Twins: Mental development in the preschool years.

Wilson, Robert R.

doi:10.1037/h0036596

Cited by 60 publications

(34 citation statements)

References 18 publications

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“…Zygosity of the twins is determined by bloodtyping obtained when the twins are about 3 years old. A description of the longitudinal study and characteristics of the twins and their families may be found elsewhere [9].…”

Section: Subjectsmentioning

confidence: 99%

Appraisal of Parental Bias in Twin Studies.Ascribed Zygosity and IQ Differences in Twins

Matheny

1979

Acta genet. med. gemellol.: twin res.

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A criticism of twin studies has been that the difference between the behavioral similarities of identical and fraternal twins is largely created by parental influences based on their perception of the twins' zygosity. This issue is examined for differences in the IQ scores found within pairs classified by parents and bloodtyping. The systematic differences in IQ scores could be attributed to zygosity classified by bloodtyping rather than by parental belief. The available evidence indicates that the twin method is still appropriate for human behavior genetics.

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Section: Subjectsmentioning

confidence: 99%

Appraisal of Parental Bias in Twin Studies.Ascribed Zygosity and IQ Differences in Twins

Matheny

1979

Acta genet. med. gemellol.: twin res.

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“…9,10,[17][18][19][20] Because these studi es show that tw i ns recover any defi ci ts i n i ntel l ectual performance by 6-8 years of age, 18-20 the compari son of tw i ns and si ngl etons at ages bel ow 8 years does not provi de a good i ndi cati on of adul t tw i n-si ngl eton di fferences. To the best of our know ledge studi es compari ng the IQ of adul t tw i ns and geneti cal l y rel ated si ngl etons have not yet been conducted.…”

Section: Introductionmentioning

confidence: 99%

Twin–singleton differences in intelligence?

Posthuma¹,

Geus²,

Bleichrodt

et al. 2000

twin res

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The tw i n method has been cr i ti ci sed for i ts al l eged non-gener al i sability. When population parameters of intellectual abilities are estimated from a twin sample, critics point to the twinsi ngl eton di ffer ences i n i ntr auter i ne and fami l y envi r onments. These di ffer ences ar e suggested to l ead to subopti mal cogni ti ve devel opment i n tw i ns. A l though pr evi ous studi es have r epor ted tw i nsi ngl eton di ffer ences i n i ntel l i gence, these studi es had tw o major dr aw back s: they tested young tw i ns, and tw i ns w er e compar ed w i th (geneti cal l y) unr el ated si ngl etons. To test accur atel y w hether tw i n-si ngl eton di ffer ences i n i ntel l i gence exi st, a gr oup of adul t tw i ns and thei r non-tw i n siblings were administered the Dutch WAIS-III. The group was large enough to detect twinsingleton differences of magnitudes reported in earlier investigations. The data were analysed using maximum likelihood model fitting. No evidence of differences between adult twins and their non-tw i n si bl i ngs on cogni ti ve per for mance w as found. I t i s concl uded that tw i n studi es pr ovi de reliable estimates of heritabilities of intellectual abilities which can be generalised to the singleton popul ati on. Twin Research (2000) 3, 83-87.

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“…The analysis of variance method described by Wilson (1968Wilson ( , 1974 was also applied to the SLU growth data. An intra-class correlation coefficient for profile contour was computed for the MZ and DZ twin pairs for height and weight.…”

Section: Methodsmentioning

confidence: 99%

“…Wilson (1968Wilson ( , 1974, for instance, compared age-to-age changes for monozygotic (MZ) and dizygotic (DZ) twin pairs by means of an analysis of variance modified for use with twin data. The results were presented as profile correlations for MZ and DZ pairs.…”

Section: Introductionmentioning

confidence: 99%

Profile comparisons of physical growth for monozygotic and dizygotic twin pairs

Fischbein¹,

Nordqvist²

1978

Annals of Human Biology

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Three different methods of analysing similarity of physical growth curves within MZ and DZ twin pairs are compared. The concordance of the curves for each pair can be measured by either a multiple regression coefficient (R2) or the square root of the sum of squared differences between corresponding deviation points (D). The latter seems to be a more appropriate measure of profile contour similarity, mainly because the distance between curves is allowed for. An intra-class correlation based on a longitudinal analysis of variance seems to be a useful measure of average profile similarity for comparing groups of individuals. The distributions of the D measures, calculated for all MZ and DZ twin pairs, show MZ pairs to have significantly smaller D-values for both height and weight, on average, than DZ pairs. The intra-class correlations also show a higher concordance in developmental profile for MZ in comparison to DZ.

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Twins: Mental development in the preschool years.

Cited by 60 publications

References 18 publications

Appraisal of Parental Bias in Twin Studies.Ascribed Zygosity and IQ Differences in Twins

Appraisal of Parental Bias in Twin Studies.Ascribed Zygosity and IQ Differences in Twins

Twin–singleton differences in intelligence?

Profile comparisons of physical growth for monozygotic and dizygotic twin pairs

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