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S Fischbein

Publications and source records attributed to S Fischbein.

26 records · Page 2Linked to original sources
PubMed1978

Profile comparisons of physical growth for monozygotic and dizygotic twin pairs.

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.

Adolescent↗
PubMed1977

Onset of puberty in MX and DZ twins.

A twin study on the significance of genetic factors for the variation in peak height and peak weight velocity, as well as in age at menarche and the development of secondary sex characteristics, is presented. Evidence of a rather strong genetic regulation of the occurrence of puberty was obtained in the analysis. The maximal height or weight gain (in cm/year of kg/year) seems to be, at least in girls, less influenced by genetic factors than the age at which it appears.

Adolescent↗
PubMed1977

Physical capacity in twins.

A comparison of physical capacity, (measured by vital capacity, muscular strength and physical work capacity) in twin boys and controls failed to indicate significant differences. Intrapair correlations showed the MZ twins to be much more similar than the DZ twins in all the capacity measures. The correlations were lower, however, for both MZ and DZ twins for physical work capacity than for the other two capacity variables. When amount of physical exercise during leisure time is kept under control, the DZ twins tend to be more similar for physical work capacity or muscular strength, and the correlations tend to be of the same magnitude for MZ twins. Physical work capacity therefore appears, in this study, to be a more environmentally influenced variable than either vital capacity or muscular strength.

Female↗
PubMed1977

A comparison of growth in twins and singleton controls of matched age followed longitudinally from 10 to 18 years.

A sample of 323 pairs of twins (94 MZ pairs, 133 DZ like-sexed pairs and 97 DZ unlike-sexed pairs born in 1954/55) were studied longitudinally from 10 to 18 years for boys and 10 to 16 years for girls. Height, weight, age at menarche and peak height and weight velocities (PHV and PWV) were studied. No significant differences occurred between twin categories in any two of these varieties, so in each sex the total twin group was compared with a group of matched singleton controls (380 boys and 360 girls). There were very small differences between the twin boys and their controls in height, weight and PWV-age. PHV occurred somewhat earlier in twin boys than in the controls. The height and weight peaks were significantly lower for the twin boys. For twin girls, however, a height and weight deficit was found during puberty and they also matured a little later than their controls according to both PHV, PWV and menarche. The height and weight peaks were also somewhat lower for the twin girls. One reason for the observed sex differences could be a proportionally higher mortality for twin boys, thus an effect of selective survival.

Adolescent↗
PubMed1977

Intra-pair similarity in physical growth of monozygotic and of dizygotic twins during puberty.

The growth of 323 pairs of twins (94 MZ pairs, 133 DZ like-sexed pairs and 97 DZ unlike-sexed pairs) born in 1954/55 was studied longitudinally from 10 to 18 years for boys and 10 to 16 years for girls. Within-pair comparisons for height and weight have been made for MZ twins and DZ like-sexed twins. A significantly higher concordance in height was found for MZ pairs than for DZ pairs during puberty, for both boys and girls. Yearly height increments were also more similar for the MZ pairs, showing that the height spurt occurs more simultaneously for MZ twins in comparison to DZ twins. Height seems to be a strongly genetically regulated variable. The MZ twins also show a high concordance in weight during the whole investigation period. The DZ pairs, however, became progressively less similar in weight. This is most pronounced for the DZ girls, the intra-class correlation for weight decreasing from 0.66 at 10 years to 0.23 at 16 years. This could imply stronger interactional effects for girls than for boys with regard to weight during puberty.

Adolescent↗
PubMedDate not supplied

Intra-pair similarity in IQ of monozygotic and dizygotic male twins at 12 and 18 years of age.

Verbal and inductive test results have been collected for a group of male twins in grade 5 at 12 years of age and at enrollment to military service at 18 years of age. MZ twin pairs tend to get progressively more concordant for both verbal and inductive ability from age 12 to 18. DZ twins, on the other hand, get progressively more concordant for inductive ability, while they tend to get less concordant for verbal ability. The results are interpreted with reference to a model taking heredity-environment interaction into account. The discordant trend found when comparing intra-pair similarity in verbal ability for MZ and DZ twins thus seems to indicate the presence of interactional and correlational effects. For inductive ability, however, the difference between within-pair correlations for MZ and DZ twins tends to be of the same magnitude at both 12 and 18 years of age. Probably this type of test is less differentially influenced by the environments being sampled, at least under present circumstances, when children are not specifically trained to solve the kind of items included in the inductive test. Regression effects for the two tests and possible explanations to the increase from age 12 to 18 in both MZ and DZ within-pair similarity for inductive test scores are discussed.

Adolescent↗
PubMedDate not supplied

Intra-pair similarity in physical growth of opposite-sex twin pairs during puberty.

A comparison has been made of within-pair similarity in physical growth for opposite-sex twin pairs and pairs of unrelated controls attending the same classes as the twins. Height and weight measurements were originally collected for 97 pairs of twins and controls from 10 to 16 years of age for the girls and from 10 to 18 years for the boys. The twins showed significantly smaller within-pair differences than the controls for both height and weight during the whole investigation period. Within-pair correlations for height and weight were negative for the controls and moderately positive for the opposite-sex twins. The weight correlations for the twins were lower than for height from 11 to 14 years of age. At age 15 the height and weight correlations tended to be of the same magnitude due to a drop in within-pair similarity for height at this age. Profile similarity in physical growth has been studied both for each pair individually (D-values) and for the whole group of twins and controls (analysis of variance). Both comparisons showed both the twins and the controls to be very dissimilar in growth profiles during puberty. Onset of puberty was estimated by age at peak height velocity (PHV) and peak weight velocity (PWV). The average within-pair difference for the controls was shown to be a little more than two years and for the twins a little less. The small and non-significant differences between the groups lead to the main conclusion that sex differentiation at puberty exerts a very powerful influence overshadowing the hereditary and environmental similarities existing for the twins.

Adolescent↗