Steven Crane Compiled Section Handouts. Human Behavioral Biology 2012

Particularly in the splitting of cells, brownian motion (unpredictable, probabilistic movement of atoms and molecules) will not cause equal 50-50 splits of all the TFs and hormones and other cytoplasmic things.

Key examples - know the details, their significance, their criticisms. What do they illustrate? Why are they included?

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  Benbo and Stanley's gender differences in math from the CTY kids
  

  • At first concluded it was a reliable (genetic) sex difference that males outperformed females at math because their mathematics environments were "identical"

  • But the different sexes are treated differently. And upon retesting 30 years later the differences are small to disappearing (too short a time for strong genetic shifts). AND looking across countries, the smaller the gender gap in social/political/economic terms, the smaller the gender gap in mathematical performance.

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    But the difference does seem to hold true that males outperform females on average and not very hugely on spatial tasks. And females also seem to consistently outperform males on average and not very hugely on verbal tasks.
    
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  Kety's schizophrenia adoption studies
  
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  The Dutch Hunger Winter
  
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  Phenylketonuria and gene/environment interactions
  
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  Depression and gene/environment interactions
  
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  MAO variation and aggressive behavior gene/environment interactions
  

Take-Home Points

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  Environment does not begin at birth; it begins at conception. And supposedly subtle prenatal effects can be anything but subtle.
  
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  Most interesting human behavior is not about deterministic single genes. Many genes are involved in almost any behavior, plus they're all interacting with the environment.
  
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  It is meaningless to talk about what a gene does, only what it does in a particular environment. The more you know about genetics, prenatal environment, early childhood experiences, societal context, stressors, etc., the more predictive you can actually be about important outcomes (like risk for depression).
  
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  But genes are of course important to behavior. Gene X Environment = Behavior just as Width X Length = Area
  

Example exam questions

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  Why do traditional scientific approaches under-estimate the role of environment in determining a behavior?
  
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  Define heritability in one sentence (2 points)
  
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  Seymour Kety examined incidence rates of schizophrenia in a large number of cases of early adoption in Denmark in the 1960's. A simplified summary of the outcomes is shown below.
  

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  Percentages in the table above represent the incidence rate of schizophrenia for each context (for example, 1% of all the individuals with NON-schizophrenic biological parents and NONschizophrenic adoptive parents have schizophrenia).
  

Briefly describe how analyzing these groups might lead to a dissociation between genetics and
environment. (2pts)
“Environment does not begin at birth.”

1. 
   Give three examples of this principle from class. (6 pt) Prenatal stimulation and learning mom's voice Prenatal stress and later stress reactivity
   

Prenatal malnutrition and later thrifty nutrient phenotype Drug addiction can occur in the womb