Male, Female by David C. Geary;

Author:David C. Geary; [Неизв.]
Language: eng
Format: epub
Publisher: American Psychological Association

Postnatal Hormones

The relationship between boysʼ postnatal surge in testosterone concentrations and their later behavior and cognition has only been systematically studied during the past decade. This postnatal surge is important for the maturation of boysʼ genitals (Main, Schmidt, & Skakkebæk, 2000), and contributes to the sex difference in sex-typed play behaviors (Lamminmäki et al., 2012), social development (G. M. Alexander, 2014), and perhaps to some of the sex differences in brain and cognition that are covered in Chapters 12 and 13 (Constantinescu, Moore, Johnson, & Hines, 2018).

Independent of prenatal exposure to hormones, boys who have larger postnatal surges in testosterone concentrations engage in more boy-typical play and less girl-typical play than do other boys (Lamminmäki et al., 2012; Pasterski et al., 2015; but see G. M. Alexander & Saenz, 2012). Larger postnatal surges in testosterone concentrations are also associated with delayed babbling in infancy (Quast, Hesse, Hain, Wermke, & Wermke, 2016), smaller vocabularies at 2 years old (Kung, Browne, Constantinescu, Noorderhaven, & Hines, 2016), and relatively poor language development at 4 years old (Schaadt, Hesse, & Friederici, 2015). Moreover, Constantinescu et al. (2018) found that boys with higher postnatal testosterone concentrations are more sensitive to the spatial orientation of objects 5 months later relative to boys with more typical concentrations.

Although it is typically less dramatic than that seen in boys, girls also go through a mini puberty whereby they experience elevated levels of estradiol and progesterone during the first 6 months of life (Winter, Hughes, Reyes, & Faiman, 1976). Girls with higher concentrations of estradiol during mini puberty have more advanced babbling during infancy (Quast et al., 2016; Wermke, Hain, Oehler, Wermke, & Hesse, 2014; Wermke, Quast, & Hesse, 2018) and better language comprehension at 4 years old than do other girls (Schaadt et al., 2015). In contrast, Kung et al. (2016) found that infant girls with higher testosterone concentrations during mini puberty had a smaller vocabulary at 2 years old than did girls with lower early testosterone concentrations. The relationship between early testosterone concentrations and girlsʼ language development is basically the same as that found for boys, although girls of course have lower concentrations on average and still maintain advantages over boys in this area (see Chapter 12, this volume).

In all, these types of studies are intriguing but still in their infancy, so to speak, and we do not fully understand the influences of postnatal hormones on sex differences in childrenʼs behavioral and social development. Nevertheless, the overall findings indicate that the postnatal surge in testosterone and estradiol concentrations are important contributors to many of the sex differences described in this chapter and in later chapters.

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