Prenatal androgen exposure and children's aggressive behavior and activity level

Some human behaviors, including aggression and activity level, differ on average for males and females. Here we report findings from two studies investigating possible relations between prenatal androgen and children's aggression and activity level. For study 1, aggression and activity level scores for 43 girls and 38 boys, aged 4 to 11 years, with congenital adrenal hyperplasia (CAH, a genetic condition causing increased adrenal androgen production beginning prenatally) were compared to those of similarly-aged, unaffected relatives (41 girls, 31 boys). Girls with CAH scored higher on aggression than unaffected girls, d = 0.69, and unaffected boys scored higher on activity level than unaffected girls, d = 0.50. No other group differences were significant. For study 2, the relationship of amniotic fluid testosterone to aggression and activity level was investigated in typically-developing children (48 girls, 44 boys), aged 3 to 5 years. Boys scored higher than girls on aggression, d = 0.41, and activity level, d = 0.50. However, amniotic fluid testosterone was not a significant predictor of aggression or activity level for either sex. The results of the two studies provide some support for an influence of prenatal androgen exposure on children's aggressive behavior, but not activity level. The within-sex variation in amniotic fluid testosterone may not be sufficient to allow reliable assessment of relations to aggression or activity level.     

Prenatal hormones and childhood sex segregation: playmate and play style preferences in girls with congenital adrenal hyperplasia

We investigated playmate and play style preference in children with congenital adrenal hyperplasia (CAH) (26 females, 31 males) and their unaffected siblings (26 females, 17 males) using the Playmate and Play Style Preferences Structured Interview (PPPSI). Both unaffected boys and girls preferred same-sex playmates and sex-typical play styles. In the conflict condition where children chose between a same-sex playmate engaged in an other-sex activity or an other-sex playmate engaged in a same-sex activity, boys (both CAH and unaffected brothers) almost exclusively chose playmates based on the preferred play style of the playmate as opposed to the preferred gender label of the playmate. By contrast, unaffected girls used play style and gender label about equally when choosing playmates. Girls with CAH showed a pattern similar to that of boys: their playmate selections were more masculine than unaffected girls, they preferred a boy-typical play style and, in the conflict condition, chose playmates engaged in a masculine activity. These findings suggest that prenatal androgen exposure contributes to sex differences in playmate selection observed in typically developing children and that, among boys and girls exposed to high levels of androgens prenatally, play style preferences drive sex segregation in play.     

Effects of early androgens on sex-typed activities and interests in adolescents with congenital adrenal hyperplasia

The goal of this study was to examine the relation of early androgen exposure to sex-typed activities and interests in adolescence. Participants aged 9-19 years included 24 girls and 18 boys with congenital adrenal hyperplasia (CAH) and 16 unaffected sisters and 24 unaffected brothers who served as controls. Using standardized questionnaires, adolescents reported on their participation in sex-typed activities and interest in sex-typed occupations, and parents reported on the adolescents' activities. As hypothesized, girls with CAH showed sex-atypical preferences: increased interest in male-typical activities and careers and reduced interest in female-typical activities and careers compared to the unexposed control girls. These results extend findings of sex-atypical play in young girls with CAH and suggest that the sex-atypical activities and interests of females with CAH reflect direct effects of androgens on the developing brain rather than social responses to virilized genitalia. These results also suggest that population sex differences in activities and interests arise in part from sex differences in early androgens.     

Sex differences in children's free drawings: a study on girls with congenital adrenal hyperplasia

Sex differences are recognized in children's free drawings with respect to motifs, colors, figure compositions, and expression. Boys tend to draw mobile objects and mechanical objects with dark or cold colors and often use bird's-eye-view composition when they draw pictures, whereas girls like to draw human motifs (especially girls and women), flowers, and butterflies with light and warm colors and tend to arrange motifs in a row on the ground. Analyses were made on the drawings of girls with congenital adrenal hyperplasia (CAH) and unaffected boys and girls, using masculine and feminine indexes. Sex difference in masculine and feminine indexes was clear in the drawings by unaffected boys and girls. Their drawings do not or mostly do not contain characteristics typical of the opposite sex. Compared with those of unaffected girls, the pictures of CAH girls more strongly showed masculine characteristics. The feminine index for the pictures of CAH girls was significantly lower than that for unaffected girls, while the masculine index for CAH girls was significantly higher than that for unaffected girls. Furthermore, the masculine index for CAH girls was not significantly different from that of unaffected boys. These results suggest that androgen exposure during fetal life may contribute to shaping masculine characteristics in children's free drawings.     

Gender role behavior in children with XY karyotype and disorders of sex development

Children exhibit gender-typical preferences in play, toys, activities and interests, and playmates. Several studies suggest that high concentrations of pre- and postnatal androgens contribute to male-typical behavior development, whereas female-typical behavior develops in the absence of high androgens levels. This study aims to explore the consequences of hypoandrogenization on gender-typical behavior in children who have an XY karyotype and disorder of sex development (DSD). Participants included 33 children (ages 2-12 years) with an XY karyotype and DSD; 21 reared as girls and 12 reared as boys. Children's preferred activities and interests and playmate preferences were assessed with parent report questionnaires, a structured free-play task, and choice of a toy to keep as a gift. Participant's responses were compared to those of children recruited in a pre-school and elementary school survey (N=166). In this study, the degree of hypoandrogenization as indicated by genital stage and diagnosis showed a significant relationship to nearly all of the gender-related behaviors assessed, supporting the hypothesis that masculinization of gender role behavior is a function of prenatal androgen exposure. Despite the fact that children with partial androgen effects reared as girls showed increased "boyish" behaviors, they did not show increased signs of gender identity confusion or instability on a group level. We conclude that androgen exposure plays a decisive role in the development of gender-typical behavior in children with XY karyotype and DSD conditions.     

A Latent Class Analysis of Bullies,Victims and Aggressive Victims in Chinese Adolescence: Relations with Social and School Adjustments

This study used the latent class analysis (LCA) to identify and classify Chinese adolescent children''s aggressive behaviors. It was found that (1) Adolescent children could be divided into four categories: general children, aggressive children, victimized children and aggressive victimized children. (2) There were significant gender differences among the aggressive victimized children, the aggressive children and the general children. Specifically, aggressive victimized children and aggressive children had greater probabilities of being boys; victimized children had equal probabilities of being boys or girls. (3) Significant differences in loneliness, depression, anxiety and academic achievement existed among the aggressive victims, the aggressor, the victims and the general children, in which the aggressive victims scored the worst in all questionaires. (4) As protective factors, peer and teacher supports had important influences on children''s aggressive and victimized behaviors. Relative to general children, aggressive victims, aggressive children and victimized children had lower probabilities of receiving peer supports. On the other hand, compared to general children, aggressive victims had lower probabilities of receiving teacher supports; while significant differences in the probability of receiving teacher supports did not exist between aggressive children and victimized children.     

Gendered occupational interests: prenatal androgen effects on psychological orientation to Things versus People

There is considerable interest in understanding women's underrepresentation in science, technology, engineering, and mathematics careers. Career choices have been shown to be driven in part by interests, and gender differences in those interests have generally been considered to result from socialization. We explored the contribution of sex hormones to career-related interests, in particular studying whether prenatal androgens affect interests through psychological orientation to Things versus People. We examined this question in individuals with congenital adrenal hyperplasia (CAH), who have atypical exposure to androgens early in development, and their unaffected siblings (total N = 125 aged 9 to 26 years). Females with CAH had more interest in Things versus People than did unaffected females, and variations among females with CAH reflected variations in their degree of androgen exposure. Results provide strong support for hormonal influences on interest in occupations characterized by working with Things versus People.     

Sex differences in 2D:4D and aggression in children and adolescents from five regions of Russia

The aim of this study was to consider digit ratio (2D:4D: a putative marker of prenatal testosterone and estrogen levels) and aggression in a sample of 1,452 children and adolescents (mean age 13.6 years) from five regions of Russia. The 2D:4D was calculated from direct measurements of the fingers, and aggression scores were obtained from completed Buss and Perry (J Pers Soc Psychol 63 (1992) 452–459) aggression questionnaires. The 2D:4D demonstrated significant sexual dimorphism, with lower 2D:4D in boys in all regions. Physical aggression scores were highest in boys, but verbal aggression, anger and hostility were highest in girls. The highest right hand 2D:4D in boys was found in the most northerly population (Central Russia Region). Our data revealed small, but highly significant negative correlations between right 2D:4D, right–left 2D:4D (D_R‐L) and self‐ratings on physical aggression in boys, but not in girls. These relationships remained after considering Russian ethnics only, and controlling for region. We suggest that the associations may be due to sex differences in prenatal androgen secretion. Am J Phys Anthropol 152:130–139, 2013. © 2013 Wiley Periodicals, Inc.     

Social parameters and urinary testosterone level in male chimpanzees (Pan troglodytes)

Studies investigating relationships between social parameters (such as dominance rank, rates of aggressive and sexual behaviors) and androgen (particularly, testosterone) levels in male primates have yielded inconsistent results. In the present study, we address the relationship between androgens, male dominance rank and rank-associated behaviors in two groups of captive chimpanzees, a species characterized by a pronounced dominance hierarchy between adult males. By combining behavioral observations with urinary testosterone (T) measurements, we found that the differences in T concentrations between males were small and not obviously related to their dominance rank. T levels were not related to the rates of initiated aggression and copulatory behavior, but a significant negative relationship between male T level and the rates of strong aggression received was apparent. Our findings, combined with those of others, suggest that any relationship between dominance rank and T depends upon the extent to which individual rank-associated behaviors (e.g. aggressive/sexual) are themselves related to T.     

Sex matters during adolescence: testosterone-related cortical thickness maturation differs between boys and girls

Age-related changes in cortical thickness have been observed during adolescence, including thinning in frontal and parietal cortices, and thickening in the lateral temporal lobes. Studies have shown sex differences in hormone-related brain maturation when boys and girls are age-matched, however, because girls mature 1-2 years earlier than boys, these sex differences could be confounded by pubertal maturation. To address puberty effects directly, this study assessed sex differences in testosterone-related cortical maturation by studying 85 boys and girls in a narrow age range and matched on sexual maturity. We expected that testosterone-by-sex interactions on cortical thickness would be observed in brain regions known from the animal literature to be high in androgen receptors. We found sex differences in associations between circulating testosterone and thickness in left inferior parietal lobule, middle temporal gyrus, calcarine sulcus, and right lingual gyrus, all regions known to be high in androgen receptors. Visual areas increased with testosterone in boys, but decreased in girls. All other regions were more impacted by testosterone levels in girls than boys. The regional pattern of sex-by-testosterone interactions may have implications for understanding sex differences in behavior and adolescent-onset neuropsychiatric disorders.     

Nature Needs Nurture: The Interaction of Hormonal and Social Influences on the Development of Behavioral Sex Differences in Rhesus Monkeys

Thirty years of research on early social and hormonal environments and their relationship to the expression of behavioral sex differences in rhesus monkeys are reviewed. These studies demonstrate that whether aggressive and submissive behaviors are sexually dimorphic depends primarily on the social and not the hormonal environment. Early rearing environments without mothers or allowing brief periods of peer interaction produced higher levels of male aggression and female submission. Presenting behavior was expressed more by females than males in environments with high male aggressivity and female submissiveness. No sex differences in presenting occurred in low aggressivity environments, unless monkeys were reared isosexually, when males presented more than females. Rough and tumble play and foot-clasp mounting were consistently exhibited more by males than females across all rearing environments studied, but rearing environment affected the degree of the sex difference. When reared isosexually males displayed less, and females more, foot-clasp mounting than when heterosexually reared. No social environment increased the low frequency of female rough and tumble play. Suppressing neonatal androgen in males did not effect any sexually dimorphic behavior. Prenatal androgen administration to genetic females masculinized many aspects of their juvenile behavior, consistently increasing rough and tumble play and foot-clasp mounting across different social environments. Thus the sexually dimorphic behaviors which showed the smallest variability across social contexts were the most profoundly affected by the prenatal hormonal environment. These studies demonstrate that the expression of consistent juvenile behavioral sex differences results from hormonally induced predispositions to engage in specific patterns of juvenile behavior whose expression is shaped by the specific social environment experienced by the developing monkey.     

The genetic architecture of behavioral traits in a spider

The existence of consistent individual differences in behavior has been shown in a number of species, and several studies have found observable sex differences in these behaviors, yet their evolutionary implications remain unclear. Understanding the evolutionary dynamics of behavioral traits requires knowledge of their genetic architectures and whether this architecture differs between the sexes. We conducted a quantitative genetic study in a sexually size‐dimorphic spider, Larinioides sclopetarius, which exhibits sex differences in adult lifestyles. We observed pedigreed spiders for aggression, activity, exploration, and boldness and used animal models to disentangle genetic and environmental influences on these behaviors. We detected trends toward (i) higher additive genetic variances in aggression, activity, and exploration in males than females, and (ii) difference in variances due to common environment/maternal effects, permanent environment and residual variance in aggression and activity with the first two variances being higher in males for both behaviors. We found no sex differences in the amount of genetic and environmental variance in boldness. The mean heritability estimates of aggression, activity, exploration, and boldness range from 0.039 to 0.222 with no sizeable differences between females and males. We note that the credible intervals of the estimates are large, implying a high degree of uncertainty, which disallow a robust conclusion of sex differences in the quantitative genetic estimates. However, the observed estimates suggest that sex differences in the quantitative genetic architecture of the behaviors cannot be ruled out. Notably, the present study suggests that genetic underpinnings of behaviors may differ between sexes and it thus underscores the importance of taking sex differences into account in quantitative genetic studies.     

Sex differences in indirect aggression: Psychological evidence from young adults

Many studies have found differences in the types of aggression used by males and females, at least in children and adolescents. Boys tend to use direct physical or verbal aggression, whereas girls tend to use more indirect forms of aggression that prominently feature gossip. Evolutionary theories of sex differences in indirect aggression propose selection pressures that would have acted on older teenagers and adults. Evidence for sex differences in indirect aggression in adults, however, is equivocal. Virtually all studies of adults have found a sex difference in physical aggression, but most have failed to find sex differences in the use of the more indirect forms of aggression. Almost all of these studies have measured indirect aggression using self-reports of aggressive behavior. We investigated sex differences in the psychology of indirect aggression by exposing young adult women and men to the same aggression-evoking stimulus. As evolutionary models predict, we found that women had a stronger desire than men to aggress indirectly, even after controlling for perceptions of social norms and approval. Future work on both evolutionary and social norm models of indirect aggression is warranted.     

Interactions between behavior and plasma steroids within the scramble mating system of the promiscuous green turtle, Chelonia mydas.

We measured plasma androgen (combined testosterone and 5alpha-dihydrotestosterone) (A) and corticosterone (B) in the promiscuous green turtle (Chelonia mydas) during courtship in the southern Great Barrier Reef. This study examined if reproductive behaviors and intermale aggression induced behavioral androgen and adrenocortical responses in reproductively active male and female green turtles. Associations between reproductive behavior and plasma steroids were investigated in green turtles across the population and within individuals. Levels across a range of both asocial and social behaviors were compared including (a) free swimming behavior; (b) initial courtship interactions; (c) mounted behavior (male and female turtles involved in copulatory activities); (d) intermale aggression (rival males that physically competed with another male turtle or mounted males recipient to these aggressive interactions); and (e) extensive courtship damage (male turtles that had accumulated excessive courtship damage from rival males). Behavioral androgen responses were detected in male turtles, in that plasma A was observed to increase with both attendant and mounted behavior. Male turtles who had been subjected to intermale aggression or who had accumulated severe courtship damage exhibited significantly lower plasma A than their respective controls. No pronounced adrenocortical response was observed after either intermale aggression or accumulation of extensive courtship damage. Female turtles exhibited a significant increase in plasma B during swimming versus mounted behavior, but no change in plasma A. We discuss our results in terms of how scramble polygamy might influence behavioral androgen interactions differently from more typical combative and territorial forms of male polygamy.     

Influence of gender and age in aggressive dream content of Spanish children and adolescents.

This study investigated the aggressive components of the dream content of 120 Spanish children and adolescents of 4 different age groups. The C. S. Hall and R. L. Van de Castle (1966) coding system was used to rate the number of dream characters and aggressions, and the content findings were analyzed via the indicators presented by G. W. Domhoff (1993, 1996, 2003). Results confirm the findings of previous studies of gender and age differences in dream content: Boys tend to have more aggressive dream content, which tends to decrease with age until reaching a pattern similar to the normative group; younger children, especially boys, tend to be victims of aggression more frequently than do older children. In addition, a data analysis procedure involving cumulative scoring of the aggression scale as well as nonparametric statistics yielded significant differences between boys and girls of the youngest group for severity of aggression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Masculinized finger length patterns in human males and females with congenital adrenal hyperplasia

The ratio of the length of the second digit (2D) to the length of the fourth digit (4D) is greater in women than in men. Since androgens are involved in most somatic sex differences and since the sexual dimorphism in 2D:4D is stable from 2 years of age in humans, it was hypothesized that finger length pattern development might be affected by early androgen exposure. Human females with congenital adrenal hyperplasia (CAH) are exposed prenatally to higher than normal levels of adrenal androgens, providing an opportunity to test the effects of early androgen exposure on digit ratios. The 2D:4D was calculated for females with CAH, females without CAH, males with CAH, and males without CAH. Females with CAH had a significantly smaller 2D:4D on the right hand than did females without CAH. Males with CAH had a significantly smaller 2D:4D on the left hand than did males without CAH. A subset of six males with CAH had a significantly smaller 2D:4D on both hands compared with their male relatives without CAH. These results are consistent with the idea that prenatal androgen exposure reduces the 2D:4D and plays a role in the establishment of the sex difference in human finger length patterns. Finger lengths may therefore offer a retrospective marker of perinatal androgen exposure in humans.     

The relationship between violent video games,acculturation, and aggression among Latino adolescents

Multiple factors are involved in the occurrence of aggressive behavior. The purpose of this study was to evaluate the hypotheses that Latino middle school children exposed to higher levels of video game playing will exhibit a higher level of aggression and fighting compared to children exposed to lower levels and that the more acculturated middle school Latino children will play more video games and will prefer more violent video games compared to less acculturated middle school Latino children. This study involved 5,831 students attending eight public schools in Texas. A linear relationship was observed between the time spent playing video games and aggression scores. Higher aggression scores were significantly associated with heavier video playing for boys and girls (p < 0.0001). The more students played video games, the more they fought at school (p < 0.0001). As Latino middle school students were more acculturated, their preference for violent video game playing increased, as well as the amount of time they played video games. Students who reported speaking more Spanish at home and with their friends were less likely to spend large amounts of time playing video games and less likely to prefer violent video games (p < 0.05).     

Working memory performance is reduced in children with congenital adrenal hyperplasia

Individuals with classic congenital adrenal hyperplasia (CAH) experience impaired glucocorticoid production and are treated postnatally with glucocorticoids. Prior research with animals and other human populations indicates that glucocorticoids can influence memory, particularly working memory. We tested the hypothesis that children with CAH would show reduced working memory. Children in the United Kingdom, aged 7–11 years, with classical CAH (31 girls, 26 boys) were compared to their unaffected relatives (30 girls, 20 boys) on a test of working memory, the Digit Span test. Vocabulary was also assessed to measure verbal intelligence for control purposes. Children with CAH showed reduced working memory performance compared to controls, on both components of the Digit Span test: p = .008 for Digit Span Forward, and p = .027 for Digit Span Backward, and on a composite score, p = .004. These differences were of moderate size (d = .53 to .70). Similar differences were also seen in a subset of 23 matched pairs of children with CAH and their relatives (d = .78 to .92). There were no group differences on Vocabulary. Glucocorticoid abnormality, including treatment effects, could be responsible for the reduced Digit Span performance in children with CAH. Other factors related to CAH, such as salt-wasting crises, could also be involved. Additional research is needed to identify the cause of the memory reduction, which will help to determine if more rapid diagnosis or more precise glucocorticoid treatment would help prevent memory reduction. Educational interventions might also be considered for children with CAH.     

Interpreting digit ratio (2D:4D)–behavior correlations: 2D:4D sex difference,stability, and behavioral correlates and their replicability in young children

The popularity of using the ratio of the second to the fourth digit (2D:4D) to study influences of early androgen exposure on human behavior relies, in part, on a report that the ratio is sex-dimorphic and stable from age 2 years (Manning etal., 1998). However, subsequent research has rarely replicated this finding. Moreover, although 2D:4D has been correlated with many behaviors, these correlations are often inconsistent. Young children's 2D:4D–behavior correlations may be more consistent than those of older individuals, because young children have experienced fewer postnatal influences. To evaluate the usefulness of 2D:4D as a biomarker of prenatal androgen exposure in studies of 2D:4D–behavior correlations, we assessed its sex difference, temporal stability, and behavioral correlates over a 6- to 8-month period in 126, 2- to 3-year-old children, providing a rare same-sample replicability test. We found a moderate sex difference on both hands and high temporal stability. However, between-sex overlap and within-sex variability were also large. Only 3 of 24 correlations with sex-typed behaviors—scores on the Preschool Activities Inventory (PSAI), preference for a boy-typical toy, preference for a girl-typical toy, were significant and in the predicted direction, all of which involved the PSAI, partially confirming findings from another study. Correlation coefficients were larger for behaviors that showed larger sex differences. But, as in older samples, the overall pattern showed inconsistency across time, sex, and hand. Therefore, although sex-dimorphic and stable, 2D:4D–behavior correlations are no more consistent for young children than for older samples. Theoretical and methodological implications are discussed.     

Association of Family Environment with Children's Television Viewing and with Low Level of Physical Activity

Objective: This study examined associations between the family environment and children's television (TV) viewing and likelihood of being low‐active. Research Methods and Procedures: In 2001, children were recruited from 19 primary schools in Melbourne, Australia. Parents completed a questionnaire about their child's TV viewing and the family environment. Children also completed a questionnaire and wore an accelerometer for 8 days. Movement counts were used to identify low‐active children (lowest quartile). Data were analyzed in May 2004. Results: The sample consisted of 878 children (mean age = 11.5 ± 0.6 yrs). Multiple logistic regression revealed that socioeconomic status [adjusted odds ratios (AOR) = 0.4 boys], frequency families watched TV together (AOR = 2.0 boys), mothers’ (AOR = 1.8 boys; AOR = 2.5 girls) and fathers’ (AOR = 2.6 boys; AOR = 2.8 girls) TV viewing, and rules prohibiting TV during mealtimes (AOR = 0.6 boys; AOR = 0.6 girls) related to children watching TV ≥2 h/d. Variables associated with low‐level physical activity included self‐reported enjoyment of Internet use (AOR = 1.7 boys) and preference for watching TV (AOR = 2.3 girls), perception that mother uses computer a lot (AOR = 1.9 boys) and likes using the computer (AOR = 0.6 girls), fathers’ reported computer/electronic games use (AOR = 1.7 girls), frequency families used computer together (AOR = 0.4 girls), rules that TV viewing must be supervised (AOR = 1.9 boys; AOR = 0.6 girls), and having pay TV (AOR = 0.6 boys) and electronic games at home (AOR = 2.6 boys). Discussion: These findings suggest that the relationships between the family environment and TV viewing and low‐level activity are complex and that these behaviors are distinct.