Heredity and Environment

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Heredity and Environment
Michael Hoerger
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Introduction

• Long-standing debate nature vs. nurture
  (heredity vs. environment, genetic diathesis vs.
  stress)
• Opinions fluctuate over time (multicontextual)
• What is the current zeitgeist?
• Alcoholism, ADHD, schizophrenia, IQ, personality
  traits, athletic and music ability

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Heritability

• Definition extent that observed differences on a
  trait or behavior are due to genes
• Psychologists and behavior genetics researchers
  attempt to estimate heritability using the
  heritability coefficient, h2

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h2

• Ranges from 0 to 1
• Higher h2 genes estimated to account for more
  variation in a trait (genes are more important)
• Compares MZ twins to DZ twins, using complex
  calculations
• Only a very rough estimate, depends on the
  particular sample, time period, context

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Runs in families Heritable?

• Many traits, such as leadership, political
  skills, ideology, and moral strength, run in
  families. Look at the Bush family, the Kennedys,
  the Roosevelts. We are the product of good genes.

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Sorry, Mr. President

• If a trait runs in families, it could be due to
• Genes
• Social learning (modeling)
• Operant conditioning (rewards)
• Sociocultural variables (SES)
• Chance

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Heritable Unchangeable?

• Once a schizophrenic always a schizophrenic
• Alcoholism is a disease you must battle your
  entire life

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Sorry, Dr. Meehl

• Some heritable traits are difficult to change
• Others change across generations (height)
• Some highly heritable conditions are easily
  modified
• Vision
• Mental retardation due to Phenylketonuria (PKU)

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Heritable Drug Treatment?

• If a condition is heritable, treat it with
  drugs
• If a condition responds to drugs, it is probably
  heritable.

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Sorry, Dr. Berger

• Heritable conditions may respond just fine to
  social and behavioral interventions
• Anxiety treatments
• Bedwetting
• Heritability is not closely linked to the type of
  treatment that works

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h2 is a Constant?

• IQ, personality traits, criminality, and
  psychological disorders are all highly heritable,
  with h2 gt .50!

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Sorry, Mr. Murray

• h2 is only an estimate, depending on the
• Sample studied (e.g. Americans)
• Historical context (time)
• Location studied (place)
• h2 varies substantially by group, time, and place
• Schizophrenia, depression, liberalism,
  conscientiousness

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Schizo-gene?

• A new study has finally found the gene for
  schizophrenia!

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Sorry, News Media

• There is no schizo-gene, or depression gene, or
  leadership gene
• Most psychological traits are complex, depending
  on
• Multiple genes interacting
• Numerous environmental effects

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In Summary

• Remember the Gould video!
• Dangerous harmful to label problems as
  heritable and unchangeable when they are not
• Currently fashionable to make this mistake
• Misunderstand heritability, ignore importance of
  environment

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• Michael Hoerger
• To cite this lecture
• Hoerger, M. (2007, January 17). Heredity and
  Environment. Presented at a PSY 220 lecture at
  Central Michigan University.