mental
Nature/Nurture - Genes vs Environment
e.g. most people know siblings with entirely different personalities despite being raised in the same family environment.
Many if not most of the studies on this subject involve twins.
Identical vs Fraternal twins raised together and Identical twins raised apart.
Here a summary of some of the conclusions I've seen. This is not a rigorous rigorous search of the literature.
| Trait | Genetic (nature) | Environment (nuture) |
|---|---|---|
| Political Views | 30-40% | 70-60%% |
| Intelligence Test Scores * | 70-80% | 30-20% |
| Personalty | 56% | 44% |
See Jensen below
and Nature vs Nurture in Intelligence | wilderdom.com
According to Wikipedia,
"In a survey of scientists published 2014 by Edge, many respondents wrote that the dichotomy of nature versus nurture has outlived its usefulness, and should be retired. The reason is that in many fields of research, close feedback loops have been found in which "nature" and "nurture" influence one another constantly (as in self-domestication), while in other fields, the dividing line between an inherited and an acquired trait becomes unclear (as in the field of epigenetics[7] or in fetal development)."
I started thinking about this in 2012 when a Tea Party guy was invited to speak at a Christian group I belong to and spent most of the time making the claim that Charles Darwin was a racist who promoted eugenics and that "Darwinism" "led to" Nazism, the Holocaust, and other heinous historical events.
The truth is that in the late 19th century most people in England thought the Irish, Blacks and Highland Scots were an inferior form of homo sapiens. Darwin was basically silent on this issue.
Jensen IQ Paper:
In 1970 I audited a popular introduction to psychology course at Cal by Arthur Jensen who had just published an article in the Harvard Educational Review, "How Much Can We Boost IQ and Scholastic Achievement?".
He studied identical twins raised in different socioeconomic environments.
It concluded, among other things, that Head Start programs designed to boost African-American IQ scores had failed, and that this was likely never to be remedied, largely because, in Jensen's estimation, heritability of IQ was over 0.7 of the within-race IQ variability, and the 0.3 left over was due to non-shared environmental influences.
I had to go across picket lines to get to class, because the article was considered racist.
In a later article, Jensen argued that his claims had been misunderstood:
...nowhere have I "claimed" an "innate deficiency" of intelligence in blacks. My position on this question is clearly spelled out in my most recent book: "The plain fact is that at present there exists no scientifically satisfactory explanation for the differences between the IQ distributions in the black and white populations. The only genuine consensus among well-informed scientists on this topic is that the cause of the difference remains an open question."As I recall he argued in our class the IQ tests are a measure of the ability to do well in a traditional academic environment not raw intelligence.
See Nature vs Nurture in Intelligence | wilderdom.com
In
The Bell Curve: Intelligence and Class Structure in American Life (New York: Free Press, 1994) a bestseller funded by the conservative American Enterprise Institute (AEI) a psychologist, Richard J. Herrnstein, and conservative policy advocate, Charles Murray try to prove that both the class structure and the racial divide in the United States result from genetically determined differences in intelligence and ability.
It was also quite controversial and prompted another book
Inequality by Design: Cracking the Bell Curve Myth where the authors state,
"The Bell Curve made two key claims. It said that social class no longer shapes Americans' life chances, and that the talents reflected in test scores and educational credentials are largely bred not taught. Both of these claims are wrong."Herrnstein and Murray use the Armed Forces Qualifying Test (AFQT) as the measure of IQ. This test has questions which would bias results towards those educated in upscale suburban schools. They also treat parents income and educations equally in determining socioeconomic background, which also biases the results.
A NY Times article "Genetic Basis for Crime: A New Look", June 19, 2011, author P. Cohen says, "It was less than 20 years ago that the National Institutes of Health abruptly withdrew funds for a conference on genetics and crime after outraged complaints that the idea smacked of eugenics."
Today a small cadre of experts is exploring how genes might heighten the risk of committing a crime and whether such a trait can be inherited.
"Researchers estimate that at least 100 studies have shown that genes play a role in crimes." However, "everyone in the field agrees there is no "crime gene." What most researchers are looking for are inherited traits that are linked to aggression and antisocial behaviors, which may in turn lead to violent crime. Don't expect anyone to discover how someone's DNA might identify the next Bernard L. Madoff."
Terrie E. Moffitt, a behavioral scientist at Duke University, said. "Today the most compelling modern theories of crime and violence weave social and biological themes together."
In findings from a long-term study of 1,000 babies born in 1972 in a New Zealand town, Ms. Moffitt and her colleagues recently reported that the less self-control a child displayed at 3 years of age, the more likely he or she was to commit a crime more than 30 years later. Forty-three percent of the children who scored in the lowest fifth on self-control were later convicted of a crime, she said, versus 13 percent of those who scored in the highest fifth.
"Steven Pinker, a professor of psychology at Harvard whose forthcoming book, "The Better Angels of Our Nature," argues that humans have become less violent over the millenniums, suggests that the way to think about genetics and crime is to start with human nature and then look at what causes the switch for a particular trait to be flipped on or off."
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