IQ testing envionmental variances

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Arguing that IQ tests are often wrongly described as measuring "innate" rather than developed ability, Jencks & Phillips (1998) conclude that this "labeling bias" causes people to inappropriately attribute the Black-White gap to "innate" differences.[1][dubious – discuss] They assert that non-cultural environmental factors cause gaps measured by the tests, rather than any possible innate difference based on genetics, and to use these tests as a measure of innate difference is misleading and improper.[2][dubious – discuss]

Regarding the IQ gaps in the U.S., there are numerous possible explanations beside genetics. One author lists more than a hundred.[3] It has been suggested that African-American culture disfavors academic achievement and fosters an environment that is damaging to IQ.[4] Likewise, it is argued that the persistence of negative racial stereotypes reinforces this effect. John Ogbu has developed a hypothesis that the condition of being a "caste-like minority" affects motivation and achievement, depressing IQ.[5] Similarly, it is suggested that reduced performance from "stereotype threat" could be a contributing factor.[6]

Estimates of the significance of genetics vs. environment are dependent on the strength of environmental factors. For example, schizophrenia, regarded as being highly heritable[citation needed], has seen increased rates in second and third generation immigrants to Western European countries which do not seem to be the result of increased genetic susceptibility, but another, as yet unidentified, environmental factor(s) that seems to have become more influential[citation needed].

Many anthropologists[who?] have argued that intelligence is a cultural category; some cultures emphasize speed and competition more than others, for example. Speculations about innate differences in intelligence between ethnic groups have occurred throughout history. Aristotle in the 4th century B.C. and Cicero in the 1st. century B.C. disparaged the intelligence of the northern Europeans of the time, as did the Moors in Iberia in the 11th century. [7]

In the developing world there are many factors can greatly decrease IQ scores. Examples include nutrition deficiencies in iodine and iron; certain diseases like malaria; unregulated toxic industrial substances like lead and mercury; and poor health care for pregnant women and infants. Also in the developed world there are many biological factors that can affect IQ. Increased rates of low birth weight babies and lower rates of breastfeeding in Blacks as compared to Whites are some factors of many that have been proposed to affect the IQ gap.[8]

The secular, international increase in test scores, commonly called the Flynn effect, is seen by Flynn and others as reason to expect the eventual convergence of average black and white IQ scores. Flynn argues that the average IQ scores in several countries have increased about 3 points per decade during the 20th century, which he and others attribute predominantly to environmental causes.[9] This means, given the same test, the mean black American performance today could be higher than the mean white American performance in 1920, though the gains causing this appear to have occurred predominantly in the lower half of the IQ distribution.[10] If changes in environment can cause changes in IQ over time, they argue, then contemporary differences between groups could also be due to an unknown environmental factor. On the supposition that the effect started earlier for whites, because their social and economical conditions began to improve earlier than did those of blacks, they anticipate that the IQ gap among races might change in the future or is even now changing. An added complication to this hypothesis is the question of whether the secular IQ gains can be predominantly a real change in cognitive ability. Flynn's face-value answer to this question is "No",[11] and other researchers have found reason to concur.[12] Responding to such concerns, Dickens and Flynn (2001) have proposed a solution which rests on genotype-environment correlation, hypothesizing that small initial differences in environment cause feedback effects which magnify into large IQ differences.[13] Such differences would need to develop before age 3, when the black-white IQ gap can be first detected.[14]

Many studies that attempt to test for heritability find results that do not support the partly-genetic hypothesis (20-80% genetic). They include studies on IQ and skin color,[15] self-reported European ancestry,[16] children in post WWII Germany born to black and white American soldiers,[17] blood groups,[18] and mixed-race children born to either a black or a white mother.[19] Many intervention and adoption studies also find results that do not support the genetic hypothesis.[20] Non-hereditarians have argued that these are direct tests of the genetic hypothesis and of more value than indirect variables, such as skull size and reaction time.[21] Hereditarians argue that these studies are flawed due to their age, lack of replication, problems with their sample population, or that they do in fact support the partly-genetic hypothesis.[22]

Fryer & Levitt (2006), with data from "the first large, nationally representative sample" of its kind, report finding only a very small racial difference when measuring mental function for children aged eight to twelve months, and that even these differences disappear when including a "limited set of controls".[23] They argue that their report poses "a substantial challenge to the simplest, most direct, and most often articulated genetic stories regarding racial differences in mental function."[23] They conclude that "to the extent that there are any genetically-driven racial differences in intelligence, these gaps must either emerge after the age of one, or operate along dimensions not captured by this early test of mental cognition."[23]

Another recent theory hypothesizes that fluid cognition (gF') may be separable from general intelligence, and that gF' may be very susceptible to environmental factors, in particular early childhood stress. Some IQ tests, especially those used with children, are poor measures of gF', which means that the effect of the environment on intelligence regarding racial differences, the Flynn effect, early childhood intervention, and life outcomes may have been underestimated in many studies. The article has received numerous peer commentaries for and against.[24]

[edit] Notes

  1. ^ PBS Jencks Interview "If we change the names of the tests, they still measure the same thing but it wouldn't convey this idea that somehow you've gotten the potential of somebody when you measured their IQ. And I think that creates a big bias, because the people who do badly on the tests are labeled as people with low potential in many people's minds and they sometimes even believe that about themselves."
  2. ^ Jencks & Phillips (1998) "... we find it hard to see how anyone reading these studies with an open mind could conclude that innate ability played a large role in the black-white gap."
  3. ^ Applied Personnel Research: Consulting and Expert Witness Services
  4. ^ Boykin (1994)
  5. ^ Ogbu (1978); Ogbu (2003). See Jensen (1998b), pp. 511-512 for a critique of these arguments.
  6. ^ Steele & Aronson (1995) found that making race salient when taking a test of cognitive ability negatively affected high-ability African American students. They name this phenomenon stereotype threat. Sackett et al. (2004) point out that these findings are widely misinterpreted to mean that eliminating stereotype threat eliminated the Black-White performance gap. See also Cohen & Sherman (2005), Helms (2005), Wicherts (2005) and Sackett et al. (2005) for discussion of the implications of stereotype threat for race and intelligence research.
  7. ^ Aristotle: "Having spoken of the number of the citizens, we will proceed to speak of what should be their character. This is a subject which can be easily understood by any one who casts his eye on the more celebrated states of Hellas, and generally on the distribution of races in the habitable world. Those who live in a cold climate and in Europe are full of spirit, but wanting in intelligence and skill; and therefore they retain comparative freedom, but have no political organization, and are incapable of ruling over others. Whereas the natives of Asia are intelligent and inventive, but they are wanting in spirit, and therefore they are always in a state of subjection and slavery. But the Hellenic race, which is situated between them, is likewise intermediate in character, being high-spirited and also intelligent. Hence it continues free, and is the best-governed of any nation, and, if it could be formed into one state, would be able to rule the world." (Aristotle, Politics, ch. 7).
    Cicero: "Do not obtain your slaves from Britain because they are so stupid and so utterly incapable of being taught that they are not fit to form a part of the household of Athens." Attributed to Cicero's Epistulae ad Atticum (Letters to Atticus), 68 BC-43 BC (latin text). Translation: Cicero (1918).
    "Races north of the Pyrenees are of cold temperament and never reach maturity; they are of great stature and of a white colour. But they lack all sharpness of wit and penetration of intellect." Attributed to "Said of Toledo (a Moorish savant)" by Benedict (1999) (p.34), originally quoted in Hogben (1931).
  8. ^ See Race and intelligence (Explanations)#Nongenetic biological factors
  9. ^ Flynn (1987), Flynn (1987b), Flynn (1999), Flynn (1999b)
  10. ^ Colom et al. (2005)
  11. ^ Flynn (1999)
  12. ^ Wicherts et al. (2004) concluded that "the gains cannot be explained solely by increases at the level of the latent variables (common factors), which IQ tests purport to measure". An analysis by Rushton (1999) found that the IQ increases associated with the Flynn effect did not produce changes in g, which Rushton compares to the finding by Jensen (1998a) that IQ increases associated with adoption likewise do not increase g. Flynn (1999b) disagrees with Rushton's analysis.
  13. ^ Rowe and Rodgers (2002) and others find this hypothesis unsupported by the available evidence. Dickens and Flynn (2002) respond to these criticisms.
  14. ^ Rushton & Jensen (2005a)
  15. ^ Shuey (1966) reported the average correlation between skin color and IQ among American blacks is .1; for comparison Parra (2004) found the correlation between skin color and fraction of West-African ancestry is .4.
  16. ^ Jenkins (1936)
  17. ^ Eyferth (1961); see note below
  18. ^ Scarr et al. (1977), Loehlin et al. (1973)
  19. ^ Willerman et al. (1974)
  20. ^ Nisbett (2005)
  21. ^ Nisbett (2005)
  22. ^ Rushton & Jensen (2005b) argue that these studies are "peculiarly old, the mean year of publication being 1960" and "actually very weak and nondecisive, not having been replicated even once". Jensen (1998b), for example, points out that while the study of children born in post-WWII Germany finds no difference between white and interracial children, it does find a large difference in IQ between boys and girls, suggesting that sampling artifacts have affected the results.
  23. ^ a b c Fryer & Levitt (2006) Testing for Racial Differences in the Mental Ability of Young Children "On tests of intelligence, Blacks systematically score worse than Whites, whereas Asians frequently outperform Whites. Some have argued that genetic differences across races account for the gap. Using a newly available nationally representative data set that includes a test of mental function for children aged eight to twelve months, we find only minor racial differences in test outcomes (0.06 standard deviation units in the raw data) between Blacks and Whites that disappear with the inclusion of a limited set of controls. The only statistically significant racial difference is that Asian children score slightly worse than those of other races. To the extent that there are any genetically-driven racial differences in intelligence, these gaps must either emerge after the age of one, or operate along dimensions not captured by this early test of mental cognition."
  24. ^ How similar are fluid cognition and general intelligence? A developmental neuroscience perspective on fluid cognition as an aspect of human cognitive ability, Behavioral and Brain Sciences (2006), 29: 109-125 Cambridge University Press, Clancy Blair. Multiple comments can be seen on Google Scholar.