Pullmann Allik Lynn JBiosocSci2004

8/11/2019 Pullmann Allik Lynn JBiosocSci2004

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J. biosoc. Sci. 36, 735740 2004 Cambridge U niversity PressDOI:10.1017/S0021932003006503

T H E G R OWT H OF I Q A M ON G EST ON I A N

SC H O OL C H I L D R E N F R O M A G E S 7 T O 19

HELLE PULLMANN*, JRI ALLIK * RICHARD LY NN

*The Estonian Centre of Behavioral and Health Sciences, Department of Psychology,

University of Tartu, Estonia andUniversity of Ulster, Coleraine, Northern Ireland

Summary. The Standard Progressive M atrices test was standardized inEstonia on a representative sample of 4874 schoolchildren aged from 7 to 19years. When the IQ of Estonian children was expressed in relation to Britishand Icelandic norms, both demonstrated a similar sigmoid relationship. Theyoungest Estonian group scored higher than the British and Icelandic norms:after first grade, the score fell below 100 and remained lower until age 12, andafter that age it increased above the mean level of these two comparisoncountries. The difference between the junior school children and thesecondary school children may be due to schooling, sampling error ordifferent trajectories of intellectual maturation in different populations.

Systematic diff

erences in the growth pattern suggest that the development ofintellectual capacities proceeds at different rates and the maturation processcan take longer in some populations than in others.

Introduction

Data have recently been published for a standardization of the Standard ProgressiveM atrices test in Estonia for adolescents aged 1219 years, and the mean I Q of thissample has been estimated to be 1002 in relation to a British mean of 100 (Lynnet al., 2002). In the current study the Progressive M atrices test was administered to

a sample of Estonian schoolchildren aged 711 years, and it was found that onaverage their IQ was slightly below the British norm, provided that 1979 Britishnorms were corrected for expected secular increase. In order to explain thisdiscrepancy, this study scrutinizes the development trajectory of the IQ of Estonianschoolchildren through the whole age range, from 7 to 19 years.

One of the main components of Piagets (1963) theory of intellectual developmentis that children learn certain things at certain times and it is impossible to skipparticular stages of development. M ost textbooks seem to accept, implicitly at least,that the process of intellectual maturation is uniform across different cultures andfollows thesame relatively fixed course through thestages of intellectual development.

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This uniformity of intellectual development is assumed, not experimentally demon-strated. There is considerable evidence that mean intelligence levels vary substantiallyacross regions and populations (Lynn & Vanhanen, 2002). It is also possible thatchildren in two countries may reach an approximately identical ultimate level ofintelligence through different trajectories of growth. For instance, it is likely that the

periods of most rapid growth are not exactly synchronized and can happen at slightlydifferent moments of chronological age. In this study evidence is provided that thespeed of intellectual development may indeed be different in different populations.

Methods

In 20002001 the Standard Progressive M atrices test was standardized in Estonia ona sample of 4874 schoolchildren aged from 7 to 19 years. Data for 12-year-olds andolder were reported in L ynn et al. (2002), except those for 313 adolescents, which werecollected later. The sample was drawn from 45geographically representative schools

from all of the fifteen Estonian counties (maakond), including the capital city ofTallinn, smaller cities (e.g. Tartu), small towns and rural areas and constitutes 83%of all Estonian schools. The sample contained approximately equal numbers of boys(n=2349) and girls (n=2525). Thechildren tested were in thefirst four grades, the6thand the 8th grades of basic school (phikool) and in the 10th and 12th grades of thesecondary school or gymnasium. M ost students continue in secondary schools orgymnasiums, and only 12% attend vocational schools. In each grade approximately3% of all Estonian children who were born in that particular year were tested.Children in Estonia who attain 7 years of age by 1 October of the current year areobliged to start school. Normally the duration of studies in basic school is nine years.However, this may be prolonged if a student is obliged to repeat some grades. Thus,an individual curriculum may beshorter or longer than the norm. As a result, the ageof students in one grade may differ by 23 years. For more details of the testadministration see Raven (1981).

Estonian data are compared with British and Icelandic norms. A description ofthe test and British norms for children aged 6Y to 15Y years (n=3256) is given byRaven (1981, 2000). I celandic norms for 6Yto 16-year-olds (n=550) are given by Pindet al. (2003).

Results

The results are presented in Table 1. Columns 14give the ages of the children, themean scores, the standard deviations on the test for each of 25 age groups from 7 to19 years, and the numbers of children in each age group. Column 5gives the 1979British 50 percentile norms given by Raven (1981, 2000), and column 6gives the 2000Icelandic means given by Pind et al. (2003).

In order to compare growth rates of intelligence in different countries Estonianmean scores need to beexpressed in relation to British and Icelandic norms. However,before comparing Estonian and British data, an adjustment needs to be made for thesecular increase in IQ. The British norms were collected in 1979, more than 20 yearsearlier than in Estonia. The mean British IQ assessed by the Progressive M atrices

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increased by approximately 2 IQ points a decade over theperiod 1938 to 1989 (Lynn& Hampson, 1986). The rate of increase of IQs appears to have declined during thelast two decades of the twentieth century. In the United States the rate of increase ofthe Wechsler IQ was 33 IQ points per decade over the period 19321978 (Flynn,1984), but it fell to 171 over the years 19781995 (Flynn, 1998). I n Denmark therateof secular increase of a non-verbal reasoning test similar to the Progressive M atricestest over the years 198898 was 135 IQ points (Teasdale & Owen, 2000). Theauthorsconsider that the most reasonable assumption is that the same rate of increase hastaken place for the Progressive M atrices in Britain, and therefore that the British IQincreased by 30 IQ points over the period 19792000. To adjust Estonian andIcelandic results to a British IQ of 100 expected in 2001, it is therefore necessary toadd 30 I Q points to the British IQ. Thus, the whole curve was shifted uniformly 3IQ points down. Because Estonian data were collected approximately at the same

Table 1. Data for the Estonian standardization of the Standard Progressive M atrices

Age M ean SD n British 1979a Icelandic 2000b

65 16 226

70 2584 876 43 19 22775 2581 902 48 22 30680 2612 974 248 25 29385 2812 954 189 31 35290 3223 1007 267 33 36295 3296 844 203 36 393100 3667 815 243 38 405105 3652 838 201 39 379110 3911 863 206 40 414115 3962 904 211 41 427120 4246 888 71 41 439

125 4636 678 300 42 454130 4645 642 325 43 456135 4507 833 97 44 450140 4793 786 126 45 461145 4924 642 286 46 467150 4978 684 295 47 478155 4901 639 125 47 488160 5206 578 223 488165 5262 518 357 170 5224 473 193 175 5278 455 86

180 5297 463 245 185 5290 592 210 190 5317 402 76

aBritish 1979: 50th percentile British 1979 norms (Raven, 1981, 2000).bIcelandic 2000: the mean score for Icelandic children (Pind et al., 2003).

The growth of intelligence 737


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time as the I celandic survey there was no need for adjustment. Figure 1 shows the

Ravens scores of Estonian age groups in relation to British and Icelandic means. Itis remarkable that thetwo data sets look very similar. I ndeed, the correlation betweenthese two sets of I Q values is highly significant (r=079,p


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countries that have remarkably similar growth trajectories. There are several possibleexplanations for the difference between the junior school children and the secondaryschool children in Estonia.

First, the difference between the junior and the secondary school children may bedue to schooling. Studies in which children who differ in both chronological age and

schooling are compared, haveshown that schooling is the major factor underlying theincrease of intelligence test scores (Cahan & Cohen, 1989). Theschooling effect on IQ,however, seems to fade out after a few years (Ceci, 1991). Estonian primary schoolchildren start school at age 7, whereas in Britain and I celand children start school at5 and 6 respectively. This relatively late start might be the reason why Estonian7-year-olds are intellectually slightly behind British and Icelandic children of the sameage. In fact the situation is exactly reversed: the Estonian first-graders are slightlyahead of their counterparts but lag behind after the first year of schooling.

Second, the discrepancy between different age groups may be due to samplingerrors. It is possible that some grades contained more gifted or highly motivated

students and some other grades less gifted and less motivated students. Althoughpossible, this type of sampling error is unlikely due to the large number of schoolsand parallel grades from different schools. The regular S-shape shown in F ig. 1 alsoindicates that deviations from the 100 I Q level are systematic, and not due to somerandom sampling error.

Finally, it is likely that the discrepancy between IQ estimates among Estonianprimary and secondary school children may result from different intellectualmaturation trajectories. It seems that junior school children in Estonia initially lagbehind in their intellectual development but catch up with their counterparts inBritain and Iceland when they reach adolescence. L ike physical maturation (Eveleth& Tanner, 1990), the growth of intellectual capacities may be uneven and thematuration process can take a longer time in some populations than in others. Thisdifferent growth rate may be caused by biological factors, schooling or both.Although none of these factors can be automatically excluded, some of the simplestexplanations can be empirically tested. For example, it is unlikely that theapproximately 710 points lower score of Estonian 9-year-old children is caused bytheir slower physical development compared with their British counterparts. On thecontrary, Estonian 9-year-old boys and girls seem to be physically more developedthan British children of the same age. The mean height of Estonian 9-year-old boysand girls is 1354 and 1340 cm respectively (Veldre, 1997), whereas that of British9-year-old boys and girls was 1317 and 1318 respectively (Eveleth & Tanner, 1990,

pp. 227229).Although it is unclear what exactly causes the different intellectual growth rate,

this study provides evidence that there are different trajectories of intellectualmaturation.

Acknowledgments

The authors would like to thank K aia Laidra, Anneli Veisson and Liisa K iik forhelping to collect data. This research was supported by Estonian Science FoundationGrant 4519 and a grant from the Estonian M inistry of Education (0182585).

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