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Biosocial Aspects ofMathematics LearningSiv Fischbein aa Department of Educational Research , StockholmInstitute of Education , SwedenPublished online: 07 Jul 2006.

To cite this article: Siv Fischbein (1979) Biosocial Aspects of MathematicsLearning , Scandinavian Journal of Educational Research, 23:1, 1-14, DOI:10.1080/0031383790230101

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Biosocial Aspects of MathematicsLearningl

SIV FISCHBEIN

Department of Educational ResearchStockholm Institute of Education, Sweden

Abstract: Fischbein, Siv 1979. Biosocial Aspects of Mathematics Learning.Scandinavian Journal of Educational Research 23, 1-14. A model for interpretinglongitudinal twin data is presented. Heredity X environment interaction and cor-relation are assumed to vary depending upon type of variable studied and thepermissiveness-restrictedness of environmental factors. Predictions of within-pairsimilarity for MZ and DZ twins on standardized achievement test results in Mathe-matics from grade 3 to 6 are made on the basis of this model. As expected, under thepresence of interactional and correlational effects, MZ twins tend to get moresimilar and DZ twins less similar during a period when they are exposed to the'same' treatment (instruction). A comparison of twins from different social back-grounds shows that the interactional and correlational effects tend to be greatestfor working class children.

INTRODUCTIONIt is generally agreed that there is a large variation among childrenin aptitude and predisposition as well as interest and motivation fordifferent subjects, at the beginning of school. A discussion on theorigin of this variation and on whether one of the aims of schooleducation is to decrease the variation, and if so in what respect, willimmediately arouse more controversy. Pupils in Sweden are exposed,however, to a 'similar' treatment at school (comprehensive educationfor nine years with the same curriculum for everyone and no stream-ing) and it is probably often assumed that the similarity of treatmentwill in some respects at least make the pupils more alike when theyleave school. This assumption could, however, be questioned and willprobably be true only when speaking about basic knowledge thateveryone can learn if given enough time ('mastery learning'). As longas only this basic knowledge is tested, variation will of course decreaseuntil it becomes practically negligible (Bloom 1976).

Depending upon aptitude, predisposition, interest, and motivationfor school work, the learning of this basic knowledge will not consumethe same amount of time for different individuals. This type of in-

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2. SIV FISCHBEIN

formation is also not only acquired in the school situation, but onother occasions as well, which will be more or less frequent for differentindividuals.

In connection with the argumentation presented above, a pertinentquestion will be what causes the variation that every teacher is familiarwith. In certain respects it is evident that biological factors are ofconsiderable importance in causing the variation, for instance con-cerning physical growth, where the difference between the earliest andthe latest maturer can be as large as seven years (Lindgren 1975; Fisch-bein 1977). In other respects it is also obvious that social factors play alarge part in the variation among pupils. Many studies have shownthat most of the children that fail and leave school come from dis-advantaged home environments where motivation for school work isvery low (Emanuelsson 1974).

Differences between individuals cannot, however, be just referredto either biological or social factors, because children develop in aconstant interaction between such factors. Depending upon thecharacteristics studied and environmental circumstances, this inter-action will be different. On the basis of a model designed to study sucheffects, some results from a longitudinal investigation of a Swedishtwin sample will be discussed here.

MATERIALS AND METHODS

In 1964 a longitudinal study of physical and mental growth in twinsand controls of matched age (the SLU-project) started at the Depart-ment of Educational Research at the Stockholm Institute of Education.The twins were collected from the 40 largest cities and towns inSweden and their controls were attending the same classes as thetwins. Originally, the twin sample consisted of 94 pairs of mono-zygotic (MZ) twins, 133 dizygotic (DZ) of the same sex, and 97 boy-girl pairs. There were no separated twin pairs included in the in-vestigation, so all pairs were living in the same home environment andmost of the twins attended the same classes at school.

The twins and their controls were followed from grade three atapproximately 10 years of age to grade nine at approximately 16years of age. Different types of data were collected during this period:

Physical measurements (height and weight, menarche, ratings ofsecondary sex characteristics).

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BIOSOGIAL ASPECTS OF MATHEMATICS LEARNING 3

Ability and achievement test results (differential ability test /DBA/,standardized achievement tests). ^ - ^Self ratings.Ratings by teachers and classmates.Socioeconomic background data (father's occupation and income).

A thorough description of the project has been given by Brucefors(1972). As a measure of school achievement, standardized test resultsin Mathematics in grade 3 and 6 for MZ and DZ twin pairs wereused. These were the only achievement measures collected in theSLU-project on two separate occasions for the twins.

The standardized achievement test in Mathematics consists ingrade 3 of three subtests: mechanical arithmetic, mental arithmetic,and mathematical problem solving. In grade 6, results from five sub-tests were collected: mechanical arithmetic, mental arithmetic, mathe-matical problem solving, geometry and mathematical text. The testswere optional, which means that not all the twins participated. Ingrade 3 approximately 65% of the twins completed test results and ingrade 6 around 75%. A comparison of the total sample (both twinsand controls) which a norm group was made by Fischbein (1976). TheSLU sample showed somewhat higher average test results, which is inaccordance with expectation since the sample was taken from onlyhigh density areas.

The standardized achievement tests have been constructed to equa-lize marks in the Swedish school system. The purpose is therefore todifferentiate between pupils, not to find out what basic knowledgein a subject all, or practically all, pupils have achieved. The test itemsare randomly chosen from essential parts of the curriculum (Anvis-ningar till standardproven/Manual to the standardized achievementtests).

The grouping of children by socioeconomic status was made accord-ing to father's occupational status (Fischbein, op.cit.):

I Employers (mostly university graduates)II Salaried employees (e.g. small owners, administrators)

III Manual workersFor classifying the same-sexed twin pairs a morphological diag-

nosis according to a special schedule was applied. This schedule isbased on earlier investigations of similarity diagnosis in twins (Esse*n-Moller 1941; Norinder 1946; Huse"n 1959). A description of thezygosity classification has been given by Fischbein (op.cit. p. 26).

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SIV FISCHBEIN

Intra-class correlation coefficients were used to make within-paircomparisons for MZ and DZ twins. The coefficients show the magni-tude of within-pair variance relative to between-pair variance. Theformula used is

Vbp + Vwp

(R = intra-class coefficient, Vbp = variance between pairs, Vwp =variance within pairs).

For a more detailed discussion of this method and for a descriptionof the data program used for computing, see Ljung (1966).

A MODEL OF NATURE-NURTURE CONTRIBUTION

A model was constructed in the SLU-project to illustrate, by means oflongitudinal twin data, the dynamic interaction between biologicaland social factors in the study on the development of different charac-teristics (Fischbein 1978a). The statistical model used in earlier twinstudies was an additive one. The assumption made in this model isthat a change in environment will contribute to a comparable changein all genotypes. The interactional model, on the other hand, assumesthat a similar environmental impact may have quite differential effectsdepending upon the genotype (Overton 1973; Lerner 1978; Polonsky1978). Biologically identical individuals like MZ twins, will thereforereact similarly to the same treatment, while biologically non-identicalindividuals will react differently.

Fuller & Thompson (1960) discussed the effects of similar treatmenton within-pair similarity for MZ and DZ twins. They suggested thateither a divergence or a convergence hypothesis can be advocateddepending upon environmental demands. If 'subjects are free toexploit their environment in a variety of fashions they will by chancelight upon quite different modes of adaptation'. In accordance withthis divergence hypothesis, MZ twins will tend to choose the samekind of adaptation and remain concordant, while the opposite willbe true for DZ twins. If, on the other hand, the convergence hypot-hesis is true, 'one specific response is reinforced, other responses willbe extinguished, and all the subjects will converge upon a commonpattern'.

As can be seen from this hypothetical discussion, the existence ofgenotype X environment interaction and correlation will depend

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BIOSOGIAL ASPECTS OF MATHEMATICS LEARNING

both on the kind of variable studied and how much freedom is givento adapt differently to the environment. With a more permissiveenvironment, interactional and correlational effects could be assumedto be larger than with a more restricted environment.

Thus, the intra-pair similarity for MZ and DZ twins can be hypoth-esized to show different trends, during a period when the twins areexposed to similar environments, depending on both the character-istic studied and environmental 'permissiveness-restrictedness'. Themodel illustrated in Figure 1 presents hypothetical intra-class corre-lations for MZ and DZ twins, assuming similar environments, andvarying nature-nurture contribution.

R 3

1.00

0.0

Constant and addiiiveenvironmental effects

t ime axis

Divergence hypothesisI n t e r a c t i o n a l and c o r r e l a -t i ona l e f f e c t s{permissive environment)

R c)

1.00

0.0

MZ

DZ

Convergence hypothesis

(restricted °nvironment)

R d)

1.00

1.0time axis

A variable primari lycontrolled by environ-mental factors

Figure 1. Hypothetical intra-class correlations for MZ and DZ twins assumingsimilar environments, and varying nature-nurture contribution.

• M Z

_ DZ

t i m e a x i s

R b)

1.00

MZ

~ DZ

0.0

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6 SIV FISCHBEIN

Example a) illustrates a variable primarily controlled by geneticfactors where environmental effects are assumed to be constant andadditive. MZ twins, due to their identical inheritance, tend to be moresimilar than DZ twins as long as the twins are exposed to the sameenvironment. No lowering of the intra-class correlations with increasingage is hypothesized.

Example b) illustrates the divergence hypothesis. MZ twins areaffected and react similarly to the same environmental influence,while DZ twins are affected and react differently and thus becomeprogressively less similar. A lowering of the intra-class correlationsfor DZ twins but not for MZ with increasing age is hypothesized.

Example c) illustrates the convergence hypothesis. Due to restrictedenvironmental influences negatively reinforcing genetic differences,DZ twins will become progressively more similar with increasing age.The intra-class correlations for DZ will thus be higher with increasingage and remain constant for MZ twins.

Example d) illustrates a variable primarily controlled by environ-mental factors. Since the identical inheritance of MZ twins does notpredispose them for greater similarity, it will be rather incidental ifthe intra-class correlations for MZ are higher or lower than for DZ.

RESULTS

On the basis of the model described above, hypothetical outcomescould be predicted concerning school achievement for the MZ andDZ twin pairs included in the SLU-study.

Standardized achievement tests in Mathematics

The twin pairs that have attended the same classes at school fromgrade 3 to 6 have been exposed to a similar treatment in the sensethat they have had the same teacher and received the same instruction.Standardized achievement test results in Mathematics can be used tostudy the effects of that treatment. As has been mentioned before,these tests were constructed to differentiate between pupils and notto measure 'basic knowledge'. This fact, in addition to the expectedvariation in experiencing school instruction, will lead to the conclusionthat interactional and correlational effects probably contribute a lotto the variation in achievement measured by standardized test results.This should be evident for both boys and girls. The following hypoth-eses can therefore be made:

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BIOSOGIAL ASPECTS OF MATHEMATICS LEARNING 7

Monozygotic twins (MZ) will be more or constantly similar fortest results from grade 3 to 6.Dizygotic twins (DZ) will be progressively less similar in test resultsfrom grade 3 to 6.The divergent trend will be present for both boys and girls.Table I shows the results of the analysis of variance of the total

score on the Mathematics tests in grade 3 and 6 for MZ and DZ twinsseparated for sex. (Raw scores have been transformed to a scale withX = 50 and SD = 10.)

Table I. Analysis of variance of Mathematics test results for twin pairs in grades 3and 6.

N

vbPV«pFR

NvbPVwpFR

BoysMZ

1995.2216.745.69

.70

3294.1112.897.30

.76

DZGrade 3

37119.6628.464.20

.62

Grade 64 5 •

141.8541.63

3.41.55

GirlsMZ

2768.1620.443.33.54

3252.26 •

9.705.39

.69

DZ

35119.0331.213.81

.58

48 : .98.0428.88

3.40.55

As can be seen from Table I, the within-pair variance increasesrelative to the between-pair variance for the DZ twins from grade 3to 6. The opposite trend is evident for the MZ twins. This can also beseen from the F-ratios decreasing for DZ twins and increasing for MZ.The results thus tend to confirm the hypothesis that MZ twins becomemore concordant and DZ twins less concordant when exposed to similartreatment in school. This conclusion is valid for both boys and girls.

Figure 2 illustrates the within-pair similarity for MZ and DZ twinboys and twin girls by means of the intra-class correlations presentedin Table I.

This figure also shows that MZ twins, attending the same classes,become more concordant in Mathematics test results from grade 3 to 6.The DZ pairs, on the other hand, become progressively less concordant.The trend is the same for both boys and girls, although the latter

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SIV FISGHBEIN

uu

80

60

40

20

^_________—— Mz

- MZ

~~—-^~lS DZZ-^^=^— DZ

1 1

Boys

Girls

3 6 Grade

Figure 2» Intra-class correlations in Mathematics for twin boys and twin girls ingrades 3 and 6.

generally tend to have lower correlations. This could possibly becaused by the Mathematics test being somewhat more difficult forthe twin girls. This would lead to more unexplained variance such asguessing, etc. (Fischbein 1976).

Socioeconomic differencesAccording to expectation, the results from the SLU-project also

show that there are average differences in test results for differentsocioeconomic groups (p. 3) so that group I has a higher average thangroup II that is higher than group III (Fischbein 1978b). It wouldtherefore be of interest to study more thoroughly the role played bybiological and social factors in causing such differences. Are theinteractional and correlational effects found for results on the Mathe-matics tests (e.g. that individuals with varying aptitude and predis-position are affected and react differently to similar treatment) of thesame magnitude in different socioeconomic groups? It is difficult topredict the outcome of this analysis, but a plausible assumption would

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BIOSOCIAL ASPECTS OF MATHEMATICS LEARNING 9

be that the experience of school instruction is more similar for childrenfrom group I and II compared to group III. The variation caused bythe above-mentioned effects could therefore be expected to be less inhigher socioeconomic strata. Bernstein (1975) and others have, forinstance, shown that the instruction offered at school is better suitedfor pupils from intellectually more stimulating home environments.

Table II gives the analysis of variance result in grade 3 and 6 forgroup I and II together and group III separately. The reason formaking this grouping is that group I consists of too few twin pairs tomake a comparison worth while.

Table II. Analysis of variance of Mathematics test results for twin pairs fromdifferent socioeconomic background.

NvbPVwpFR

NvbPVwpFR

Group IMZ

2886.1321.773.96

.60

4297.5411.318.63

.79

+ 11DZ

Grade 345

139.3130.294.60

.64

Grade 655

131.0232.404.04

.60

GroupMZ

1874.8114.475.17

.68

2357.729.246.25

.72

IIIDZ

26107.2029.62

3.62.57

3889.2147.90

1.86.30

For MZ twins in group I + II the within-pair variance decreasesrelative to the between-pair variance from grade 3 to 6 (the F-ratiorises). For the DZ pairs the variance estimates are practically constant.In group III, on the other hand, there is a change for the DZ twins.They tend to show larger within-pair variance relative to between-pair variance from grade 3 to 6. For the MZ pairs in group III thetrend is the same as for group I + II.

The intra-class correlations presented in Table II are illustrated inFigure 3 for group I + II and for group III separately.

This figure shows very clearly that the decrease in within-pairsimilarity for DZ twins from grade 3 to 6, demonstrated for the totaltwin group, can be referred to children from group III. For MZtwins mainly children from group I + II show a rise in within-pairsimilarity over time.

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10 SIV FISCHBEIN

R

8 0 ••

60 ••

40 ..

2.0 • Group I + 11

Group I I I

3 6 Grade

Figure 3. Intra-class correlations in Mathematics for twin pairs from differentsocioeconomic background.

Unfortunately it has not been possible to make the analysis for eachsex separately since the number of pairs is inadequate. The lowcorrelation for MZ twin girls in grade 3 (Figure 2) can, however, besuspected to contribute to the low MZ correlation for group I + II(Figure 3).

DISCUSSIONTo illustrate biological and social aspects of Mathematics learning inschool, results from a longitudinal Swedish twin material have beenpresented and analysed. In earlier twin studies an additive modelwas used for analysing results. The assumption made in this type ofmodel is that a change in environment will lead to a comparablechange in biologically different individuals (DZ) as well as biologi-cally identical individuals (MZ). In the SLU-project an interactionalapproach has been preferred and a model for analysing heredity Xenvironment interaction and correlation on the basis of longitudinaltwin data has been elaborated. This approach leads to the conclusionthat biologically different individuals will be affected differently byand react differently to the same treatment, while biologically identicalindividuals will be affected and react similarly. Interaction thus

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BIOSOCIAL ASPECTS OF MATHEMATICS LEARNING 11

implies a differentiated effect of similar treatment, and correlation differentialreactions to similar treatment, so that biologically different individualscreate for themselves different environments. Depending upon thecharacteristics studied and the room given to individual variations,within-pair similarity in MZ and DZ twins will show different trendsduring a period when the twins are exposed to similar treatment.

In the SLU-project, standardized test results in Mathematics havebeen collected for a twin sample in grade 3 and 6. An interpretationof these results according to the above-mentioned model leads to theconclusion that a similar instruction in school makes biologicallyidentical individuals (MZ) more or constantly alike, while biologicallydifferent individuals (DZ) get less alike in Mathematics knowledge,as measured by the tests. It thus looks as if a similar treatment willlead to different effects and cause different reactions in individuals withvarying aptitude and predisposition. The differences present before treat-ment thus seem to be larger instead of smaller after treatment.

A grouping of the twin sample according to social backgroundshows the interactional and correlational effects to be larger forworking class children, commonly classified as social group 3. It isconcluded that the magnitude of the above-mentioned effects tendsto vary with the characteristics studied and the permissiveness-restrictedness of the environment. Since the same characteristic isstudied for both group I + II and group III, explanations of theresults must be sought in environmental factors discriminating bet-ween different socioeconomic groups:

Instruction affects children from group III more differently be-cause of their larger initial variation.Children from group I + II are living in a more restrictive en-vironment, since more pressure is exericsed by the parents to assurethe acquisition of basic knowledge taught at school.Children from group I + 1 1 are not getting enough stimulationin school to develop their abilities optimally. The environmentcan thus be described as more restrictive for these children bylimiting the variation, referrable to biological differences.It is evident that alternative interpretations of the results can be

suggested. These will not be mutually exclusive, and they probablyall contribute to explain variations in test results for children fromdifferent socioeconomic backgrounds. All the interpretations are basedon the assumption that children from group I + II are living in amore restrictive environment (e.g. that it gives less room for biological

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12 SIV FISCHBEIN

variations) than children from group III, so that interactionaland correlational effects will be less conspicuous for the first-mentionedgroup of children. This assumption is of course only valid for thevariable discussed, that is results on a standardized achievement testin Mathematics. It has to be remembered that with another type ofinstruction or another type of test the result may be quite different.A test could be constructed, for instance, measuring such elementaryknowledge that there will be no variation at all, at least not forchildren from group I + II. It would then not be meaningful todiscuss causes of a practically non-existing variation.

The fact remains, however, that with the differentiated measure ofachievement used here, interactional and correlational effects will beof great importance. These will also be especially evident for childrenfrom environments characterized by other aspirations and expecta-tions than the ones presented in school. Basically this means thatbiological differences will have a considerable impact, since they willdetermine the effect of the influences to which the children areexposed, and also how they will react to this exposure.

It is of course a controversial issue how to handle the large variationbetween individuals in aptitude, predisposition, interest, and motiv-ation that exists in school, irrespective of the role played by biologicaland social factors in creating these differences. Generally it could,however, be argued that school systems in different societies tend toemphasize common societal goals. One of the objectives of the schoolis therefore to implant in the young generation a common frame ofreference and in this respect to decrease variation. In Sweden thisgoal is reflected in a comprehensive primary school with the samecurriculum for all children. The aim is to expose all pupils to similartreatment, even if words like 'individualization' and 'need orientation'of instruction are used in the curriculum (Forslag till forandring avgrundskolans laroplan/Proposition for a change of the curriculum ofthe comprehensive school/; Gustafsson 1977). If such intentions toimplant a common frame of reference fail because this instruction isexperienced differently by biologically different individuals, thequestion arises what can be done about it.

On the basis of the results presented here different strategies can bediscussed. Two possible courses could be chosen:

Through differential treatment make individuals more alike (a realindividualization).

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BIOSOGIAL ASPECTS OF MATHEMATICS LEARNING 13

Through societal pressures guarantee the acquisition of basicknowledge (different kinds of control systems).

These suggestions are not mutually exclusive. They can very wellbe practised at the same time. What is interesting to observe is, how-ever, that through the manipulation of environmental factors thevariation referrable to the interaction of biological and social influ-ences in school can be increased or decreased respectively. Existingbiological differences are thus neither static nor unchangeable, andtheir role will be defined by the environmental circumstances inwhich individuals exist and which they themselves create.

Changes in a school system therefore must take into considerationwhich effects different alternative solutions to existing problems willhave on the variation among individuals and if these are to be pre-ferred or not. In the school debate, such considerations have not beenprevalent and this discussion can therefore be seen more as an attemptto actualize the problems than to present final solutions.

REFERENCES

Anvisningar till standardproven. 1965 and 1967. Manual to the StandardizedAchievement Tests. The National Board of Education. The Section for TestConstruction. Stockholm.

Bernstein, B. 1975. Class and pedagogies: Visible and invisible. Educational Studies 1,23-41.

Bloom, B. S. 1976. Human Characteristics andSchool Learning. New York: McGraw Hill.Brucefors, A. 1972. SLU-projektet 1964-1971. The SLU-Project 1964-1971. Report

no. 66 from the Department of Educational Research, Stockholm Instituteof Education.

Emanuelsson, I. 1974. Utbildningshandikapp i langtidsperspektiv. EducationalDisadvantages in a Lifelong Perspective. Unpublished doctoral thesis,Department of Educational Research, Stockholm Institute of Education.

Essen-Moller, E. 1941. Empirische Ahnlichkeitsdiagnose bei Zwillingen. Hereditas 27,1-50.

Fischbein, S. 1976. Att vara tvilling. Being a Twin. Report no. 2 from the Depart-ment of Educational Research, Stockholm School of Education.

Fischbein, S. 1977. Onset of puberty in MZ and DZ twins. Ada Geneticae Medicaeet Gemellologiae 26, 151-158.

Fischbein, S. 1978a. Heredity-environment interaction in the development of twins.International Journal of Behavioral Development 1, 000-000.

Fischbein, S. 1978b. School achievement and test results for twins and singletons inrelation to socii.l background. In W. E. Nance (Ed.), Twin Research: Psycho-logy and Methodology. Progress in Clinical and Biological Research, Vol. 24 A,101-109. New York: Alan R. Liss, Inc.

Fuller, J. L. & Thompson, W. R. 1960. Behavior Genetics. New York: John Wiley.

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] at

16:

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Forslag till forandring av grundskolans laroplan. 1978. Proposition for a Change ofthe Curriculum of the Swedish Comprehensive School. The National Boardof Education. Liber Educational Publishing Company.

Gustafsson, C. 1977. Classroom Interaction: A Study of Pedagogical Roles in the Teach-ing Process. Stockholm:'Liber.

Huse"n, T. 1959. Psychological Twin Research. Stockholm: Almqvist & Wiksell.Lerner, R. M. 1978. Nature, nurture and dynamic interactionism. Human Develop-

ment 21, 1-20.Lindgren, G. 1975. Pubertet och psykosocial status I. Puberty and Psychosocial

Status I. Physical Development and Maturity During Puberty - DifferentGrowth Patterns. Report no. 4 from the Department of Educational Rese-arch, Stockholm Institute of Education.

Ljung, B.-O. 1966. Intraklasskorrelation.Intra-Class Correlation. An ADB Program.Report no. 16 from the Department of Educational Research, StockholmInstitute of Education.

Norinder, Y. 1946. Twin Differences in Writing Performance. A Study of Heredity andSchool Training. Lund: Hakan Ohlsson.

Overton, W. F. 1973. On the assumptive base of the nature-nurture controversy:additive versus interactive conceptions. Human Development 16, 74-89.

Polonsky, V. M. 1978. Metodologisk aspekt pa det biologiska och sociala i peda-gogiken. Methodological aspect on the biological and social in Education.(Translated from the Russian language by M. Wroblewski). SovjetskqjaPiedagogika 1, 69-76.

NOTE1 This article is based on a paper presented at the NFPF-Congress (Nordic

Association for Educational Research) 19-22 October 1978 in Aalborg.

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