Nature and Nurture

Interesting morning on developmental considerations with Martha Farah which should resonate with most of my students.

Primarily the opening theme addressed the idea that development is both nature and nurture beginning with behavioral genetics studies in heritability (both adoption studies and twin studies but twin studies may be better for this type of work when you work with monozygotic twins). HOWEVER heritability estimates may be informative but they are NOT absolute, essential or immutable. Heritability studies cannot predict exactly how much is heritability and how much environment but only general trends and even then you need stable environments to factor for change in heritability.

Turkeimer et al. provided a strong analysis that often when environmental changes fluctuate widely it is hard to set up even categories of analysis much less comparative frameworks.  Such information helps researchers read large studies with care but not necessarily debunk all aspects of the study (see the discipleship commons twitter feed for access to articles on this subject)

Studies on the relationship between certain genes (for instance neurotransmitter-metabolizing enzyme monoamine oxidase or MAOA so that maltreated children with a genotype conferring high levels of MAOA expression were less likely to develop antisocial problems.) and even on environmental sensitivity to both stressful and nurturing environment.

Just a side note. Behavioral genetics seems to have trouble replicating and sustaining reliability but often have a lot of influence in drug therapy. My personal observation is that correlation work in population studies may be doomed. The deep suspicion of cultural construction compels some people to really want to deconstruct all studies at one level rather than understand that population studies are bounded but still helpful (funny that some of the same detractors will, however, validate anecdotal evidence). I may be wrong but this cultural suspicion really makes “nature” oriented studies very difficult in a number of settings, contributing to incommensurability between communities of academic discourse.

The case for environmental influence seems a bit more self evident due to the phenomenon of plasticity. Farah invoked the basic theme that neuronal connections depend on neuronal activity: i.e. “Neurons that fire together wire together” and can actually change macroscopic size and shape of brain! (See the London Taxi Driver study).

Overall plasticity reveals also critical environments where kittens, for instance, deprived certain pathways for perceiving cannot replicate them later. There are also “sensitive” periods where certain learning a second language is more adaptable (or where certain language issues like missing certain fricatives or plosives may occur).

A classic study revolves around ‘Genie’ was discovered in Arcadia, California, at the age of around 13. She had been locked away by her parents and had very little socialization. See http://www.integratedsociopsychology.net/genie.html. So you can partition questions of nature and nurture but not neatly or definitively. However a strong case can be made for both perspectives contributing to the conversation.

Farah continued with the overviews of developmental plasticity via synaptogenesis and pruning and the fact that adolescents do not have a fully developed “aspects” of PFC but with appropriate caveats.

The presentation closed with a discussion with ADHD… but I was too distracted to summarize.

About Dean G. Blevins

Dr. Dean G. Blevins currently serves as Professor of Practical Theology and Christian Discipleship at Nazarene Theological Seminary. An ordained elder, Dean has ministered in diverse settings and currently also serves at the USA Regional Education Coordinator for the Church of the Nazarene. A prolific author, Dr. Blevins recently co-wrote the textbook Discovering Discipleship and edits Didache: Faithful Teaching, a journal for Wesleyan Education.
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