Friday, May 22, 2015
The wide-ranging influence of genetics
The Left long denied the influence of genetics but now simply ignore it. The study below is therefore powerful evidence of just how wrong they are. Hans Eysenck, a considerable student of genetics, once said to me, "It's ALL genetic". He was of course making a conversational statement to a colleague rather than a precise scientific one but the present study does confirm one sense of what he said: ALL traits have a substantial genetic component. And the writer below makes the correct and important point that the 50/50 split observed is only an average and that the genetic contribution varies from trait to trait. So the findings do not overturn the usual finding that IQ is about two thirds genetic
It's a question that dogged scientists for close to a century and Queensland researchers say they have the answer. When it comes to health, in the age-old battle of nature versus nurture… It's a draw.
University of Queensland research fellow Dr Beben Benyamin worked with scholars at the VU University of Amsterdam to review almost every twin study completed globally in the past 50 years.
After analysing studies of more than 14.5 million twin pairs across 17,804 traits from 2748 publications, they found variation for human traits and diseases was 49 per cent genetic (nature), and 51 per cent due to environmental factors (nurture).
The Queensland Brain Institute researcher said the draw was expected but he was pleased to be able to put a number on the variation and surprised by how similar an influence each aspect had.
"Most of the reviews have been for specific traits, like people are interested in studying one particular disease and review all the twin studies for one disease," he said. "But this is I think is the first one to review everything about all disease and all twin studies that are available at the moment."
The influence of nature and nurture is actually a complex interplay rather than a simple either/or and is far from equal across all traits and diseases.
The risk for bipolar disorder was about 70 per cent due to genetics and 30 per cent due to environmental factors, Dr Benyamin found.
Posted by jonjayray at 11:04 AM
Wednesday, May 20, 2015
Black Brain, White Brain?
There came out recently a book called Black Brain, White Brain -- by Gavin Evans. It seems to have got some acclaim so I thought I might say a bit about it. That task seems to be facilitated by an article by Evans under the same heading which appeared just over a month ago. The article seems to summarize the main points of the book and thus spares me the time of reading the book. But if there are things in the book which undermine any of the things I day below, I would be delighted to hear of it.
The main point of the book seems to be an accusation that it is racist to discuss the black/white IQ gap. And like all other efforts in that direction that I know of it does a lot of huffing and puffing and declaring things obvious rather than providing proof of them. The abusive and intemperate writing by Evans may be judged by his reference to "racist science that has been spewing out of the computers". Do computers spew? His use of abusive language like that is certainly a strong indication that he has a weak case that he is trying to cover up. "fester" and "dangerous" are other emotive words he uses. Abuse in lieu of facts is a very familiar Leftist modus operandi. And a few of Evans's assertions do seem to be simply wrong.
And in the best Leftist style, his writing is almost entirely an appeal to authority. Quite illogically, he thinks that because other people have declared something wrong then it must be wrong. That many people have declared genetically-oriented treatments of the black/white IQ gap to be wrong and mistaken proves nothing at all. It simply shows that most academics are Leftist. For Evans to have written in any sort of scholarly way, he would have to list the main points where the genetic writers were found to be in error. He does not do that.
He seems to think that he has made a great point by saying that no one gene for IQ has been discovered. So what? IQ researchers have for decades accepted with perfect calm that IQ is polygenetic. Whether one gene or many is behind a difference may make research more or less difficult but it does not take away from the fact that the difference is genetic. And the genes that do contribute to IQ differences are being discovered all the time. I must make a list of the studies concerned some time. I have noted quite a few on this blog.
He then goes on to claim that intelligence has not evolved for 100,000 years. That completely ignores the work of Bruce Lahn, who showed a major evolutionary change in brain size about 5,000 years ago, a change which coincided with the birth of civilization and which is almost unknown in Africa. Pesky!
Another claim by Evans: "Other studies have also shown that the IQs of children adopted into middle class homes rise significantly and that these increases can persist into adulthood". He is right about the first part but wrong about the second part. Manipulations of the environment can improve IQ scores in childhood and even into the teens but by about age 30, all those improvements are lost. By age 30 most environmental influences have washed out and the genetic endowment comes to the fore.
And then Evans gets on to the good ol' Flynn effect. So much has been written about that that I hesitate to write any more but in summary, the Flynn effect seems to be an artifact of increasing years of schooling and the test sophistication that engenders. On important IQ subtests -- such as vocabulary -- where being test-wise does not help -- there has been very little movement in scores. And in some advanced countries -- such as Nederland -- the rise has petered out, as one would expect if it was just a one-time artifact that had approached an asymptote (maximum value).
Finally, I am amazed by his assertion that "black American IQs are rising at a faster rate than those of white Americans". I know of no evidence for that. In fact, on some indices, the black/white gap is increasing. So I guess I will have to "fester" away in my conclusion that there are real and inborn differences between the average IQs of blacks and whites.
And let's not have the old nonsense that IQ tests measure something limited and mysterious. They measure general problem-solving ability, which is why researchers tend to use the term 'g' instead of 'IQ'.
And I may note that my view of IQ is no longer academically marginalized stuff at all. I don't quite know whether to be pleased or disappointed but it seems that mainstream psychology is catching up with what psychometricians such as myself have been saying for years: That IQ is highly general, highly central, highly hereditary and of overwhelming importance in determining people's life-chances. Not so long ago any claim to that effect would be very marginal within psychology and would expose anyone making it to all sorts of nasty accusations.
But you can now read it all not in some obscure academic journal or some Rightist source but in a 2004 issue (vol. 86 no. 1) of the American Psychological Association's most widely-circulated journal -- the Journal of Personality and Social Psychology.
Article after article there sets out the importance of IQ. And for social psychologists to be taking an interest in such evidence is really amazing. Psychometricians have known all that stuff for years. It is the social psychologists who have been most resistant to such ideas. I guess that even an organization as Leftist as the American Psychological Association has to come to terms with the evidence eventually.
And note that the APA conceded some time ago that "African American IQ scores have long averaged about 15 points below those of Whites". 15 points is one standard deviation, which is a huge difference -- accounting for 34% of the distribution. So it looks like I've got a lot of company in my "festering", as Evans calls it. Evans is fighting a lost battle.
Posted by jonjayray at 11:09 AM