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Human males and females show average gender/sex differences for certain psychological phenomena. Multiple factors may contribute to these differences, including sex chromosomes, exposure to gonadal hormones, and socialization or learning. This study investigated potential hormonal and socialization/learning influences on gender/sex differences in childhood preferences for color, specifically pink and red vs. blues, and for toys. Children (aged 4 to 11 years) with congenital adrenal hyperplasia (CAH, n=43 girls and 37 boys), marked by elevated prenatal adrenal androgen exposure, and without CAH (n=41 girls and 31 boys) were studied. Prior research indicates girls with CAH are masculinized for certain behaviors, such as toy choices, while boys with CAH generally do not differ from boys without CAH. In the current study, children indicated preferences for stereotyped hues of pink vs. blue as well as two control color pairs. They also indicated their preference between gender/sex-typed toys (doll vs. car) presented in black and white, in gender/sex-congruent colors (pink doll vs. blue car) and in gender/sex-incongruent colors (pink car vs. blue doll). Color findings: control girls preferred stereotyped pink over blue more than boys or girls with CAH did; the latter two groups did not differ in their color preferences. No preference differences occurred for other color pairs. Toy findings: In black/white or gender/sex-congruent colors, boys preferred the car more than control girls or girls with CAH did, while girls with CAH preferred the car more than control girls did. In gender/sex-incongruent colors (pink car vs. blue doll), boys still preferred the car, while girls with CAH showed reduced and control girls showed increased preferences for the pink car compared to the car preferences in black/white. Results support learning theories of color preferences, perhaps also influenced by pre-existing toy preferences which may occur for other reasons, including early androgen exposure. Specifically, girls with CAH may have learned they do not enjoy stereotypical toys for girls, often colored pink, and pink coloring may subsequently diminish their preference for a car. Our results highlight the importance of gonadal hormones and learning in the development of childhood toy and color preferences.

BACKGROUND: Autism is more prevalent in males than in females. Hypotheses related to the extreme male brain theory of autism suggest that heightened androgen exposure during early development contributes to autistic traits. Whilst prior research focused mostly on the prenatal period, the current study tests the influences of androgen exposure during both the prenatal and the early postnatal periods on autistic traits during childhood. METHODS: Anthropometric measures that are putative biomarkers of early androgen exposure were employed. Anogenital distance (AGD) was measured at birth and 3 months of age in boys and girls. Penile length at birth and 3 months of age was also measured in boys. When the children were 9-13 years old, a parent-reported questionnaire (the 10-item children's version of the Autism Spectrum Quotient; AQ-10 Child) was used to assess autistic traits in 97 boys and 110 girls. RESULTS: There were no significant associations between any of the AGD or penile length measures and scores on the AQ-10 Child in boys, girls or the entire sample. CONCLUSIONS: The current study provides the first test of whether early measurements of AGD and/or penile length predict subsequent autistic traits. The current findings do not support a relationship between prenatal or early postnatal androgen exposure and autistic traits. The current study augments prior research showing no consistent relationship between early androgen exposure and autistic traits.

During the first few years of life, girls typically have a larger expressive vocabulary than boys. This sex difference is important since a small vocabulary may predict subsequent language difficulties, which are more prevalent in boys than girls. The masculinizing effects of early androgen exposure on neurobehavioral development are well-documented in nonhuman mammals. The present study conducted the first test of whether early postnatal testosterone concentrations influence sex differences in expressive vocabulary in toddlers. It was found that testosterone measured in saliva samples collected at 1–3 months of age, i.e., during the period called mini-puberty, negatively predicted parent-report expressive vocabulary size at 18–30 months of age in boys and in girls. Testosterone concentrations during mini-puberty also accounted for additional variance in expressive vocabulary after other predictors such as sex, child’s age at vocabulary assessment, and paternal education, were taken into account. Furthermore, testosterone concentrations during mini-puberty mediated the sex difference in expressive vocabulary. These results suggest that testosterone during the early postnatal period contributes to early language development and neurobehavioral sexual differentiation in humans.

The masculinizing effects of prenatal androgens on human neurobehavioral development are well established. Also, the early postnatal surge of androgens in male infants, or mini-puberty, has been well documented and is known to influence physiological development, including penile growth. However, neurobehavioral effects of androgen exposure during mini-puberty are largely unknown. The main aim of the current study was to evaluate possible neurobehavioral consequences of mini-puberty by relating penile growth in the early postnatal period to subsequent behavior. Using multiple linear regression, we demonstrated that penile growth between birth and three months postnatal, concurrent with mini-puberty, significantly predicted increased masculine/decreased feminine behavior assessed using the Pre-school Activities Inventory (PSAI) in 81 healthy boys at 3 to 4years of age. When we controlled for other potential influences on masculine/feminine behavior and/or penile growth, including variance in androgen exposure prenatally and body growth postnally, the predictive value of penile growth in the early postnatal period persisted. More specifically, prenatal androgen exposure, reflected in the measurement of anogenital distance (AGD), and early postnatal androgen exposure, reflected in penile growth from birth to 3months, were significant predictors of increased masculine/decreased feminine behavior, with each accounting for unique variance. Our findings suggest that independent associations of PSAI with AGD at birth and with penile growth during mini-puberty reflect prenatal and early postnatal androgen exposures respectively. Thus, we provide a novel and readily available approach for assessing effects of early androgen exposures, as well as novel evidence that early postnatal aes human neurobehavioral development.

Funder: Cambridge Commonwealth, European and International Trust; Id: http://dx.doi.org/10.13039/501100003343, Funder: Gates Cambridge Trust; Id: http://dx.doi.org/10.13039/501100005370, Funder: School of the Biological Sciences, University of Cambridge; Id: http://dx.doi.org/10.13039/501100000705, Funder: Clare College, University of Cambridge; Id: http://dx.doi.org/10.13039/501100001625, Funder: Smuts Memorial Fund, University of Cambridge; Id: http://dx.doi.org/10.13039/501100000710, Preferences for pink and blue were tested in children aged 4-11 years in three small-scale societies: Shipibo villages in the Peruvian Amazon, kastom villages in the highlands of Tanna Island, Vanuatu, and BaYaka foragers in the northern Republic of Congo; and compared to children from an Australian global city (total N = 232). No sex differences were found in preference for pink in any of the three societies not influenced by global culture (ds - 0.31-0.23), in contrast to a female preference for pink in the global city (d = 1.24). Results suggest that the pairing of female and pink is a cultural phenomenon and is not driven by an essential preference for pink in girls.