Since I’m in Dunedin, New Zealand, I thought I’d write on one of the University of Otago’s most neuroanthropological philosophers, Prof. James Flynn, and dive back into the maelstrom around average IQ scores in different social groups. Prof. Flynn famously pointed out to people outside the standardized testing industry that IQ tests had to be periodically recalibrated because average IQ scores in industrialized countries steadily inflated, suggesting either that people were growing smarter or something else was up with these tests.
Flynn gathered tests from Europe, North America and Asia, around thirty countries in all, and discovered that, for as far back as we had data in any case, average IQ test scores had risen about 3 points per decade and in some cases more. Only recently, in some Scandanavian countries, to the gains appear to be levelling off (see, for example, Sundet 2004; Teasdale and Owen 2005).
We’ve been down this road before at Neuroanthropology before, delving into the murky depths of group averages and tests scores. Back in December 2007, Agustín offered neuroanthropology and race- getting it straight, following up on a discussion sparked by Daniel’s post, IQ, Environment & Anthropology. I put in my two cents, and caught an ear-full, for Girls closing math gap?: Troubles with intelligence #1 (the first ‘part’ of this post). I’ve been wanting to re-enter this particular body of hot water since I read a story on Science Daily, Plastic Brain Outsmarts Experts: Training Can Increase Fluid Intelligence, Once Thought To Be Fixed At Birth, so against my better instincts, my shoes are off and I’m poking my toes in.
Ironically, in spite of the fact that children spend longer on average in school than in previous decades, the Flynn Effect does not show up on the parts of standardized tests that measure school-related subjects. That is, tests of vocabulary, arithmetic, or general knowledge (such as the sorts of facts one learns in school) have showed little increase, but scores have increased markedly on tests thought to measure ‘general intelligence’ (or ‘g’), such as Raven’s Progressive Matrices which require mental manipulation of objects, logical inference, or other abstract reasoning.
The Flynn Effect has been one of the most powerful refutations to those who think that intelligence is ‘innate’ or ‘genetically determined’ because it’s very hard to argue that the genetic pool of a population can improve over time; if genes determine intelligence, how can the average in a population be increasing? Theoreticians called ‘IQ fundamentalists’ by some commentators have put forward a number of arguments about innate intelligence, virtually always pessimistic about minority groups, and often seeking to decrease funding for programs like Head Start that seek to ameliorate inequalities in academic achievement (see for example, Malcolm Gladwell’s discussion of ‘IQ fundamentalists’ in his review of Flynn’s What Is Intelligence? in The New Yorker from around this time last year.
Jon S. Twing at TrueScores pointed out in a post, IQ and the Flynn Effect, that, when he was working on the Third Edition of the Wechsler Intelligence Scale for Children (WISC-III), he was fascinated with a process called ‘continuous norming.’ Twing writes that continuous norming was a process developed by Prof. Richard Gorsuch and applied by Dr. Gale Roid ‘to improve the precision of empirical norms.’ In other words, people directly involved in the design and evaluation of these tests realized that these scores had to be adjusted, but Flynn noticed these changes and drew more widespread attention as well as some fascinating theoretical conclusions from this trend.
A number of explanations have been put forward for the Flynn Effect, including improved nutrition, smaller families which provide more adult interaction for children, greater familiarity with standardized tests, better schooling, and more complicated cognitive environments. Flynn has offered his own explanations in recent publications, which we will return to in a moment because they offer us a nice entry point into the neuroanthropology of ‘intelligence’.
The Flynn Effect runs contrary to our usual pessimism about the intelligence of ‘kids these days.’ As Steven Johnson wrote in Wired, ‘Despite concerns about the dumbing-down of society – the failing schools, the garbage on TV, the decline of reading – the overall population was getting smarter.’ Asked point blank about the alleged intellectual degradation of contemporary life, Flynn has been very abrupt in pushing back against this (see, for example, Matt Nippert’s story on Flynn from the New Zealand Listener). Flynn’s less cynical about IQ testing (although he recognizes its limitations) than he is interested in the underlying cognitive changes that these scores might reflect.
Four paradoxes of the Flynn Effect
In his book, What Is Intelligence?, Flynn identifies four paradoxes that arise from the steady increase in average IQ test scores given the predominant understanding of ‘intelligence.’
The factor analysis paradox: Prior research suggested that a single factor, ‘general intelligence’ or ‘g,’ underlies IQ. The Flynn Effect, however, does not affect all sections of the WISC and other intelligence tests to the same degree; that is, if we’re getting smarter, some parts of our intelligence are getting smarter faster, undermining our confidence in ‘g.’
The intelligence paradox: The Flynn Effect suggests that we are getting smarter relatively quickly, but it’s not obvious (and some would say flies in the face of certain evidence) that kids today are so much smarter than their parents or grandparents (except perhaps when it comes to home electronics). As Flynn writes:
If huge IQ gains are intelligence gains, why are we not stuck by the extraordinary subtlety of our children’s conversation? Why do we not have to make allowances for the limitations of our parents? A difference of some 18 points in the average IQ over two generations ought to be highly visible.
The mental retardation paradox: If the rate of change in IQ is extrapolated backwards, it suggests that people in 1900 had a mean IQ score somewhere between 50 and 70 judged by today’s standards. An IQ level of 75 is typically considered ‘mentally retarded.’ Flynn puts this one nicely, too: ‘Either today’s children are so bright that they should run circles around us, or their grandparents were so dull that it is surprising that they could keep a modern society ticking over.’
The identical twins paradox: Twins raised apart tend to have very similar IQ scores, typically considered strong evidence for a genetic basis for differences in IQ. The Flynn Effect instead suggests that intelligence, if it is being measured by IQ, is more malleable and subject to environmental effects.
Unraveling the paradoxes
According to Flynn, one possible set of explanations (certainly not the only one) is the following:
Functional independence of intelligences: The appearance of a general intelligence, ‘g,’ underlying all the subsections and different cognitive skills on a test like the WISC, is an effect of the test in a static social context. Over time, because shifts occur in the emphasis placed on different aspects of intelligence, different cognitive skills, the relative strengths of the various dimensions can shift. In his talk at the University of Cambridge, Flynn uses the example of an ‘athletic g’ for all the events of the decathlon to discuss how traits that are functionally interdependent might appear to correlate (see also Dickens and Flynn 2001).
Non-uniform intelligence gains: As Flynn writes: ‘The 20th century has seen some cognitive skills make great gains, while others have been in the doldrums.’ Whether or not our scores are increasing, and how much, depends very much upon which cognitive skill we’re testing. He offers a very interesting discussion of the variation in rates of improvement (or even decrease) here. As Flynn explains:
IQ gains over time describe a dynamic situation in which social priorities shift in a multitude of ways. No better maths teaching, more leisure but with the extra leisure devoted to visual rather then verbal pursuits, the spread of the scientific ethos, and a host of other things all occurring together. The average on Similarities rises but the average on Arithmetic and Vocabulary does not.
Increasing skills in abstract thought: Flynn points out the obvious – our ancestors were not mentally retarded. But they also were adept at different sorts of mental skills, an issue I’ll return to a bit later. Flynn suggests that we have become more adept at certain kinds of formal, hypothetical, and logical reasoning, liberating our problem solving ability from concrete reference (something that can be a detriment in certain sorts of problem-solving, as well).
Twins actually generating shared environment: Part of the reason genetic factors appear dominant in some traits is that some of these genetic traits attract certain environmental factors that compound and reinforce the genetic differences. The example given in the Wired article on the Flynn effect is the way that a genetically-based advantage in height might lead two identical twins, separated at birth, to wind up in environments where they both get pretty good at basketball; see the discussion here, too or in Dickens and Flynn 2001). As Flynn writes: ‘genetic advantages that may have been quite modest at birth have a huge effect on eventual basketball skills by getting matched with better environments — and genes thereby get credit for the potency of powerful environmental factors, such as more practice, team play, professional coaching.’
Flynn, together with William T. Dickens (2001), provided a more rigorous mathematical model of the ways in which reciprocal causation and social multipliers could confound the contribution of genetics and environment to IQ, but also found that many factors that influenced childhood IQ scores might not affect adult IQ without change in adult environment to reinforce changes. Because a person’s genotype affects their environment, a potentially small difference in the genetic contribution to intelligence might, through feedback effects, get compounded into a large difference in performance on a standardized test. In addition, there would be social effects if those around you would be developing more sophisticated cognitive abilities; you would both be influenced by them and expected to live up to the new norm in ability.
So do we give up on IQ tests?
Flynn doesn’t think gains in IQ scores are either trivial or cause for discounting standardized testing; the tests are not fatally flawed, although our understanding of the results may be. Flynn argues that we really need to understand what these changes are measuring. People are not growing ‘smarter,’ they are growing better at very specific cognitive skills:
This solution to our paradox does not imply that massive IQ gains over time are trivial. Aside from the escalation in lateral thinking, they represent nothing less than a liberation of the human mind. The scientific world-view, with its vocabulary, taxonomies, and detachment of logic and the hypothetical from concrete referents, has begun to permeate the minds of post-industrial people. This has paved the way for mass education on the university level and the emergence of an intellectual cadre without whom our present civilization would be inconceivable. (from this page in the Cambridge talk)
Flynn surveys a number of studies that suggest that the ability to engage in formal or abstract reasoning strongly correlates, not with intelligence, but with the level of schooling; since, in the West, people stay in school longer if they are more intelligent, it makes sense that the correlation between intelligence and the ability to engage in abstract reasoning would be especially strong in industrialized countries. That is, if schooling affects intellectual abilities measured by these tests, at the same time that these tests provide greater access to formal educational opportunities, then the tests would measure intelligence really well, but not just because they transparently reflect some underlying intelligence. Rather, it would be because the tests themselves are tied up in a self-reinforcing cycle of talent (or its lack) being compounded by opportunities, confidence, and motivation (or their opposite).
Innovations in thinking
Flynn argues that certain shorthand abstractions (SHA), formulae for thinking critically, have entered the cognitive repertoire of educated people, expanding their intellectual capabilities. Ironically, none of these SHAs shows up on a standardized IQ test like WISC or WAIS. If we wanted to measure people’s critical thinking abilities, we would have to come up with a new sort of test.
In a brief form, the concepts (along with the date of their creation and intellectual discipline) include: ‘market’ (1776, economics), ‘percentage’ (1860, statistics), ‘natural selection (1864, biology), ‘control group’ (1875, social science), ‘random sample’ (1877, social science), ‘naturalistic fallacy’ (1903, moral philosophy), ‘charisma effect’ (1922, social science), ‘placebo’ (1938, medicine), ‘falsifiable/tautology’ (1959, philosophy of science), and ‘tolerance school fallacy’ (2000, moral philosophy) (okay… the last one is Flynn’s, but it really builds upon some concepts close to our anthropological hearts, like cultural relativism). I won’t go into any detail (you can read about them here), but the idea is that some concepts that become shared representations – although by no means universal – facilitate forms of thought that are otherwise unlikely, or even impossible.
Flynn also offers a short, incomplete list of some of the concepts that resemble shorthand abstractions, but are actually opposed to scientific thought; among the examples he offers are the idea that some human traits are ‘contrary to nature’ (usually something the speaker want so condemn), ‘intelligent design’, ‘gender science’, and ‘reality is a text’, a nice mix of targets guaranteed to irritate a majority of readers: as Flynn writes, they are ‘evenly divided between the contributions of obscurantist churches and contemporary academics.’
Whether or not we agree about any one of these SHAs (or anti-SHAs, call them ‘shorthand errors’ or SHEs), Flynn’s account is a powerful discussion of how cognition might be affected by social invention, cognitive sharing, and even historical development of thought. Rather than getting ‘smarter’ in some vague way, Flynn offers a much more concrete account of specific thinking tools that individuals may or may not successfully integrate into their repertoire. They clearly have blinders as well as lenses, obscuring certain things or making it harder to have some kinds of thought, as well as facilitating others (like the ways of thinking tested on the WISC and other IQ tests). Although I may quibble with this or that SHA, I admire the degree to which he pins them down, even locating their origin and birth. It’s a kind of intellectual history that’s a bit alien to me as an anthropologist, but I think it’s very persuasive.
I’ll come back later and argue about whether ‘modern’ is such a good term to call it, but given this sophisticated, historical, contingent account of the very specific concepts that the term refers to in Flynn’s theory, I think it works. Perhaps it’s not fortuitous as sloppy thinkers are not going to read the details but possibly assume a very old fashioned ‘the West and the Rest’ division of the world into ‘modern thinkers’ and ‘non-modern thinkers,’ but I can’t accuse Flynn of doing that.
Flynn wrapped up his talk at the University of Cambridge with a discussion of wisdom, whether or not the industrial revolution that produced gains in IQ makes us so materialistic that wisdom will not be able to curb destructive desires. He wonders openly about the future:
The 20th century has been the century of rising IQ, the spread of the language and categories of science, the liberation of reason from the concrete, and the enhancement of on-the-spot problem solving. The 21st century will be the battleground of armies for and against the SHAs. It just might culminate in the triumph of critical thinking if universities hold fast to what they are supposed to be all about. Whether we can hope for anything more, I cannot predict.
Now, I still haven’t gotten to that article on Science Daily on the training of fluid intelligence that started me down this path, but don’t worry, I’m just getting warmed up. I’ve got more to come on training intelligence and whether or not rural people are dumber than city-dwellers… Yeah, it’s just getting good.
Thanks to Sue Sheridan who hipped me to the Science Daily piece that made me make my first notes for this posting — and our readers should check out her blog, Life of Wiley, home of the Daily Skeleton Action figure.
Dickens, William T., and James R. Flynn. 2001. Heritability Estimates Versus Large Environmental Effects: The IQ Paradox Resolved. Psychological Review 108(2): 346-369. doi:10.1037//0033-295X. 108.2.346
Flynn, James R. 1984. The mean IQ of Americans: Massive gains 1932 to 1978. Psychological Bulletin 95: 29-51.
_____. 1987. Massive IQ gains in 14 nations: What IQ tests really measure. Psychological Bulletin 101: 171-191.
_____. 1998. IQ gains over time: Toward finding the causes. In U. Neisser, ed., The rising curve: Long-term gains in IQ and related measures. Pp. 25 – 66. Washington, DC: American Psychological Association.
_____. 2000. IQ gains, WISC subtests, and fluid g: g theory and the relevance of Spearman’s hypothesis to race (with Discussion). In G. R. Bock, J. A. Goode, & K. Webb, eds., The nature of intelligence. Pp. 222-223. Novartis Foundation Symposium 233. New York: Wiley.
_____. 2007. What Is Intelligence?: Beyond the Flynn Effect. Cambridge: Cambridge University Press.
Gladwell, Malcolm. 2007. None of the Above: What IQ Doesn’t Tell You About Race. The New Yorker (December 17, 2007).
National Science Foundation. 2008. (June 6). Plastic Brain Outsmarts Exp
erts: Training Can Increase Fluid Intelligence, Once Thought To Be Fixed At Birth. ScienceDaily. Retrieved June 7, 2008, from http://www.sciencedaily.com /releases/2008/06/080605163804.htm
Sundet, Jon Martin. 2004. The end of the Flynn Effect. A study of secular trends in mean intelligence scores of Norwegian conscripts during half a century. Intelligence 32: 349. doi:10.1016/j.intell.2004.06.004.
Teasdale, T. W., and D. R. Owen. 2005. A long-term rise and recent decline in intelligence test performance: The Flynn Effect in reverse. Personality and Individual Differences 39(4): 837–843. doi:10.1016/j.paid.2005.01.029
University of Michigan. 2008. (May 6). Brain-training To Improve Memory Boosts Fluid Intelligence. ScienceDaily. Retrieved June 7, 2008, from http://www.sciencedaily.com /releases/2008/05/080505075642.htm
13 thoughts on “The Flynn Effect: Troubles with Intelligence 2”
FLYNN EFFECT + ‘g’ – MY CONFUSION!?
You write that “scores have increased markedly on tests thought to measure ‘general intelligence’ (or ‘g’)” – ie that the Flynn Effect primarily affects ‘g’.
But (some!) IQ researchers say the opposite of that – ie that “the Flynn Effect is not on the g factor”. At least that is what Rushton and Jensen say…!
What is the strongest bit of evidence that they are wrong about this and that the Flynn Effect is mainly on the g-loaded bits of IQ tests?
This might be something that you’ve already made clear in this post – but being a non-scientist I struggle somewhat to get my head round all the evidence in this contentious area.
This was excellent and I anxiously await the next post. As an aside, a few months back I had an interview with Charles Murray (The Bell Curve) on Neuronarrative. He’s obviously had much to say about IQ, ‘g’ and related topics, and in his latest book he makes some very contentious arguments concerning levels of intelligence among children and the role of education. If you get a few minutes, take a look, I’d like to know your take on what he has to say (it’s under the ‘Interviews’ tab).
Again, great post.
How intelligent are intelligence scales?
From an anthropological point of view cognitive scientists are being less than rational when they treat intelligence scales as though they are measuring something fundamental and innate in human beings. No doubt innate abilities are used by people when they tackle IQ tests, but it is unlikely that such abilities evolved under selection pressure for this kind of problem solving.
Intelligence scales are culturally embedded artifacts designed to meet the idiosyncratic needs of postindustrial western societies, and reflect the equally idiosyncratic assumptions found in the west – such as our habit of referring to someone as “brainy” when we mean “intelligent”, and the widely held assumption that brains got bigger during human evolution because of selection pressure for “intelligence” (and/or language: e.g. Deacon 1992). The idea that human intelligence is the ultimate pinnacle of biological evolution may be little more than colonialist propaganda, suggesting that “scientific” societies are the ultimate pinnacle of cultural evolution – and hence morally entitled to dominate others who formerly managed perfectly well without the blessings of “modernity”.
Sir Francis Galton devised the first intelligence test in the late 19th century and this was followed by the scale developed by Alfred Binet and Théophile Simon between 1905 and 1911 (Atkinson et al., 1993: 457-8). As early as 1884 Galton examined more than 9,000 visitors to the London exhibition and found to his chagrin that eminent British scientists could not be distinguished from ordinary citizens on the basis of head size (ibid: 458). From that point on the kind of assumptions made by Galton have continued to pervade scientific thinking with little or no empirical encouragement.
A curious more recent example is the spate of papers attempting to correlate brain size with “intelligence” as assessed by (notably) the Wechsler Adult Intelligence Scale (Andreason et al., 1993 ; Egan et al., 1994, 1995; Peters, 1995; Flashman et al., 1998; Rushton & Ankney, 1995, 1996, 2000; Vernon et al., 2000; Thompson et al., 2001; MacLullich et al., 2002; Staff, 2002; Drachman, 2002). Some of this research has provoked controversy over issues of anthropological concern, including ethnocentrism, sexism, and racism (Peters, 1995; Rushton & Ankney, 1995, 1996). Researchers did indeed find a positive correlation and this has been acclaimed as a vindication of the studies and the underlying ideology of “big-brained people are smarter” (McDaniel, 2005). In point of fact, a meta-analysis of 37 studies, involving 1,530 people, yielded a best estimate for the population correlation (r) of 0.33 (McDaniel, 2005), suggesting that the intelligence factors measured are associated with around 11% (r2) of brain volume, and cannot account for the bulk of brain expansion during the last 2.5 million years.
Why the scientists concerned should feel they have achieved something useful becomes all the more mysterious when you realize that many components of the scales used assess culturally acquired skills which were invented in historic times – particularly numeracy and written language (other questions address institutionalized factors such as money and banking, and none can be claimed with confidence to be free from cultural conditioning). Many preliterate societies even today lack numbers higher than two, and others no higher than five. Numeracy and literacy originated with the bureaucratic needs of the first civilizations along the river valleys of the Nile, Tigris, Euphrates, Indus, Ganges, and the Yellow River in China. These of course post-date the agricultural revolution (around 10,000 years ago).
An analysis of 217 fossil crania (De Miguel & Henneberg, 2001) – the largest sample we have to date – suggests that average human cranial capacity just prior to the agricultural revolution was around 1,500 cm3, which is about 12% larger than the average human capacity today (1,340 cm3). In other words, intelligence scales measure abilities that developed at a time when brains were most probably getting smaller, and any correlation between such abilities and brain size is less than informative (since it serves only to reinforce current biases in cognitive science). All these studies would seem to be a prodigal waste of research funding and resources – a waste that could easily have been avoided with a little anthropological input.
Currently the dominant theory of brain expansion in primates is the social or Machiavellian intelligence hypothesis, which holds that social intelligence makes greater cognitive demands than object intelligence. So why did all these researchers choose individualistic instruments such as the Wechsler scale (1939) rather than, say, Gardner’s (1983) measures of “six intelligences”? Gardner argued that social, musical, artistic, and “bodily-kinaesthetic” (including dance and sports) skills have been important since the “dawn of civilization” whereas logical scientific thought only came to the fore after the European Renaissance (Atkinson et al., 1993: 476). But the very term we use to define our species – Homo sapiens – presupposes an evolutionary trajectory ultimately directed towards the production of scientists.
The idea of a “general” (as opposed to social) intelligence is at best dubious. The point can be illustrated by a brain scanning study which contrasted “theory of mind” (ToM) with “non-ToM” stories and cartoons (Gallagher et al., 2000). The investigators assumed that brain structures activated by non-ToM stories and cartoons were “general reasoning” areas, and only those uniquely activated by ToM stories and cartoons were “ToM” (i.e. social reasoning) areas. They concluded that ToM involves a rather small area in ventromedial prefrontal cortex. However, the “general reasoning” areas were much more strongly activated during ToM than non-Tom tasks. It would seem more reasonable to infer that “general reasoning” involves a subset of social reasoning areas, and that “general intelligence” is a spin-off benefit of social intelligence. Animals which score most highly in laboratory studies of intelligence and language are invariably highly social – such as chimpanzees, dolphins, and Congo grey parrots.
The discovery of the Flynn effect should have alerted us by now to the culturally conditioned limitations of western intelligence scales. These tests may predict academic performance in western institutions, but they cannot provide reliable information about innate functions of the human brain. More plausible views of the social brain and human brain expansion (in my opinion, of course) can be found at http://www.socialmirros.org. The Human Evolution page is not yet up, but relevant papers are referenced on the Social Brain page and my own papers can be downloaded from here and from my CV (see About Charles Whitehead: Publications).
Andreasen, N. C., Flaum, M., Swayze II, V., O’Leary, D. S., Alliger, R., Cohen, G., et al. (1993) ‘Intelligence and brain structure in normal individuals’, American Journal of Psychiatry, 150, 130–4.
Atkinson, R.L., Atkinson, R.C., Smith, E.E., Bem, D.J. (1993) Introduction to Psychology (Fort Worth: Harcourt Brace).
Deacon, T.W. (1992) ‘The human brain’, in Jones, S., Martin, R., Pilbeam, D., eds., The Cambridge Encyclopedia of Human Evolution (Cambridge: Cambridge University Press) pp. 115-23.
De Miguel, C. & Henneberg, M. (2001) ‘Variation in hominid brain size: How much is due to method?’, Homo, 52 (1), pp. 3-58.
Drachman, D.A. (2002) ‘Hat size, brain size, intelligence, and dementia’, Neurology, 59, 156-157.
Egan, V., Chiswick, A., Santosh, C., Naidu, K., Rimmington, J. E., & Best, J. J. K. (1994) ‘Size isn’t everything: A study of brain volume, intelligence and auditory evoked potentials’, Personality and Individual Differences, 17, 357–367.
Egan, V., Wickett, J. C., & Vernon, P. A. (1995). Brain size and intelligence: Erratum, addendum, and correction. Personality and Individual Differences, 19, 113–115.
Flashman, L. A., Andreasen, N. C., Flaum, M., & Swayze, V. W. (1998) ‘Intelligence and regional brain volumes in normal controls’, Intelligence, 25, 149–160.
Gallagher, H.L., Happé, F., Brunswick, N., Fletcher, P.C., Frith, U., Frith, C.D. (2000) `Reading the mind in cartoons and stories: an fMRI study of “theory of mind” in verbal and nonverbal tasks’, Neuropsychologia 38, 11–21.
MacLullich, A. M. J., Ferguson, K. L., Deary, I. J., Seckl, J. R., Starr, J. M., & Wardlaw, J. M. (2002), ‘Intracranial capacity and brain volumes are associated with cognition in elderly men’, Neurology, 59, 169–174.
McDaniel, M.A. (2005) ‘Big-brained people are smarter: A meta-analysis of the relationship
between in vivo brain volume and intelligence’, Intelligence, 33, 337-46.
Michael A. McDaniel
Peters, M. (1995) ‘Does brain size matter? A reply to Rushton and Ankney’, Canadian Journal of Experimental Psychology; 49 (4).
Rushton, J.P. and Ankney, C.D. (1995) ‘Brain size matters: A reply to Peters’, Canadian Journal of Experimental Psychology; 49 (4).
Rushton, J. P., & Ankney, C. D. (1996) ‘Brain size and cognitive ability: Correlations with age, sex, race, social class, and race’, Psychonomic Bulletin and Review, 3, 21–36.
Rushton, J. P., & Ankney, C. D. (2000) ‘Size matters: A review and new analyses of racial differences in cranial capacity and intelligence that refute Kamin and Omari’, Personality and Individual Differences, 29, 591–620.
Staff, 2002 Staff, R. T. (2002). Personal communication to Michael A. McDaniel on November 11, 2002.
Thompson, P. M., Cannon, T. D., Narr, K. L., Erp, T. V., Poutanen, V. -P., Huttunen, M., et al. (2001) ‘Genetic influences on brain structure’, Nature Neuroscience, 4 (12), 1253–1258.
Vernon, P. A., Wickett, J. C., Bazana, P. G., & Stelmack, R. M. (2000) ‘The neuropsychology and psychophysiology of human intelligence’, in R. J. Sternberg (Ed.), Handbook of intelligence (New York: Cambridge University Press) pp. 245-64.
Nice post, but for the love of god make the snowflakes go away – they are very distracting.
Dear neuroanthropfolks,and Prof Flynn,
IQ or g factor and all those IQ things are highly inherited ( heritability 0.7 to o.9) human behavioral traits (please no more bickering about this). Now,thinking quantitative-genetic-ally, those highly inherited traits can easily and rapidly be changed or increased by applying selection for the trait. Since the human society invented methods to educate people to improve their intelligence, they unintentionally applied selection for the improvement of all those IQ-related traits ( multiple-intelligence) all may have different heritabilities with small insignificant differences. Applying selection by forcing every one/students at different degree of schooling, starting with entrance tests, semester examinations and final exams to graduate at the Master and the highest degree PhD doctorate degree level. All those testing are a selection process for higher intelligence of human beings. Like natural selection in the wild for survival of the fittest, the unfit humans who did not pass the test are those whith low grades or IQ and have to be dropped outs. Now when traits with high heritabilities are being tested, the result is a large selection respons (a quantitative genetics jargon)or gains. The higher the heritability and the tougher the test the higher also will be the response.The graduates passing all the tests are the chosen ones with high IQ test scores. The higher % of graduates, the higher average IQ/g test scores, thus the Flynn Effect is resolved with no paradoxes. Sinse the IQ increse rate in the past formed sigmoid (s)curve (curvelinear),starting slow, a fast middle and leveling off in the end, a straight line backward extrapolation is thus not valid. So there goes our retarded grand Pa & Ma. Yes IQ is maleable only by applying selection, nothing else, environmental interventions only change the phenotypic IQ not the genetic effects inherited from both parents. Parents practicing positive assortative mating (chosing class mates graduates as spouse), seemed to help modern industrial populatins to gain faster IQ gains. Well that will suffice to solve all of the mysteries and paradoxes of fast IQ gains. This may be what God The Allmighty (Allah SWT) has willed to happen upon us in this world. So don’t worry no more Greg and Mr Flynn, let there be bigger Flynn Effects in this world. Thank you all for reading this lengthy chronic comment.
DEAR Mr Greg Downey on second thought I should have to reveal some of my background information . I am like prof Flynn a retired professor also in another field which is Animal Breeding an Genetics, been reading a lot of the IQ literature and found out that animal breeding and genetics, which turned out to help me much in comprehending problems and disputes and a lot of unforgivable waste of time just becouse one’s lack of background in quantitative genetics. Thanks a lot.
I am not a scientist. And am retired (not a professor). Just reading about Flynn Effect, just to satisfy curiosity. This is the place I found most interesting discussion that made me to just type two or three words. My knowledge gained with one week browsing tells me that prof. Harimurti Martojo has given the clue to the problems. Now I can stop my broesing on the topic. Thank you all.