Storfer (2000) offers a sweeping overview and interesting possible interrelations between several ongoing population trends. However, the argument rests on some weak pillars which need more research, particularly the so far limited evidence that brain size correlates with intelligence and that the increasing average raw IQ scores actually represent increasing intelligence. The target article has great heuristic value in that it suggests a focus on more population trends and more research on how they may be linked. Humanity has been conducting various societal experiments over the 20th Century. These may be having a number of effects, as yet undetected.
2. The article also adds another possible dimension to the expanding literature on the "Flynn effect"; the long-term rise in raw IQ scores (e.g. Flynn, 1984; Neisser, 1998). Researchers traditionally have assumed that the rise is entirely environmentally induced because any genetic changes through natural selection seemed too slow to operate over the short time scale. Indeed, the eugenics view from early in the 20th Century, is that selection pressures have been for lower intelligence (e.g. Lynn, 1996). The view is that the less intelligent have been producing more children, given that many professional couples nowadays have few or no children. The argument goes that an environmentally induced rise in IQ scores has been masking an underlying worsening of the gene pool for intelligence (Lynn, 1996).
3. It seems likely, however, that if such genetic means as those Storfer proposes in fact contribute to the IQ rise, they just constitute one of many other variables that do so, each perhaps adding a little (e.g. Jensen, 1998). The others probably include all the factors known to raise IQ score which have improved in Western society, such as health, nutrition, environmental stimulation, education, and so on (Neisser, 1998; Howard, in press). A particularly interesting study of the effects of some such factors, which predates Flynn's own work by a long time, is from Wheeler (1942). He looked at the IQ scores of school children in the Tennessee mountains over ten years. The region changed from a very under-stimulating rural environment with one-teacher schools to a much more developed one, and the average IQ score rose by about 10 points. Similarly, Cahan and Cohen (1989) show an effect of just one year of education.
4. I do have a few concerns about the target article. Some pillars of Storfer's general argument are shaky and need further empirical support. First, the link between brain size and intelligence remains controversial. While some brain imaging studies lend some support to the notion, much more research is needed on it.
5. Second, it is still not certain whether the IQ rise really represents an increase in Spearman's g. Flynn himself (e.g. 1984; 1999) has long argued that only some peripheral ability that improves test scores is rising, such as "abstract problem solving ability". He argues that children are just getting better at some minor ability that helps them do IQ tests. Neisser (1997) suggests that perhaps visuospatial ability is increasing, because children now live in a much more visually rich world.
6. This issue has great theoretical and practical importance, and not just as a pillar of Storfer's argument. It has been much discussed, but is extremely difficult to settle. One approach is to find evidence in the real world that people are getting smarter. The large IQ score rises should be having profound effects. Flynn (1987) initially reported none, citing no evidence of more gifted children and decreased numbers of patents granted over time. People do not seem to be getting smarter, he argued. However, it is far from clear what would happen if intelligence was rising, how it would manifest in the real world. Intelligence is only one factor in achievement (Simonton, 1999). Also, there is no obvious way to test the issue experimentally, only with correlational studies, with all their inherent problems of trying to ascertain causation of changes over long periods.
7. The limited evidence available is consistent with the view that intelligence really is rising. There is the logical evidence that IQ test scores correlate well with real-world performance and that factors known to raise IQ are indeed improving in Western populations. The technological world gets ever more complex, but the young seem able to cope. A greater proportion of the population now goes on to university. Some anecdotal evidence is that the soldiers learned military skills much faster in World War 2 than in World War 1 (Jensen, 1998). Also, test sophistication tends to produce a rise of perhaps 5-6 points (e.g. Kulik, Kulik, & Bangert, 1984) and any rise due only to that should have stopped long ago.
8. Several formal studies also suggest intelligence is rising. Rosenau and Fagen (1997) found increased "integrative complexity" (a measure of text sophistication) in texts written between 1916-32 and 1970-93. Howard (1999; in press) found several other indicators; the prevalence of mild retardation (usually considered to be due to poor stimulation and diet) has been steadily declining for decades, scientific productivity has risen greatly, and players in various intellectual games have been reaching high performance levels at earlier and earlier ages.
9. However, the data are all correlational. All the above trends have explanations other than rising intelligence. The issue probably will only be settled when there is a direct physiological measure of g, which may be developed when the human genome project identifies all the genes for intelligence, what they do and how they interact with environmental factors. All sorts of other interesting questions about intelligence can also then be settled.
10. Third, it is still controversial whether the rising prevalence of myopia is not just due to increased close work. So many children today spend almost all their time within four walls, their eyes glued closely to a video screen, or deep into books studying, especially in many Asian nations with their enormous pressure to succeed in the education system. Anecdotal reports from teachers say that many children have grown up within walls staring at video screens, and have no idea how to play on a playground. They need to be instructed. This pillar also needs more research.
11. The target article and additional research on various other long term population trends raise other interesting issues. It is now well established how plastic the developing brain is, and that very complex interactions go on between genes and various environmental factors during development. Now, the human environment has been changing radically in many ways over the 20th Century. For example, the pace of life is accelerating, life gets ever more complex, life gets more sedentary, family size is decreasing, divorce rates are increasing, more and more households consist of just one person, and the widespread entry of women into the workforce means many children grow up in childcare (Hoffman & Youngblade, 1999). Given the interesting, long- term social experiments that humanity has been conducting, especially in the last few decades, one interesting question, well-researched in some instances, is just what effects these are having.
12. Some trends are well known. The increase in height of about 7cm from 1945, usually put down to better nutrition and health, is well known. Also known is an increase in weight, partly put down to better nutrition but also due to an increasingly sedentary lifestyle. The massive amount of stimulation and rapid pace of life that children grow up with apparently has shortened their attention spans, made them entertainment junkies, and lessened their motivation for school work (Steinberg, 1996). As mentioned, children also seem to engage in play less. Play is crucial to normal development and again the long term effects are of some concern. In China, the one-child policy instituted in the late 1970's evidently has produced a generation with a characteristic type of personality; self-centered, intolerant of frustration, and used to much attention and indulgence (Rosenberg & Jin, 1996).
13. Many more long-term trends may be going on and the Storfer target article suggests more researchers could try to determine what these might be. The target article also may encourage scientists to look for interactions between these variables. It is interesting that some trends may be closely linked.
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Storfer, M. (2000) Precis of "Brain size, intelligence and myopia" PSYCOLOQUY 11(083) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/2000.volume.11/ psyc.00.11.083.brain-intelligence.1.storfer http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?11.083
Storfer, M. (1999) Myopia, intelligence and expanding human neocortex: Behavioral influences and evolutionary implications. International Journal of Neuroscience 98(3-4): 153-276. http://www.gbhap-us.com/IJN/storfer/top.htm
Wheeler, L.R. (1942). A comparative study of the intelligence of East Tennessee mountain children. Journal of Educational Psychology, 33, 321-324.