Academic journal article Mankind Quarterly

A Study of Means and Sex Differences on Raven's Standard Progressive Matrices Plus in Yemen

Academic journal article Mankind Quarterly

A Study of Means and Sex Differences on Raven's Standard Progressive Matrices Plus in Yemen

Article excerpt

A research program to collect IQs for all nations in the world was initiated by Lynn (1978) and has been extended in a number of subsequent publications summarized by Lynn and Vanhanen (2012). In these studies national IQs are scaled as "Greenwich IQs," with a contemporaneous British mean of 100 and standard deviation of 15 as the reference.

In their most recent compilation of national IQs Lynn and Vanhanen (2012) give three IQs for Yemen. Two of these were based on studies of 6-11 years olds tested with the Colored Progressive Matrices, which gave British IQs of 85 and 81 (Al-Heeti et al, 1997; Khaleefa and Lynn, 2008a). The third study was based on the assessment of 4th grade school students in math and science in TIMSS in 2007, where the Yemen sample obtained a British IQ of 64.7 (Meisenberg and Lynn, 2011). It is evident that these studies have produced inconsistent results. One of the objectives of this paper is to report new normative data on intelligence in Yemen.

The second objective of this paper is to report normative data on sex differences in intelligence in Yemen. From the early twentieth century up to the present it has been almost invariably asserted that there is no sex difference in general intelligence defined as the IQ obtained from tests like the Progressive Matrices, the Stanford-Binet, the Wechsler, the Cattell Culture Fair and numerous others. In the second decade of the twentieth century this conclusion was advanced by Burt and Moore (1912) and by Terman (1916), who wrote: "the superiority of girls over boys is so slight (on the American standardization sample of the Stanford-Binet test on 4-16 year olds) ... that for practical purposes it would seem negligible." In the second half of the century this conclusion was reaffirmed by Cattell (1971, p. 131), Hutt (1972, p. 88), Maccoby and Jacklin (1974, p. 65), Jensen (1980, p. 360), Eysenck (1981, p. 40), Brody (1992, p.323), Herrnstein and Murray (1994, p. 275), Seligman (1998, p. 72), Geary (1998, p. 310), Butterworth (1999, p. 293), Lubinski (2000, p. 416), Halpern (2000, p. 218), Bartholomew (2004, p. 91), Anderson (2004, p. 829), Dolan et al (2006, p. 194), Hines (2004, p. 103), and finally, in a recent textbook, "females and males score identically on IQ tests" Halpern (2012, p. 233).

This consensus that there is no sex difference in intelligence was broken by Lynn (1994, 1998, 1999), who advanced a developmental theory of sex differences in intelligence that stated that boys and girls mature at different rates both physically and mentally during childhood and adolescence. The theory states that boys and girls mature at about the same rate up to the age of around 7 years; that from the age of 8 years, girls begin a growth spurt in which there is an acceleration of their physical growth in respect of height, weight, brain size and intelligence; the growth rate of girls slows at the ages of 14 and 15, while the growth of boys continues. Lynn's (1994) original formulation of the theory stated that for abstract (nonverbal) reasoning ability, there is no sex difference up to the age of around 8 years; between the age range of around 9 through 12 years, girls have an advantage of approximately 1 IQ point; there is no sex difference at ages of around 13 to 15 years; and at the age of 16 years, boys have a small advantage that increases with age reaching an advantage among adults of around 4 IQ points. These estimates were not derived from data on the Progressive Matrices but from other data and, in the case of adults, from the American standardization samples of the Differential Aptitude Test. In a subsequent compilation of studies, Lynn (1999) proposed that among adults the male advantage on abstract reasoning is approximately 5 IQ points. Lynn's thesis was derived from the findings by Ankney (1992) and Rushton (1992) that men have a larger average brain size than women, even when controlled for body size. The correlation between brain size and intelligence is approximately . …

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