the womb and after birth).
        • Parenting.
        • Social Interaction.
        • Education.
        • Diet.
        • External Stimuli.

Interaction of Genes and Environment

  • Our genetic predispositions and our surrounding environments interact.
    • Environments can trigger gene activity.
    • Genetically influenced traits can evoke responses from others.
    • Example: Intelligence
      • Genetic factors play a role in determining a person’s cognitive ability.
      • Environmental factors such as education, socioeconomic status, and the quality of early childhood experiences can enhance or inhibit these genetic predispositions.
      • "Nurture works on what Nature endows".

Evolutionary Psychology

  • An approach to psychological inquiry that views human cognition (mental processes) and behavior through the lens of Darwinian Evolution.
    • Charles Darwin (1809-1882)
      • English naturalist.
      • Proposed the Theory of Evolution.
        • Involved a process of Natural Selection.
          • Forces such as competition for resources, disease, and climate tend to eliminate individuals who are less well-adapted to the environment.
          • Better-adapted individuals are more likely to survive and reproduce, changing the nature of the population over successive generations.
    • Evolutionary Psychologists examine the role of natural selection in the evolution of psychological mechanisms which allow adaptation to recurring behavioral problems relevant to the survival of the species.
      • Avoiding toxic foods.
      • Mate selection.
      • Altruism (concern for the welfare of others).
      • Social competition.

Eugenics

  • A social and political philosophy loosely based on Darwin’s Theory of Evolution and the Hereditary Genius Theory of Francis Galton.
    • Seeks to eradicate genetic defects and improve the genetic makeup of populations through selective human breeding.
      • Positive Eugenics: Promotes reproduction by individuals who have traits viewed as more desirable.
      • Negative Eugenics: Seeks to prevent reproduction by individuals who have traits deemed as undesirable.
    • The Eugenics position is groundless and scientifically naive.
    • Has been used historically to discriminate against various groups of people.
      • Example: Adolf Hitler’s persecution of Jews in Germany during World War II and promotion of the “Aryan Race”.

Research of Heredity vs. Environment

  • Research into the impact of genes on our behavior and mental processes comes in several forms.
    • Twin Studies
      • Identical (monozygotic): A single fertilized egg that has split in two.
      • Fraternal (dizygotic): Two separate eggs fertilized by two different sperm cells.
      • Compares sets of twins who were reared (raised) together and separately to see if genetics or the environment had a bigger effect on factors such as intelligence and personality.
    • Family Studies
      • Research conducted among siblings, parents, or children to assess evidence for genetic links for characteristics or outcomes, often related to health or disease.
    • Adoption Studies
      • Investigates the relationships among genetic and environmental factors in the development of personality, behavior, or disorders by comparing similarities of biological parent-child pairs with those of adoptive parent-child pairs.

Genetic Similarity in Twin Pairs

  • MZ-pairs (Monozygotic twins):
    • Both inherit 100% similar genes.
    • Always of the same sex.
  • DZ-pairs (Dizygotic twins):
    • Both inherit approximately 50% similar genes.
    • Same or different sex.

Criticisms of Evolutionary Psychology

  • Many psychologists take issue with elements of evolutionary psychology.
    • It starts with an effect and works backward to propose an explanation.
    • Unethical and immoral individuals have used it to discriminate against others.
      • Often used against women and non-caucasians.
    • Overlooks the effects of cultural expectations and socialization.