Soci326-002 – Evolutionary Sociology

Module 6 – Biology of Behavior – Human Diversity I – Discussion Topics – 4 Oct 2005

Today's readings cover

• Pinker.  The Blank Slate.  Chapter 19 -- Children (Pp. 372--399)
• Rowe.  Limits of Family Influence.
  • Introduction & Chapter 1 - The Primacy of Child Rearing in Socialization Theory - Pp. 1-28
  • Chapter 2 - Separating nature and Nurture - Pp. 29-56
  • Chapter 3 - As the Twig is Bent?: Families and Personality - Pp. 57-96

This is the first module concerned with the biological basis of human differences, as distinct from general features of human nature (i.e., our "common genetic heritage" in Lenski's terminology).

Here are some topics for discussion.

1.  Pinker (Pp. 372--381) discusses Turkheimer's (2000) "three laws" of behavior genetics, which are

1. "All human behavioral traits are heritable." (As Pinker later comments (p. 375) this is "[a] bit of an exaggeration, but not by much".)
2. "The effect of being raised in the same family is smaller than the effect of the genes."
3. "A substantial portion of the variation in complex human behavioral traits is not accounted for by the effects of genes or families."

Based on Pinker (Chapter 19) and Rowe (Introduction, Chapters 1, 2, and 3), let's discuss the following issues:

What kinds of empirical findings constitute the basis of Turkheimer's 3 laws, and how (or how not) compelling are these findings, in the following domains of human behavior:

1. personality (particularly the "big 5" OCEAN personality traits of intellectual Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism (v. emotional stability)
2. psychopathology (including schizophrenia, mood disorders, externalizing disorders, internalizing disorders)
3. social attitudes (authoritarianism, see social attitude items in Rowe Table 3.8, p. 85)
4. religious affiliation (distinguishing between religious affiliation and religiosity; what other traits are largely related to the family common environment?)

2.  The findings of behavior genetics are based on a number of study designs, which have specific advantages and drawbacks.  In general what are the pros and cons of the following designs:

1. separated-twins design with r_MZA = h² (MZA means monozygotic twins raised apart)
2. nontwin adoption designs with r_URT = c² contrasted with r_FST = c² + (1/2)h² (URT means unrelated children raised together, as in the case of adoption)
3. classical twin designs with 2(r_MZT - r_DZT) = h² and 2r_DZ - r_MZ = c²
4. model-fitting designs (see Figure 2.2 p. 50)
5. association and linkage analysis (molecular genetic methods)

3.  Much of sociological research in life-course outcomes (such as delinquency, drug use, high school graduation, educational achievement, socio-economic attainment) looks at associations between characteristics of the family of origin or aspects of parenting style and outcomes, concluding that some characteristics of childhood experience (such as having parents who read to the child) have a causal influence on life-course outcomes.  What's problematic with that type of research in view of the accumulated findings of behavior genetics?

4.  What are the social, moral, political, etc., implications of the findings that the rearing environment (within a human range, excluding very abusive or neglectful environments) may not matter much in explaining late adolescent and adult outcomes?  Is this a piece of knowledge that should be suppressed, on the ground that if parents think it does  not matter they will stop caring for their children?

Last modified 4 Oct 2005