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Biomedical subjects

C N Jacklin

Publications and source records attributed to C N Jacklin.

18 recordsLinked to original sources
PubMed1991

Sex steroids at birth: genetic and environmental variation and covariation.

Three sex-steroids (estradiol, progesterone, & testosterone) were assayed from the umbilical cord blood of 58 same-sex twin pairs in an investigation of the effects of sex, as well as genetic and environmental factors, on neonatal hormone levels. Although significant mean differences were found between boys and girls for both testosterone and progesterone, sex appeared to account for very little of the total variation for any of the hormones. Results showed that genetic influences significantly affected within-sex variation in both estradiol and progesterone levels, while variations in the intrauterine (shared twin) environment accounted primarily for differences in levels of testosterone. Moderate correlations were also found among the three hormones. Multivariate biometrical analyses revealed these relationships to be explained by an underlying general factor of nonshared environmental influences affecting all three hormones. Genetic factors appeared to be specific to each hormone rather than correlated across hormones. These results suggest not only that genes are operating at this early age, but also that maternal and other prenatal factors (e.g., placental effects, uterine position) have a significant role in variations of sex-steroids and possibly on later behaviors.

Animals↗
PubMed1989

Female and male: issues of gender.

Our culture's preoccupation with gender differences is reflected in the importance developmental psychologists have placed on gender-related issues. In this article, three areas of research where gender is or has been a primary focus of research are discussed: measurement of intellectual abilities, biology and behavior, and socialization processes. Policy implications of the research are suggested.

Child↗
PubMed1989

Masculinity and femininity in twin children: genetic and environmental factors.

Genetic and environmental origins of individual differences in masculine and feminine personality attributes were investigated in a sample of 38 monozygotic and 32 dizygotic twin pairs (total N = 140) during pre- and early adolescence. Self-report measures of both masculine and feminine characteristics were obtained for each child using 2 standardized instruments: the Children's Personality Attributes Questionnaire (CPAQ) and the Adolescent Self-Perception Inventory (ASPI). Multivariate biometrical analyses revealed significant genetic influences in all measures, accounting for 20%-48% of the observed variation in each. Environmental influences, which explained the remaining 52%-80% of variance in masculinity and femininity, were apparently specific to each individual and not shared by members of the same twin pair. The results underscore the importance of considering both genetic and environmental factors in gender-role development, particularly in studies of family resemblance.

Adolescent↗
PubMed1988

Neonatal sex-steroid hormones and cognitive abilities at six years.

Five sex-steroid hormones (testosterone, androstenedione, estradiol, estrone, and progesterone) were assayed in umbilical cord blood. Cognitive abilities were assessed as a part of a 6-year follow-up laboratory visit. Four subtests were given: reading, numbers, listening, and spatial ability. There were no significant differences between boys and girls in cognitive ability scores. Higher levels of perinatal androgens (testosterone and androstenedione) were significantly associated with low age-6 spatial ability in girls. Multiple regression analyses revealed a significant proportion of the variance in cognitive abilities in girls could be accounted for by testosterone and androstenedione. No significant predictions were found for boys. The finding of a stable inverse association between sex and effect of hormones on abilities is discussed.

Achievement↗
PubMed1985

Individual differences in mood in early childhood: their relation to gender and neonatal sex steroids.

Predominant mood states were assessed for 104 children via 24-hr mother diaries during the first 2 years of life. Consistent sex differences were found across ages and across cohorts: boys were more often reported to be in a happy/excited mood, girls in a quiet/calm mood. The sexes did not differ in the frequency of negative moods (including crying), however. Scores for happy/excited and quiet/calm mood states were quite stable across the ages sampled: 6, 9, 12, 18, and 26 months. These stabilities were generally greater for boys. Negative moods showed only borderline stability. Relationships between the mood scores and five sex-steroid hormones (progesterone, androstenedione, testosterone, estrone, and estradiol), assayed from umbilical cord blood at the time of the children's birth, were assessed. For boys small, but significant, positive relationships were found between happy/excited moods and androstenedione, estrone, and progesterone. Correlations of opposite sign were found between these hormones and boys' scores for quiet/calm mood. For girls, the correlations were low and insignificant, but generally of opposite sign from those found for boys, and a number of hormones showed significant sex-by-hormone interactions in their relation to children's mood scores. The implication of these findings for the understanding of sex differences is discussed. Also discussed are the problems of interpretation posed by the intercorrelations among hormones when hormone scores are used for prediction of aspects of later development.

Affect↗
PubMed1984

Neonatal sex-steroid hormones and muscular strength of boys and girls in the first three years.

Five sex-steroid hormones were assayed in umbilical cord blood. Strength was assessed in children in three samples at several ages from birth to 33 months. At different ages, different strength measures were taken, viz., at birth, prone head responses; at 3 months, leg strength; from 6 to 33 months, grip strength. Boys had higher average strength scores than girls but the sex differences were small and did not increase or decrease over the age period studied. Across-age strength scores showed a significant relation to androstenedione and a significant interaction of sex and progesterone. Both boys and girls with higher strength scores had lower androstenedione. Girls with high cord blood progesterone showed low strength while boys with high progesterone showed high strength. There were no sex differences in androstenedione or progesterone level. The androstenedione finding did not replicate across samples but the Progesterone X Sex interaction was replicated in all three samples. No relationship was found between strength and other hormones assayed: testosterone, estradiol, and estrone.

Androstenedione↗
PubMed1984

Sex-typing behavior and sex-typing pressure in child/parent interaction.

The sex-typing of children and the sex-typing pressure of parents was investigated during free play in a home visit. There were 30 male and 24 female 45-month-olds observed with their mothers and fathers in separate free-play sessions during which an array of both sex-stereotyped and neutral toys were available. Behavioral observations were recorded for a variety of parent, child, and dyadic behaviors, including initiations of sex-typed play, total sex-typed play, and rough-and-tumble play. Children initiated sex-typed play and played with sex-appropriate toys. Father-child and mother-daughter dyads were more likely to engage in thematic play appropriate to the child's sex, while in mother-son dyads equal amounts of masculine and feminine play occurred. In addition father-son dyads displayed the highest levels of rough-and tumble play and arousal of child by parent. The results suggest that fathers are the discriminating influence on sex-appropriate play.

Child, Preschool↗
PubMed1983

Neonatal sex-steroid hormones and timidity in 6-18-month-old boys and girls.

Five sex-steroid hormones (testosterone, androstenedione, estradiol, estrone, and progesterone) are assayed in umbilical cord blood. Timidity is assessed in home and laboratory observations by reactions to a range of novel toys in children from 6 to 18 months of age. Significant short- (1 week) and long- (several months) term stability in timidity is demonstrated. Girls have higher mean scores on observed timidity than do boys in 2 of the 3 samples tested. An across-age timidity score is computed which shows significant correlations with neonatal progesterone, testosterone, and estradiol for boys, but is not significantly predicted by hormone concentrations in girls.

Androstenedione↗
PubMed1980

Sex differences in aggression: a rejoinder and reprise.

A meta analysis of observational studies of peer-directed aggression by children aged 6 and younger yields a highly significant sex difference. Out of 32 studies, z values reflected higher male aggression in 24, no difference in 8, higher female aggression in none. Furthermore, boys' aggression is most often displayed in the presence of male partners. Evidence is presented that the sex difference is probably not merely an artifact of higher rates of male activity or social interaction. Existing cross-cultural evidence also shows higher rates of male aggression, as does most of the work on free-living primates. Specifically, the 3 observational studies of chimpanzees show considerably more aggression in males. Evidence for a hormonal contribution to male aggression is clear in animals and inconclusive in human beings, although the existing human findings are consistent with such a contribution. Recent evidence on the differential socialization of boys and girls supports our earlier view: that boys do not receive more reinforcement for aggression than girls, and that rates of punishment are also similar once the differential base rates in aggression are taken into account. The role of self-socialization (including choice of same-sex models) is discussed, and the view is expressed that this probably depends upon the development of certain cognitions about sex identity which normally do not develop until a later age than the age at which a consistent sex difference in aggression first appears.

Adolescent↗
PubMed1979

Concentrations of sex hormones in umbilical-cord blood: their relation to sex and birth order of infants.

In 3 groups of human newborns, 5 sex hormones were assayed from samples of umbilical-cord blood, and concentrations were analyzed by the sex and birth order of the infants. The 5 hormones assayed were testosterone, androstenedione, estrone, estradiol, and progesterone. Concentrations of testosterone were significantly greater in males than females. The other 4 hormones did not differ significantly by sex. In both sexes, firstborns had significantly more progesterone and estrogens, with progesterone showing the largest birth-order effects. Among male infants, firstborns had higher concentrations of testosterone. The higher concentrations of progesterone in firstborns of both sexes, and of testosterone in firstborn boys, were found not to be due to length of labor, birth weight, or maternal age. However, they were a function of temporal spacing of childbirths. Later borns who were closely spaced in relation to their next-older siblings had lower concentrations of hormones. The effect of temporal separation was greater on male than female infants for each of the 5 hormones studied. The results are discussed in terms of the possible effects of hormone "depletion" on the psychological development of closely spaced later borns.

Androstenedione↗
PubMedDate not supplied

Neonatal sex-steroid hormones and physical size at four years.

This study investigated the relationships of neonatal sex-steroid hormones to preschool children's size. Two measures of size were considered: a unidimensional measure of height and a weight-for-height ratio. Results showed a significant positive relationship between girls' neonatal progesterone and the weight-for-height ratio at age four. A negative association of this ratio with an estrogen composite measure was also found. High testosterone girls had higher weight-for-height ratios than low testosterone girls. A significant positive association between the estrogen composite and height was found for boys. These findings indicate that neonatal hormone levels are important complements to environmental factors (e.g., nutrition) in predicting later growth.

Androstenedione↗