Improve Your IQ: Practical Exercises & Tips from John G.

[Aquamarine]

I find this discussion more and more uninteresting. You continue to ignore peer-reviewed studies contradicting the theories of Jensen and Rushton.

In general, I only state that many questions are unresolved. But you make many strong claims regarding these issues, claiming proved answers. As such, it is up to you to provide the evidence in the form of peer-reviewed studies.

The Jensen study I referred to was the study you referred to earlier in this thread. I should not have said the Jensen study but the twin study used by Jensen as evidence in your quote.

Regarding 1 and 3, do Jensen claim to explain more than only the US variance right now? If so, please provide which peer-reviewed studies he uses as evidence.

Regarding 2, you fail to provide evidence that the gaps will not dwindle in the future. And I certainly agree that "the extent to which the level of g per se has been rising (or falling) over the past few decades remains problematic."

Regarding 4, my statement need no studies, saying only that there may or may not be a relationship. But you seem to claim something stronger than that, that there is no relationship. Which peer-reviewed studies support your position?

Again regarding "macro", a wealthy family/society environment can provide better "micro" factors which will affect intelligence. For example iodine supplementation in rich countries with good health-care. Please provide the peer-reviewed studies claiming otherwise for the world as whole, not only the US.

Finally regarding your statement "Evidence (published in peer reviewed journals) from the past few years has shown that the Flynn effect is due entirely to increases in specificity and not g. There is zero gain in g from the Flynn effect.":

Several studies have addressed the issue whether differential gains on intelligence subtests are positively correlated with the g loadings of these subtests (Colom et al., 2001; Flynn, 1999a; Jensen, 1998; Must et al., 2003; Rushton, 1999, 2000). This issue concerns the question whether between-cohort differences are attributable to the hypothetical construct g. As such, these studies address the same question as we do here. However, we do not limit ourselves to g and employ MGCFA, rather than the method of correlated vectors (i.e., correlating differences in means on a subtest and the subtest’s loading on common factor, interpreted as g). Using the method of correlated vectors, Jensen (pp. 320–321), Rushton, and Must et al. found low or negative correlations and conclude that the Flynn effect is not due to increases in g. However, Flynn (1999a, 1999b, 1999c, 2000a), in a critique of Rushton’s conclusions concerning Black–White (B–W) differences, obtained contradictory results. In addition, Colom et al. (2001) report high positive correlations using the standardization data of the Spanish Differential Aptitude Test (DAT). Thus, it remains unclear whether the Flynn effect is due to increases in g. It may be argued that the contradictory findings are the result of differences in the tests’ emphases on crystallized or fluid intelligence (Colom & Garcı´a-Lo´ pez, 2003; Colom et al., 2001). However, of more immediate concern is the method of correlated vectors. This method has been criticized extensively by Dolan (2000) and Dolan and Hamaker (2001). One problem is that the correlation, which forms the crux of this method (i.e., the correlation between the differences in means and the loadings on what is interpreted as the g factor), may assume quite large values, even when g is not the major source of between-group differences (Dolan & Lubke, 2001; Lubke, Dolan, & Kelderman, 2001). Indeed, this correlation may assume values that are interpreted in support of the importance of g, while in fact, MGCFA indicates that factorial invariance is not tenable (Dolan, Roorda, & Wicherts, 2004).

http://users.fmg.uva.nl/jwicherts/wicherts2004.pdf (my emphasis)

 

[hitssquad]

Nutrition vs race in group IQ disparities

there are many studies showing the importance of deficiency in vitamins and minerals in decreasing iq.

Richard Lynn authored many of those studies. Lynn and Vanhanen spend many pages of Chapter 10 of discussing the impact of nutrition on IQ and concluding that improved nutrition should reduce the IQ gap between poor, low-IQ nations and rich, high-IQ nations:
http://groups-beta.google.com/group/sci.econ/browse_frm/thread/f4e99b413091c04/0b712bb9c75d904f?q=author:ginger3nut@yahoo.com+lynn&_done=%2Fgroups%3Fhl%3Den%26q%3Dauthor:ginger3nut@yahoo.com+lynn%26&_doneTitle=Back+to+Search&&d#0b712bb9c75d904f

• (pp 186-188):
  <begin quote>
  We are by no means alone in concluding that the quality of nutrition
  is a major environmental determinant of intelligence. This conclusion
  has been reached by a number of researchers. For instance, "Inadequate
  levels of vitamins and minerals in the blood stream reduce a child's
  IQ below the optimum level (Eysenck and Schoenthaler, 1997, p. 387);
  "The evidence suggests that nutrition and intelligence are linked in
  that children with better diets, in terms of both quantity and quality
  of food, show superior performance on developmental and cognitive
  tests than children who are less well fed" (Sigman and Whaley, 1998,
  p. 172). The implication of this conclusion is that measures to
  improve the quality of nutrition in poor countries would be one way to
  increase the intelligence levels of their populations.

However, if the white-black IQ gap in the United States were entirely non-genetic, high-SES (wealthy) black families might be expected to bear higher-IQ offspring than would low-SES (poor) white families. In fact, it has been found that children from high-SES Black families have lower IQs than do children from low-SES White familes.

• One would expect, on purely environmental grounds, that the mean IQ difference between black and white children should decrease at each successively higher level of the parental socioeconomic status (i.e., education, occupational level, income, cultural advantages, and the like). It could hardly be argued that environmental advantages are not greater at higher levels of SES, in both the black and the white populations. Yet, as seen in Figure 11.2, the black and white group means actually diverge with increasing SES, although IQ increases with SES for both blacks and whites. The specific form of this increasing divergence of the white and black groups is also of some theoretical interest: the black means show a significantly lower rate of increase in IQ as a function of SES than do the white means.

(Arthur Jensen. The g Factor. p469.)


Also:

• A large-scale study [58] specifically addressed to the effect of early versus late age of adoption on children's later IQ did find that infants who were adopted before one year of age had significantly higher IQs at age four years than did children adopted after one year of age, but this difference disappeared when the children were retested at school age.

(Arthur Jensen. The g Factor. p477.)

 

[hitssquad]

Generality of Jensen's finding of a racial basis to the US black-white IQ gap

do Jensen claim to explain more than only the US variance right now?

US blacks are largely, though in general not completely, descended from sub-Saharan African blacks. If we see a white-black difference in the United States in terms of anyone given phenotypic variable, and that difference is partially genetic, a similar or larger difference might be found between blacks and whites in sub-Saharan Africa. Jensen terms this aspect of his US finding generality.

• Generality. The W-B difference in IQ is not confined to the United States, but is quite general and in the same direction, though of varying size, in every country in which representative samples of the white and black populations have been tested. The largest differences have been found in sub-Saharan Africa, averaging about 1.75σ in 11 studies. [7a,b] The largest difference between white and African groups (equated for schooling) is found on the Raven matrices (a nonverbal test of reasoning). In one large study the mean difference averaged about 2.0σ for Africans with no apparent European or Asian (East Indian) ancestry and about 1.1σ for Africans of mixed ancestry. [8] The East Indians in Africa averaged about 0.5σ below Europeans with the same years of schooling.
  
  Studies in Britain have found that the mean IQ difference between the white and the West Indian (mainly African ancestry with some [unknown] degree of Caucasian admixture) populations is about the same as the W-B difference in the United States. [9] Recent immigrant East Indian children score, upon arrival in Britain, about as far below the British mean as do the West Indians, but, unlike the West Indians, the East Indians, after spending four years in British schools, score at about the same level as the indigenous white Britishers. A longitudinal study [10] of this phenomenon concluded, "The most striking result of the longitudinal IQ test results was the declining scores of the West Indians and the rising scores of the Indian children, in comparison to the non-minority children in the same schools. It appeared that the Indian children were acquiring the reasoning skills expected of children in the 8-12-year period, while the West Indians were not keeping pace in reasoning skills with most British children" (p. 40).
  
  
  • 7. (a) Lynn, 1991a; (b) Zindi, 1994.
    8. Owen, 1992.
    9. Mackintosh & Mascie-Taylor, 1985.
    10. Scarr, Caparulo, Ferdman, Tower, & Caplan, 1983.
    
    
    • Lynn R. ( 1991a). "Race differences in intelligence: A global perspective". Mankind Quarterly, 31 , 254-296.
      
    • Mackintosh N. J. & Mascie-Taylor C. G. N. (1985). "The IQ question". Annex D to Education for all. (Chairman, Lord Swann) Report of the Committee of Inquiry into the Education of Children from Ethnic Minority Groups. London: Her Majesty's Stationery Office.
      
    • Owen K. (1992). "The suitability of Raven Standard Progressive Matrices for various groups in South Africa". Personality and Individual Differences, 13, 149-159.
      
    • Scarr S., Caparulo B. K., Ferdman B. M., Tower R. B. & Caplan J. (1983). "Developmental status and school achievements of minority and non-minority children from birth to 18 years in a British Midlands town". British Journal of Developmental Psychology, 1, 31-48.
      
    • Zindi F. (1994). "Differences in psychometric performance". The Psychologist, 7, 549-552.

(Arthur Jensen.The g Factor. pp359-360, 403-404, 619, 620, 623, 627, 634.)

 

[Mandrake]

I find this discussion more and more uninteresting. You continue to ignore peer-reviewed studies contradicting the theories of Jensen and Rushton.

Wrong. I read the paper you referenced when it was published and have met the author.

While accusing me of ignoring material, you elected to edit out the following:

The Flynn effect comprises elements that you apparently do not wish to take into consideration or which you have not encountered. For example, data showing secular gains is usually the result of improved IQ scores below the mean, not above it. This causes the mean to shift.

Among the curiosities of the Flynn Effect: “When the g loaded test is composed largely of nonscholastic items (matrices, figure analogies), the raw scores show a secular increase; when an equally g loaded test is composed of scholastic items (reading comprehension, math) the raw scores show a secular decrease. Obviously, the sure level of g cannot be changing in opposite directions at the same time. The difference in vehicles must account for the discrepancy. So, the extent to which the level of g per se has been rising (or falling) over the past few decades remains problematic.”
[The _g_ Factor, P. 322]

Please explain your comment in light of this observation.

Why did you "ignore" that material and why did you not offer the explanation that I requested?

In general, I only state that many questions are unresolved. But you make many strong claims regarding these issues, claiming proved answers. As such, it is up to you to provide the evidence in the form of peer-reviewed studies.

The evidence:
Item 1 There is both a positive and a negative effect that can be demonstrated from equally g-loaded test items. This indicates that the Lynn-Flynn effect is an artifact.

Item 2 Inspection time data show no secular gain or loss. IT is strongly related to g. If g were increasing, we should see a decrease in IT. That has not happened. See Nettelbeck and Wilson, Intelligence Volume 32, Issue 1, January-February 2004, Pages 85-93.

Item 3 Rushton has presented a robust argument that there is no g-loading to the changes in IQ scores: Rushton, J. P. (1999) Secular gains in IQ not related to the g factor and inbreeding depression unlike Black-White differences: A reply to Flynn. Personality and Individual Differences, 26: 381-389. I suggest reading this completely and carefully.

Item 4 It is most likely that intelligence is declining in the US:
New evidence of dysgenic fertility for intelligence in the United States [Richard Lynn, and Marian Van Court, Intelligence Volume 32, Issue 2, March-April 2004, Pages 193-201] Here are a few comments from that paper: The results of the present study confirm and extend the second set of studies in that they show that the association between intelligence and fertility has been consistently negative for all birth cohorts from 1900–1919 up to 1970–1979. ... our results show that there is no tendency for the childless to have low IQs or for those with low IQs to be childless. ... In the present data, the decline of genotypic intelligence for the 1940–1949 birth cohort is calculated at .9 IQ points per generation for the overall population, and .75 IQ points per generation for the White population. Retherford and Sewell calculated a genotypic decline of .81 IQ points from their data set consisting almost entirely of Whites and born around the same time.

Item 5 The best study of the effect, under controlled conditions, showed no g gain:
"The secular rise in IQs: In Estonia, the Flynn effect is not a Jensen effect"
Aasa Must and Vilve Raudik, Intelligence, Volume 31, Issue 5 , September-October 2003, Pages 461-471
Our study found that the secular changes in Estonia over the last 60 years were not on g, the general factor of intelligence. As such, they were not Jensen effects. Flynn, 1999 and Flynn, 2000 has suggested that failures to find secular gains are due to the use of tests of "crystallized" intelligence because secular gains occur mostly in "fluid" intelligence. However, we agree with Jensen (1998, pp. 122–125) that the g factor makes the distinction between fluid and crystallized intelligence largely superfluous.

The Jensen study I referred to was the study you referred to earlier in this thread. I should not have said the Jensen study but the twin study used by Jensen as evidence in your quote.

Yes, you were not familiar with the source, nor the fact that Jensen has not been a twin researcher.

Regarding 1 and 3, do Jensen claim to explain more than only the US variance right now? If so, please provide which peer-reviewed studies he uses as evidence.

Let me repeat what you wrote: 1. The Jensen study you referred to only applies to US variance. Not to US mean, not to variance earlier in US history and not to mean and variance in other countries.
I do not pretend to understand what you have written. Can you explain it? It remains unclear as to which studies have confused you, or why you are concerned over the US population. Both twin and adoption studies have been conducted in the US and various European countries. Jensen has reported most of them in his last book. If you have a point to make, please state it.

Regarding 2, you fail to provide evidence that the gaps will not dwindle in the future.

What kind of evidence do you think would be available today and would prove something in the future with respect to your speculation? I can't imagine why anyone would bother to respond to speculation. There was no point in your comment and it was not related to any study or evidence.

Regarding 4, my statement need no studies, saying only that there may or may not be a relationship. But you seem to claim something stronger than that, that there is no relationship. Which peer-reviewed studies support your position?

Your comment simply showed that you were still confused. I replied: Who has excluded IQ in childhood from what? IQ can be measured in children and it is reasonably predictive of adult IQ. The issue that you apparently do not understand has to do with the variance in IQ due to shared environment. Why don't you take time to disabuse yourself of your misconceptions?

Where does my comment say something about "no relationship?" Relationship of what to what?

Again regarding "macro", a wealthy family/society environment can provide better "micro" factors which will affect intelligence. For example iodine supplementation in rich countries with good health-care. Please provide the peer-reviewed studies claiming otherwise for the world as whole, not only the US.

You remain unable to understand the difference between micro and macro. The macro environment consists of social interactions, not chemical ones. Your iodine mantra is evidence of your inability to admit that you are wrong and that you do not understand the terms. I have suggested that you remedy this by learning. In this case, the starting point is Jensen, A. R. (1998). The g factor: The science of mental ability. Westport, CT: Praeger.

Finally regarding your statement "Evidence (published in peer reviewed journals) from the past few years has shown that the Flynn effect is due entirely to increases in specificity and not g. There is zero gain in g from the Flynn effect.":
Quote:
http://users.fmg.uva.nl/jwicherts/wicherts2004.pdf (my emphasis)

I fail to see anything significant in the material you reported. As I previously mentioned, I read it when it was published. I personally have no confidence in the expertise of Jelte Wicherts. He is a very likable and polite young man, who does not project any air of expertise. I listened to his presentation on December 2 and was underwhelmed. His was the ONLY paper to be addressed directly by another speaker as being inappropriate. In any field of study you can find a few people who are outliers. Some of them may be outliers because they are highly expert and correct, while the rest are wrong. When that is the case, those people are usually able to support their differences soundly. Jelte has not done that.

It is important for anyone who hopes to understand a discipline to be able to weigh and take into account the total body of knowledge. I have presented you with five significant items that independently support what I have written about the Lynn-Flynn effect. When you take the time to understand these five items, I am confident that you will understand the reality of what is happening.

 

[Tasthius]

Interesting discussion on IQ as always. Though I think Mandrake got the best of this one, I wanted to point out one error he/she made. He/she stated that IQ tests are only good for "one usage" in a person's life. This isn't true. Statistical studies show that a person's IQ over life (except perhaps at very advanced ages) will vary hardly at all even if they take any given test numerous times (assuming no sort of test compromise occured). I think it has even been shown that when people "train" for certain types of questions, that even then, their scores increase very little. This is known as "test-retest reliability" and is one of the marks of a good psychometric instrument. Such a proven test should have this characteristic along with the others mentioned here:

http://www.wilderdom.com/personality/L3-2EssentialsGoodPsychologicalTest.html

 

[Achterberg]

Mandrake,

I find it very inappropriate to publicly attack Jelte Wicherts' expertise in a discussion related to a small segment of a paper written by him and several very well known scholars such as Dorret Boomsma and Conor Dolan (both leading behavioural geneticist!).

Please stick to the content of the Flynn Effect paper of Wicherts et al.: Its results indicate that the Flynn Effect is not related to g! There is no need to attack someone personally, certainly not by referring to a vague statement about a talk you have once attended.

C. Achterberg

 

[Mandrake]

Interesting discussion on IQ as always. Though I think Mandrake got the best of this one, I wanted to point out one error he/she made. He/she stated that IQ tests are only good for "one usage" in a person's life. This isn't true.

It would be helpful if you quoted my exact words. I don't recall which message contained the comment, but I believe I did not state that this was a universal situation, nor did I say that repeated use of a test was necessarily going to give higher specificity. I believe I commented that some IQ tests specify that the test be used only once to test a particular individual. That is a direction from the supplier of the test.

 

[Aquamarine]

hitssquad
1. First, there are several reasons to believe that those taken as slaves to the US or West Indies (and then many as emigrants to Europe) may have a different and lower average IQ than in Africa.They were only taken from certain costal regions, many from Nigeria. There can be very large differences in measured iq even between close neighbors, like the difference between catholics and protestants in Ireland. Also, there are large iq differences in the same group. Probably, the easiest slaves to capture come from low iq areas and in those areas from those with the lowest iq. Furthermore, it is known that animals doing simple tasks in agriculture have much lower intelligence than those in freedom. So iq may have declined further in the US during the slave period.

2. One cannot easily measure the iq gap between "races" for the world as whole. Studies done in Africa ignore that many blacks will have lowered iq due to for example inadequate nutrition. Studies done in the US and Europe ignore at least that the blacks there are not a random sample from Africa, as stated above.

3. The black-white gap in England is much less than in the US, showing that the US results cannot be applied even to another western country with many blacks descended from slaves.
http://www.gnxp.com/MT2/archives/001047.html

Therefore, even assuming the US B-W gap is completely genetic, this says little about the gap and its genetic component, if any, in the rest of the world.

Mandrake
First, I did not ignore you request for explanation. I stated that I agreed with "So, the extent to which the level of g per se has been rising (or falling) over the past few decades remains problematic." This is not incompatible with "The Flynn effect may well have started earlier for the more affluent subgroups, both in and between nations. A reasonably possibility is therefore that it will also disappear for this groups first. Thus the gap in IQ may dwindle or disappear in the future." I only stated that it may, not that it must.

Still no answers:

1. The iq studies trying to measure the size of the genetic vs non-genetic factors only applies to the US (and maybe some European countries) variance. Not to US mean, not to variance earlier in US history and not to mean and variance in other countries. Se also my response to hitssquad.

2. There is no reason to exclude iq in childhood and adolescence automatically without evidence. Most human learning take place in those periods, so even only a temporary increase, for example due to intervention by society, may reasonably have a long term effect beyond the temporary increase. Present studies if making the stronger claim that there is no relationship on adult performance. Otherwise, agree that is may (or may not).

3. The Flynn effect may well have started earlier for the more affluent subgroups, both in and between nations. A reasonably possibility is therefore that it will also disappear for these groups first. Thus the gap in IQ may dwindle or disappear in the future. Hitsquad seems to agree with me in this regarding the gap between different countries, due to improved nutrition. In the US, differences in breastfeeding may explain some of the B-W gap:
http://www.childtrendsdatabank.org/indicators/90Breastfeeding.cfm

When one controls for SES in the US, the role of genetics is much smaller. Something ignored in many studies done on middle class families:
http://www.mcsba.org/ed_news/fed_issues/federal-national%20news%20items/Socioeconomic%20Status%20and%20IQ.doc .

Regarding the theory "There is zero gain in g from the Flynn effect.", your response to the many papers questioning this by attacking the personal character of one researcher is only embarrassing.

Again, some interesting articles:
http://users.fmg.uva.nl/cdolan/2failures.pdf
http://www3.interscience.wiley.com/cgi-bin/summary/105559992/SUMMARY
http://users.fmg.uva.nl/cdolan/schonem.pdf
http://www.blackwell-synergy.com/links/doi/10.1111/1467-8721.01238
http://journals.cambridge.org/bin/b...UTH=0&500000REQSUB=&REQSTR1=S0021932003000336
http://www.ingentaconnect.com/search/expand?pub=infobike://sage/jbp/2001/00000027/00000002/art00004
http://www3.interscience.wiley.com/cgi-bin/abstract/108565299/ABSTRACT
http://ant.sagepub.com/cgi/content/abstract/2/2/131
http://www3.interscience.wiley.com/cgi-bin/abstract/77003122/ABSTRACT
http://users.fmg.uva.nl/jwicherts/wicherts2004.pdf

 

[Aquamarine]

Is the US black-white gap starting do diminish?

Previous efforts to explain the black-white test score gap have generally fallen short—a substantial residual remained for black students, even after controlling for a full set of available covariates. Using a new data set, we demonstrate that among entering kindergartners, the black-white gap in test scores can be essentially eliminated by controlling for just a small number of observable characteristics of the children and their environment. Once students enter school, the gap between white and black children grows, even conditional on observable factors. We test a number of possible explanations for why blacks lose ground. We speculate that blacks are losing ground relative to whites because they attend lower quality schools, though we recognize that we have not provided definitive proof. This is the only hypothesis which receives any empirical support. To test this hypothesis convincingly, we need more detailed data on schools, neighborhoods, and the general environment kids grow up in.

Compared to previous studies, our results provide reason for optimism. Research on earlier cohorts of children found much greater black-white test score gaps, both in the raw scores and controlling for observables. When we attempt to mimic the nonrandom sample frames in earlier research (for example only looking at low-birth-weight babies, as in IHDP), we continue to find much smaller gaps in our sample. One plausible explanation for the differences between the current sample and cohorts attending kindergarten 10–30 years ago is that the current cohort of blacks has made real gains relative to whites. Recent cohorts show smaller black-white gaps in the raw data, across multiple data sets, which gives reason for optimism.

https://mitpress.mit.edu/journals/pdf/rest_86_2_447_0.pdf

 

[conor dolan]

Dear Mandrake:

There is a fine tradition of ad hominem argumentation in IQ research (I am told that prof. Jensen gets so much of it that these is a special term: “Jensen bashing”). Often such argumentation is the last resource of those who are unable and/or unwilling to consider scientific arguments. I suspect that these individuals are unable, because they do not understands the (often statistical) arguments, or that they are unwilling, because the argument goes against their (political) worldview.

Now, I mention this, because I note that you have stooped to this strategy. You condescendingly dismiss "Jelte Wicherts as a nice young man", but one who does not have "an air of expertise". Ad hominem remarks about how nice Wicherts is, or about his "air" are immaterial to the scientific issue of the Flynn effect. As his supervisor and your fellow scientist, I would appreciate an effort on your part, at least within the confines of public scientific debate, to focus on the contents on Wichert's paper rather than his fine personality, or his "air", expert or otherwise. Perhaps we can leave the personal remarks to those who are unable of unwilling to produce proper arguments? Should you have something sensible to say about Wichert’s results, I am sure he will be happy to bring his expertise to bear on your remarks.

Conor Dolan

 

[hitssquad]

Limits of implications of genotypes, phenotypes and environmental factors

2. One cannot easily measure the iq gap between "races" for the world as whole. Studies done in Africa ignore that many blacks will have lowered iq due to for example inadequate nutrition.

Races are genetically distinct, but genotypes cannot have phenotypic characteristics. A genotype is simply a block, or a typical block of a certain limited generality, of numbers. There can be no universal genetic code for any given level of IQ or for any other phenotypic trait. There can be no universally-adequate nutrition profile or a universally-adequate profile or quantity of any other environmental factor.

Studies done in Africa ignore that many blacks will have lowered iq due to for example inadequate nutrition.

A subject cannot have lowered IQ, or lowered anything else, due to nutrition or anything. A profile of phenotypic traits is what it is. With perfectly-optimal nutrition, any subject would have infinitely high mental ability, if that particular phenotypic trait was the goal of the nutritional optimization. The phrase "lowered IQ" implies that there is a lowering from some optimal level and is nonsensical if optimal level since the optimal level of any trait is theoretically infinitely-perfect and therefore unreachable. Every population on Earth has lower-than-infinitely-high average IQs and therefore might be said to suffer from inadequate diets.

Populations eat whatever they eat. Diet is part of what defines a population. A population's average IQ is whatever it is regardless of diet. Changing the diet might change the IQ, but then you have chaged the population. Scientists studying nutrition in rats demonstrate this all the time. They start with a single population of rats, and then split that population into two or more populations by feeding different diets to different subgroups of the original population.

 

[Mandrake]

First, there are several reasons to believe that those taken as slaves to the US or West Indies (and then many as emigrants to Europe) may have a different and lower average IQ than in Africa.They were only taken from certain costal regions, many from Nigeria. There can be very large differences in measured iq even between close neighbors, like the difference between catholics and protestants in Ireland. Also, there are large iq differences in the same group. Probably, the easiest slaves to capture come from low iq areas and in those areas from those with the lowest iq.

What is your point? Do you wish to have us believe that the genetic lines of US blacks are depressed because their ancestors were less intelligent than other blacks? Is it your belief that blacks in the US are less intelligent than blacks in the countries where their genetic roots lie?

Furthermore, it is known that animals doing simple tasks in agriculture have much lower intelligence than those in freedom. So iq may have declined further in the US during the slave period.

What mechanism would cause a depression in the genetics that determine IQ? Are you telling us that you believe that US blacks were once more intelligent, but because of a period of slavery, they have suffered the presently observed depression that has been measured for the past 100 years? Is there any explanation as to why there has not been a similar depression among other population groups that were subjected to slavery? If there was a "decline" in the US group, it should be evident with respect to the unaffected groups, but we do not see that to be the case, do we?

Is slavery your answer to all group IQ differences? For example, is it the appropriate explanation for Caucasoids having lower mean IQs than Mongoloids? Does it account for the Ashkenazi Jews to Latino IQ gap?

One cannot easily measure the iq gap between "races" for the world as whole.

The "world as whole" would consist of all population groups and would not have a gap with respect to itself. IQ measurements are relative. Since there is no true ratio scale for intelligence, the measurements must be arbitrarily fixed on a given population. From that point, other measurements can be made to show relative differences. It turns out that this procedure is fully capable of providing quantitative measurements that reflect the things that are sought by the measures: differences in learning rates, differences in maximum task complexity that can be attained, differences in job performance, differences in health, and differences in longevity.

Studies done in Africa ignore that many blacks will have lowered iq due to for example inadequate nutrition. Studies done in the US and Europe ignore at least that the blacks there are not a random sample from Africa, as stated above.

Do you believe that African blacks are of equal intelligence to US blacks? Higher? Lower? Your comments above suggest that you want to tell us that the genetic stock of US blacks has a higher mean IQ than is seen in the US, but that African blacks have lower IQs, due to inadequate nutrition. Are you arguing both? If you compare the admixture of US blacks to African blacks, the US blacks have about 25% Caucasoid admixture. Do you think that has any influence over the mean IQ of the US group?

The black-white gap in England is much less than in the US, showing that the US results cannot be applied even to another western country with many blacks descended from slaves.

If you have actual data, please present it and present the analysis of it that shows it to be comparable. For example, if you have real data for blacks in England and want to compare it to blacks in the US, please verify that the genetic lines are essentially identical. The W-B gap was observed prior to the invention of IQ tests and was measured shortly after testing began. British psychometrician Charles Spearman formulated his famous "Spearman's Hypothesis" in 1927, stating that the measured gap would increase as the g-loading of the tests used increased. This has been confirmed. [See Jensen, A. R. (1998). The g factor: The science of mental ability. Westport, CT: Praeger.]

First, I did not ignore you request for explanation. I stated that I agreed with "So, the extent to which the level of g per se has been rising (or falling) over the past few decades remains problematic." This is not incompatible with "The Flynn effect may well have started earlier for the more affluent subgroups, both in and between nations. A reasonably possibility is therefore that it will also disappear for this groups first. Thus the gap in IQ may dwindle or disappear in the future." I only stated that it may, not that it must.

The gap has been around since it was first measured. It is not declining. Some points that have been made by Gottfredson:
The W-B gap is 1.2 SD
Referencing Kaufman& Lichtenberger, 2001: the gap is “Seemingly impervious to time.”
No evidence that IQ gap has changed in last century

The iq studies trying to measure the size of the genetic vs non-genetic factors only applies to the US (and maybe some European countries) variance. Not to US mean, not to variance earlier in US history and not to mean and variance in other countries.

IQ studies are available from various countries. The same parameters apply. All IQ measurements are relative to a given population group. It does not matter which group is selected as the reference point.

There is no reason to exclude iq in childhood and adolescence automatically without evidence.

What studies have excluded "IQ in childhood and adolescence automatically without evidence?" There is considerable evidence to document the appearance and disappearance of shared environmental factors. It is worth noting that these are not large effects.

Most human learning take place in those periods, so even only a temporary increase, for example due to intervention by society, may reasonably have a long term effect beyond the temporary increase. Present studies if making the stronger claim that there is no relationship on adult performance. Otherwise, agree that is may (or may not).

You have made that assertion before, but have not demonstrated that there is any evidence that the small gains that have been reported from adoption or intervention have resulted in higher scores on adult achievement tests, or have contributed to any other verifiable form of adult knowledge gains.

The Flynn effect may well have started earlier for the more affluent subgroups, both in and between nations. A reasonably possibility is therefore that it will also disappear for these groups first. Thus the gap in IQ may dwindle or disappear in the future.

The Flynn effect is an artifact of test instruments and does not show gains in intelligence. The Flynn effect may be observed as a decline in cognitive performance, if scholastic test items are used as the measurement. I provided you with a list of reasons why the Flynn effect is not a Jensen effect. It appears that you do not understand the evidence.