Loading ...
Sorry, an error occurred while loading the content.

Re: [evol-psych] Re: Lead: Blacks and Hispanics had relatively high levels

Expand Messages
  • Irwin Silverman
    ... I suppose there might be circumstances where you would want to measure heritability solely within an environmentally deprived group, though I have never
    Message 1 of 19 , Nov 2, 2005
    • 0 Attachment
      On Wed, 2 Nov 2005, J.K. Niemelä wrote:

      > 2005/11/2, weizmann@... <weizmann@...>:
      >
      > > > The fact that heritability increases with age would actually follow from fact
      > > that the effects of environmental toxins such as lead have most of their severe
      > > effects early in development. Hence, the increase in heritability over time
      > > wwould be expected and would says nothing about whether ethnic differences in
      > > IQ are due to such toxins.
      >
      > This is most interesting, since it is at odds with what DW Leake wrote
      > earlier in this thread in defence of lead & micro-nutrient hypothesis.
      > And if the effect of environmental toxins would be this severe on the
      > entire SES & sub-population early in development, this would of course
      > show as high heritability early on (most of the IQ variance within
      > social class and sub-population would be genetic).

      I suppose there might be circumstances where you would want to
      measure heritability solely within an environmentally deprived group,
      though I have never encountered a study so designed. In any case, your
      heritability estimate could not be generalized to the population at large
      and certainly could not be applied to any explanation of differences on
      the variable in question between this group and others, not deprived. The
      proper use of heritability estimates requires sufficient environmental
      variance within the sample.
    • Fredric Weizmann
      IQ scores do not become reliable until the early school age years, while the effects of most environmental toxins occur much earlier than that,often beginning
      Message 2 of 19 , Nov 2, 2005
      • 0 Attachment
        IQ scores do not become reliable until the early school age years, while
        the effects of most environmental toxins occur much earlier than
        that,often beginning during the prenatal period.

        FW

        On Wed, 2 Nov 2005, Irwin Silverman wrote:

        >
        > On Wed, 2 Nov 2005, J.K. Niemelä wrote:
        >
        > > 2005/11/2, weizmann@... <weizmann@...>:
        > >
        > > > > The fact that heritability increases with age would actually follow from fact
        > > > that the effects of environmental toxins such as lead have most of their severe
        > > > effects early in development. Hence, the increase in
        heritability over time
        > > > wwould be expected and would says nothing about whether ethnic differences in
        > > > IQ are due to such toxins.
        > >
        > > This is most interesting, since it is at odds with what DW Leake wrote
        > > earlier in this thread in defence of lead & micro-nutrient hypothesis.
        > > And if the effect of environmental toxins would be this severe on the
        > > entire SES & sub-population early in development, this would of course
        > > show as high heritability early on (most of the IQ variance within
        > > social class and sub-population would be genetic).
        >
        > I suppose there might be circumstances where you would want to
        > measure heritability solely within an environmentally deprived group,
        > though I have never encountered a study so designed. In any case, your
        > heritability estimate could not be generalized to the population at large
        > and certainly could not be applied to any explanation of differences on
        > the variable in question between this group and others, not deprived. The
        > proper use of heritability estimates requires sufficient environmental
        > variance within the sample.
        >
        >
        >
        >
        >
        >
        >
        > Yahoo! Groups Links
        >
        >
        >
        >
        >
        >
      • J.K. Niemelä
        ... The same is true with nutrients. Masters & Lewis lead and alcohol intake & micro-nutrient deficiency hypothesis has of course several more explanatory
        Message 3 of 19 , Nov 2, 2005
        • 0 Attachment
          2005/11/2, Fredric Weizmann <weizmann@...>:
          > IQ scores do not become reliable until the early school age years, while
          > the effects of most environmental toxins occur much earlier than
          > that,often beginning during the prenatal period.

          The same is true with nutrients. Masters' & Lewis' lead and alcohol
          intake & micro-nutrient deficiency hypothesis has of course several
          more explanatory difficulties along with those I have already pointed
          at. One of these problems is due to the Flynn effect. It has been
          empirically shown that there has been a secular rise in IQ in the
          Western countries for 60 years or so. The most plausible key
          explanation for this phenomenon is improvement in nutrition.

          According to Richard Lynn and Tatu Vanhanen (IQ and the Wealth of
          Nations; Praeger 2002, pp.185-6),

          "the secular rises in intelligence that occurred in Western
          populations during the twentieth century are largely attributable to
          improvements in nutrition. Many people who have discussed these rises
          have advanced a number of responsible factors including increases in
          education, greater availability of children's games and toys, greater
          familiarity with intelligence tests, smaller family sizes, greater
          educational attainment of parents, increased urbanization, and changes
          in parental styles of child rearing (reference). All of these factors
          can be ruled out on two grounds. First, the increases in intelligence
          have taken place in four-year-olds, and increases of similar magnitude
          have occurred in the early cognitive development of two-year-olds
          (references). This shows that the causal factors in the secular rise
          of intelligence must have operated before the age of two, and it rules
          out virtually all the effects suggested above such as improvements in
          education, greater availability of children's games and toys, and so
          forth. Second, there have been two studies of pairs of biologically
          unrelated children who were adopted and reared in the same family and
          these have found that there are effectively zero correlations for
          intelligence between these pairs of children when they are adolescents
          and adults. The actual correlations are -0.03 (reference) and -0.09
          (reference). These small negative correlations do not differ
          significantly from zero. The implication of these results is that
          common family influences, such as the extent to which some parents
          have fewer children, sent their children to better schools, give them
          cognitively stimulating toys and computers and so forth, have no long
          term effects on intelligence, because if they did the correlations
          between pairs of biologically unrelated children reared in the same
          family would be positive. The environmental factors determining
          intelligence must be operating before children are adopted, which
          points to the quality of prenatal and early post-natal nutrition.
          There were substantial improvements in the quality of nutrition of the
          populations of the western nations during the twentieth century that
          were responsible for increases in average heights of about one
          standard deviation. The increases in intelligence have been of about
          the same order. Improvements in nutrition brought about increases in
          average brain size and probably also in the brain's neurological
          development."

          Moreover, at least in UK and Denmark, "the increase in scores is
          largely concentrated in the lower segment of the IQ distribution.
          Whatever causes the rise in IQ, it has its greatest effect on those at
          the lower end of the scale, with a corresponding shrinkage of the
          standard deviation" (A.R. Jensen: The g Factor; Praeger 1998, pp.
          319-20).

          These facts do not accord with Masters' & Lewis' lead and alcohol
          intake & micro-nutrient deficiency hypothesis.

          Cheers,
          Jussi
        • Fred Weizmann
          Well, I guess you grant my point that you cannot use the rise in heritability of IQ with age as an argument against the effects of environmental explanations
          Message 4 of 19 , Nov 3, 2005
          • 0 Attachment
            Well, I guess you grant my point that you cannot use the rise in heritability of IQ with age as an argument against the effects of environmental explanations for lower IQ.

            I am not going to get into a long critique of the family studies cited by Lynn here, but I will note that even if the correlations between adopted children and adopted parents was negligable, the mean IQs of the adopted children rose considerably in the direction of the adoptive parents.. This is not a contradiction. Correlations are quite conservative and not the ideal way to demonstrate change. I would never argue that cognition is independent of biology and biological resemblance, as mediated by the gene (and other biological factors), which is what the correlations demonstrate but that it (and intelligence) is plastic and malleable.

            You also seem to contradict yourself. First you say the effects of micro-nutrients are not stable until relatively late in development, but then you ascribe the rise in IQ due to the Flynn effect to the early effects of nutrition.

            Finally, the gap between black and white IQ's in the US began to close in the 1980's, and then rose again. This coincided with the resegregation of the schools in the US. (For more on this, and the lamentable quality of largely black schools in the US, see the recent Jonathan Kozol argicle in Harper's Magazine).

            FW

            J.K. Niemelä wrote:
            2005/11/2, Fredric Weizmann <weizmann@...>:
              
            IQ scores do not become reliable until the early school age years, while
            the effects of most environmental toxins occur much earlier than
            that,often beginning during the prenatal period.
                
            The same is true with nutrients. Masters' & Lewis' lead and alcohol
            intake & micro-nutrient deficiency hypothesis has of course several
            more explanatory difficulties along with those I have already pointed
            at. One of these problems is due to the Flynn effect. It has been
            empirically shown that there has been a secular rise in IQ in the
            Western countries for 60 years or so. The most plausible key
            explanation for this phenomenon is improvement in nutrition.
            
            According to Richard Lynn and Tatu Vanhanen (IQ and the Wealth of
            Nations; Praeger 2002, pp.185-6),
            
            "the secular rises in intelligence that occurred in Western
            populations during the twentieth century are largely attributable to
            improvements in nutrition. Many people who have discussed these rises
            have advanced a number of responsible factors including increases in
            education, greater availability of children's games and toys, greater
            familiarity with intelligence tests, smaller family sizes, greater
            educational attainment of parents, increased urbanization, and changes
            in parental styles of child rearing (reference). All of these factors
            can be ruled out on two grounds. First, the increases in intelligence
            have taken place in four-year-olds, and increases of similar magnitude
            have occurred in the early cognitive development of two-year-olds
            (references). This shows that the causal factors in the secular rise
            of intelligence must have operated before the age of two, and it rules
            out virtually all the effects suggested above such as improvements in
            education, greater availability of children's games and toys, and so
            forth. Second, there have been two studies of pairs of biologically
            unrelated children who were adopted and reared in the same family and
            these have found that there are effectively zero correlations for
            intelligence between these pairs of children when they are adolescents
            and adults. The actual correlations are -0.03 (reference) and -0.09
            (reference). These small negative correlations do not differ
            significantly from zero. The implication of these results is that
            common family influences, such as the extent to which some parents
            have fewer children, sent their children to better schools, give them
            cognitively stimulating toys and computers and so forth, have no long
            term effects on intelligence, because if they did the correlations
            between pairs of biologically unrelated children reared in the same
            family would be positive. The environmental factors determining
            intelligence must be operating before children are adopted, which
            points to the quality of prenatal and early post-natal nutrition.
            There were substantial improvements in the quality of nutrition of the
            populations of the western nations during the twentieth century that
            were responsible for increases in average heights of about one
            standard deviation. The increases in intelligence have been of about
            the same order. Improvements in nutrition brought about increases in
            average brain size and probably also in the brain's neurological
            development."
            
            Moreover, at least in UK and Denmark, "the increase in scores is
            largely concentrated in the lower segment of the IQ distribution.
            Whatever causes the rise in IQ, it has its greatest effect on those at
            the lower end of the scale, with a corresponding shrinkage of the
            standard deviation" (A.R. Jensen: The g Factor; Praeger 1998, pp.
            319-20).
            
            These facts do not accord with Masters' & Lewis' lead and alcohol
            intake & micro-nutrient deficiency hypothesis.
            
            Cheers,
            Jussi
            
            
            
            
             
            Yahoo! Groups Links
            
            <*> To visit your group on the web, go to:
                http://groups.yahoo.com/group/evolutionary-psychology/
            
            <*> To unsubscribe from this group, send an email to:
                evolutionary-psychology-unsubscribe@yahoogroups.com
            
            <*> Your use of Yahoo! Groups is subject to:
                http://docs.yahoo.com/info/terms/
             
            
              
          • J.K. Niemelä
            ... Actually I didn t say anything at all about the probable causes of the lower IQ in lower SES. I just pointed at the problems in trying to explain the
            Message 5 of 19 , Nov 3, 2005
            • 0 Attachment
              2005/11/3, Fred Weizmann <weizmann@...>:

              > You also seem to contradict yourself. First you say the effects of
              > micro-nutrients are not stable until relatively late in development, but
              > then you ascribe the rise in IQ due to the Flynn effect to the early effects
              > of nutrition.

              Actually I didn't say anything at all about the probable causes of the
              lower IQ in lower SES. I just pointed at the problems in trying to
              explain the large-scale, SES-wide lower IQ with micro-nutrient
              deficiency and toxins, since there has been overall secular rise in
              IQ, most of this in lower SES.

              Lynn & Vanhanen suggest that with better nutrition (e.g.
              breast-feeding and vitamins) it is possible to raise the IQ of those
              children at risk to some extent, but as empirical evidence concerning
              the heritability of g clearly shows, not so much that the current
              global/national IQ differences could be eradicated.

              Cheers,
              Jussi
            • rushton@uwo.ca
              Fred Weizman wote that IQ scores do not become reliable until the early school age years, while the effects of most environmental toxins occur much earlier
              Message 6 of 19 , Nov 4, 2005
              • 0 Attachment
                Fred Weizman wote that "IQ scores do not become reliable until the early
                school age years, while the effects of most environmental toxins occur much
                earlier than that,often beginning during the prenatal period."

                Fred, some corrections (again).

                IQ test scores are quite reliable by age 3 1/2 and most Test Manuals show
                this. Also there are many special infant tests of intelligence such as
                visual attention and habituation, such as the ones by Joe Fagan at Case
                Western Reserve University, which predict IQ scores from age seven and up,
                so these can be used quite efficiently for hypothesis testing. Moreover,
                head circumference at birth predicts IQ at age seven, which is one reason
                there are pediatric norms that doctors routinely employ.



                Professor J. Philippe Rushton, Ph.D., D.Sc.
                Department of Psychology,
                University of Western Ontario,
                London, Ontario, N6A 5C2, Canada
                http://www.ssc.uwo.ca/psychology/faculty/rushton_bio.htm
                Tel: 519-661-3685
              • Fred Weizmann
                Phil, You use correlations like other people use white paint: to cover, rather than to reveal. Correlations are notoriously insensitive to mean change, and are
                Message 7 of 19 , Nov 4, 2005
                • 0 Attachment
                  Phil,
                  You use correlations like other people use white paint: to cover, rather than to reveal. Correlations are notoriously insensitive to mean change, and are poor tools to evaluate changes in developmental processes such as intellectual development. Early assessment is primarily done for the purposes of screening (in large part, pushed by US laws mandating early intervention mandated for infants  from 0-3 under the Americans For Disabilities Act.) They do a fair job of screening, but are not designed to function as broad IQ tests across a wide population and a wide range of IQs. They are designed as instruments for developmental assessments, not intellectual assessments although admittedly the line between the two is blurry. Moreover, the performance they sample in very young infants are largely composed of motor and perceptual motor skills but it is language and cognitive performance that provides the best predictors of later IQ. It is the growth in these abilities with age, and their growing representation in the test, that provide for the increasing stability and long term reliabilityof IQ.

                   There are also a number of problems one has in testing infants and very young children. They don't always cooperate, and are very sensitive to environmental conditions. Moreover, in testing premature infants (one of the primary "at risk" groups who would be tested, one has the problems of using chronological age or conceptional age as the baseline for age.)  GP Aylward, who has written widely on the use of infant tests, including the manual for the use of the Bayley Scales, the most widely used infant test, wrote that : "Pressure to quantify development has cause professionals working with infants and young children to attribute a degree of preciseness to developmental screening and assessment that is neither realistic nor attainable."

                  This is not to say that there is no continuity in mental development. Some memory tasks or perceptual tasks may reveal some continuity, and this is probably what Fagan and other researchers are investigating. This does not mean that they are precise or useful enough to use as measures of IQ. Here is the abstract from one very recent study about Fagan's work ( Tasbihsazan R.; Nettelbeck T.; Kirby N.British Journal of Developmental Psychology , Volume 21, Number 4, November 2003, pp. 585-597(13).

                  Abstract:

                  The participants were 78 healthy infants aged 27, 29, 39 or 52 weeks who were tested for visual recognition memory (novelty preference) with the Fagan Test of Infant Intelligence (FTII) and on the Bayley Scales of Infant Development (BSID). Internal consistency of novelty preference from FTII was poor and test–retest reliabilities between 27/29 weeks, 29/39 weeks and 39/52 weeks were low and non-significant. Infants were followed up 1 year later and again at 2 years of age. Correlations between BSID and FTII scores were generally low and non-significant and, with one exception, FTII did not predict later mental outcome. The FTII score at 52 weeks correlated significantly with the Mental Development Index from BSID (1993 edition) at 2 years of age but not with Stanford–Binet scores. This correlation coefficient indicated that the Fagan test might account for up to 24% of the shared variance in later outcomes. Nonetheless, the present study suggested that the clinical utility of the current FTII, as a screening device with infants at risk for slower intellectual development, is limited, because of low sensitivity, which did not exceed 37.5%


                  Fagan may be getting at something important  but this is not exactly a standardized IQ test.

                  The various Wechsler IQ tests provide the "gold standard" of standard IQ tests.No IQ test has better standardization data or is more widely used for testing individuals. For young children, the  most widely used IQ test with preschool children children is the Wechsler Preschool Primary Scales of Intelligence. (the WPPSI). Jerome Sattler, one of the preeminent authorities on the Wechsler family of tests commenting on the recently revised WPPSI commented on the "severely limited breadth of coverage at ages 2-6 to 3-11. With only four subtests in the core batter at the ages, the WPPSI-III is essentially a screening instrument not a comprehensive measure of intellectual ability. The WPPSI-III at these ages does not include measures of memory or quantitative reasoning, which are important components of cognitive development."

                  FW


                  rushton@... wrote:
                  Fred Weizman wote that "IQ scores do not become reliable until the early
                  school age years, while the effects of most environmental toxins occur much
                  earlier than that,often beginning during the prenatal period."
                  
                  Fred, some corrections (again). 
                  
                  IQ test scores are quite reliable by age 3 1/2 and most Test Manuals show
                  this. Also there are many special infant tests of intelligence such as
                  visual attention and habituation, such as the ones by Joe Fagan at Case
                  Western Reserve University, which predict IQ scores from age seven and up,
                  so these can be used quite efficiently for hypothesis testing. Moreover,
                  head circumference at birth predicts IQ at age seven, which is one reason
                  there are pediatric norms that doctors routinely employ.
                  
                  
                  
                  Professor J. Philippe Rushton, Ph.D., D.Sc.
                  Department of Psychology,
                  University of Western Ontario,
                  London, Ontario, N6A 5C2, Canada
                  http://www.ssc.uwo.ca/psychology/faculty/rushton_bio.htm
                  Tel: 519-661-3685
                  
                  
                  
                  
                  
                   
                  Yahoo! Groups Links
                  
                  <*> To visit your group on the web, go to:
                      http://groups.yahoo.com/group/evolutionary-psychology/
                  
                  <*> To unsubscribe from this group, send an email to:
                      evolutionary-psychology-unsubscribe@yahoogroups.com
                  
                  <*> Your use of Yahoo! Groups is subject to:
                      http://docs.yahoo.com/info/terms/
                   
                  
                    
                • Jason Malloy
                  ... A new study by Fagan shows that the correlation between intelligence measured by habituation before the age of 1 and IQ measured after the age of 20 is
                  Message 8 of 19 , Nov 4, 2005
                  • 0 Attachment
                    > Some memory tasks or perceptual tasks may reveal some
                    >continuity, and this is probably what Fagan and other
                    >researchers are investigating. This does not mean that they are
                    >precise or useful enough to use as measures of IQ.

                    A new study by Fagan shows that the correlation between
                    intelligence measured by habituation before the age of 1 and IQ
                    measured after the age of 20 is about .60 (similar to earlier
                    studies between 1 and adolescence).

                    http://www.isironline.org/conference2005.pdf

                    This is different than Bayley's and similar developmental scales
                    which do not predict later IQ, or have a theoretical basis for
                    testing it. In contrast infant habituation tests are clearly
                    measuring more than memory - the content of the tests involves
                    different tasks requiring real problem solving like category and
                    concept formation (similar to what we find in Ravens for adults
                    and what is used in animal intelligence testing).

                    Of course none of this should provide solace to the genetic case
                    as Fagan's tests also show no group differences between white,
                    African-American and sub-Saharan African infants.

                    If this evidence is accepted it also argues against a biological
                    prenatal cause for these IQ differences as well.

                    Infant scales aside, intelligence can reliably be measured by
                    conventional IQ tests at about 3 years of age. Furthermore the
                    entire IQ difference between blacks and whites is found at this
                    age, it is on the g factor and it is 1 SD even after controlling for
                    SES. Though certain tests of unknown IQ significance find a gap
                    of similar magnitude even during the age of 2. see:

                    http://athens.src.uchicago.edu/jenni/klmcarn/
                    FILES/stanford/discrimination_10_22_03_mms.pdf

                    At each age above this blacks and whites are separated by a
                    similar gap up to and after adulthood. Furthermore available
                    adoption studies indicate that blacks and whites raised in
                    affluent white homes are separated by a gap of the same
                    magnitude at adulthood.

                    So some interesting problems come up, if we try to pinpoint
                    environmental causes. If the 15 point IQ gap is caused by racism
                    or similar kinds of effects from society then why does it show up
                    before age 3 in the homes of black parents? But if the IQ gap is
                    caused by black parents (say by lower quality black parenting*)
                    then why do black children raised entirely in upper SES white
                    families grow up to have the same IQ? Is it plausible that two
                    effects (one from society, one from parents) would cause the
                    exact same outcome both independently and in tandem?

                    * Something hinted at by the earlier Moore (1985) adoption study,
                    where black children adopted into black homes had IQs exactly 1
                    SD points below black children adopted into a white home (at an
                    early age).
                  • J.K. Niemelä
                    ... Of course nearly anything can be possible, in theory. But how much of the variance between races or SES, but not within them, do you think could be due to
                    Message 9 of 19 , Nov 5, 2005
                    • 0 Attachment
                      2005/11/2, Rick O'Gorman <rogorman@...>:

                      > I am not clear on how this refutes the possibility of toxins affecting
                      > IQ--that most variation is within families says, to the best of my
                      > knowledge, nothing about the possibility that some variance between
                      > races or SES is due to toxins. The variance within the SES/race could
                      > certainly be due to genetics while differences between SESs could be due
                      > to environmental factors. I don't think there's any inconcsistency here.

                      Of course nearly anything can be possible, in theory. But how much of
                      the variance between races or SES, but not within them, do you think
                      could be due to toxins to have effects of this magnitude? And how
                      could it be possible that effects this massive haven't been detected
                      in previous studies?

                      Please check out the APA Task Force report link in my previous post.
                      But just in case, I shall also copy the relevant part here once again:

                      "A number of conditions in the biological environment have clear
                      negative consequences for intellectual development. Some of these
                      conditions, which are very important when they occur, nevertheless do
                      not contribute much to the population variance of IQ scores because
                      they are relatively rare. (Perinatal complications are one such
                      factor.) Exposure to environmental lead has well-documented negative
                      effects; so too does prenatal exposure to high blood levels of
                      alcohol. Malnutrition in childhood is another negative factor for
                      intelligence, but the level at which its effects become significant
                      has not been clearly established. Some studies suggest that dietary
                      supplements of certain micro-nutrients can produce gains even in
                      otherwise well-nourished individuals, but the effects are still
                      controversial and there has been no long-term follow-up."

                      Moreover, your hypothesis can't explain the following fact:

                      "Racial-ethnic differences are somewhat smaller but still substantial
                      for individuals from the same socioeconomic backgrounds. To
                      illustrate, black students from prosperous families tend to score
                      higher in IQ than blacks from poor families, but they score no higher,
                      on average, than whites from poor families."

                      Source:

                      http://www.udel.edu/educ/gottfredson/reprints/1997mainstream.pdf

                      Cheers,
                      Jussi
                    • Herbert Gintis
                      ... Please give us the studies and the details on predictive ability. I can t remember seeing correlations above 0.4 for such things, and much less for head
                      Message 10 of 19 , Nov 5, 2005
                      • 0 Attachment
                        At 11:19 AM 11/4/2005, rushton@... wrote:
                        IQ test scores are quite reliable by age 3 1/2 and most Test Manuals show
                        this. Also there are many special infant tests of intelligence such as
                        visual attention and habituation, such as the ones by Joe Fagan at Case
                        Western Reserve University, which predict IQ scores from age seven and up,
                        so these can be used quite efficiently for hypothesis testing. Moreover,
                        head circumference at birth predicts IQ at age seven, which is one reason
                        there are pediatric norms that doctors routinely employ.
                                 Please give us the studies and the details on predictive ability. I can't remember seeing correlations above 0.4 for such things, and much less for head circumference.

                        Best,

                        Herbert Gintis




                        Professor J. Philippe Rushton, Ph.D., D.Sc.
                        Department of Psychology,
                        University of Western Ontario,
                        London, Ontario, N6A 5C2, Canada
                        http://www.ssc.uwo.ca/psychology/faculty/rushton_bio.htm
                        Tel: 519-661-3685





                         
                        Yahoo! Groups Links

                        <*> To visit your group on the web, go to:
                            http://groups.yahoo.com/group/evolutionary-psychology/

                        <*> To unsubscribe from this group, send an email to:
                            evolutionary-psychology-unsubscribe@yahoogroups.com

                        <*> Your use of Yahoo! Groups is subject to:
                            http://docs.yahoo.com/info/terms/
                         

                        Herbert Gintis
                        Professor, Central European University, Budapest
                        Visiting Professor, University of Siena, Italy
                        External Faculty, Santa Fe Institute     
                        775-402-4921 (USA Fax)
                        Recent papers are posted on my web site.
                        Get Game Theory Evolving (Princeton, 2000) at Amazon.com
                        Look for Moral Sentiments and Material Interests (MIT Press, 2005)
                        Get Unequal Chances: Family Background and
                          Economic Success (Princeton UP, 2005)
                        Get Foundations of Human Sociality: Economic Experiments
                          and   Ethnographic Evidence from Fifteen Small-scale
                          Societies
                        (Oxford UP, 2004).
                        Quote of the week:
                                  There is no sorrow so great that does not find
                                 its background in joy.
                                                                     Niels Bohr (1938) 

                      • J.K. Niemelä
                        ... Thanks for the interesting paper! But you still seem to miss the big picture concerning the population differences here: how would your hypothesis explain
                        Message 11 of 19 , Nov 6, 2005
                        • 0 Attachment
                          05 Nov 2005 23:52:46 EST, Roger D. Masters <Roger.D.Masters@...>:

                          > To start, however,ending silicofluoride use would have no cost and at least reduce the severity of the racial differences (as well as the level of lead even in white chiodren's blood.)

                          Thanks for the interesting paper! But you still seem to miss the big
                          picture concerning the population differences here: how would your
                          hypothesis explain the fact that the Flynn effect is more pronounced
                          in the lower SES? And those who favour the environmental explanations
                          in IQ differences have said over and over, that the gap between Blacks
                          and Whites is closing. This, of course, is debatable; see Charles
                          Murray's Commentary article:

                          http://www.aei.org/publications/filter.all,pubID.23075/pub_detail.asp

                          How would this (supposed) convergence be possible, if there was this
                          massive negative effect of toxins you hypothesize?

                          And how would your hypothesis explain the fact (sorry for repeating
                          myself!), that
                          "racial-ethnic differences are somewhat smaller but still substantial
                          for individuals from the same socioeconomic backgrounds. To
                          illustrate, black students from prosperous families tend to score
                          higher in IQ than blacks from poor families, but they score no higher,
                          on average, than whites from poor families" (Gottfredson et al. 1997).

                          How enormous do you think the effect of silicofluorides and other
                          toxins should be to cause the difference of one standard deviation (15
                          IQ points) in the mean IQs of Black and White populations? If there
                          was a genotype-environment interaction unfavourable to the Blacks of
                          this magnitude, it would have been detected for sure. But no sign of
                          this in the literature so far (please see once again the relevant part
                          in the APA Task Force report), and oh how many new environmental
                          explanations have continuously been put forward to make the genetics
                          of population differences go away, ever since Arthur Jensen's classic
                          1969 HER article. And yet, after all these years, Jensen's "default
                          hypothesis" still is the most plausible explanation of the big
                          picture, stubborn as ever.

                          Best wishes,
                          Jussi
                        Your message has been successfully submitted and would be delivered to recipients shortly.