Recent research on gender development is reviewed.
In a recent article, published in the November 2020 issue of Neuroscience and Biobehavioral Reviews, Melissa Hines of the University of Cambridge reviews the latest findings on the development of gender, such as the role of testosterone and socialization and how the two interact (e.g., why girls tend to like the color pink). The present post is a selective summary of this review.
Testosterone and gender development
Let us begin with hormones. Hormones can have a temporary effect on development—an effect that rises and falls depending on the hormone concentration. For instance, estrogen has feminizing effects (e.g., breast development) at puberty.
Hormones can also have organizational influences, causing changes that persist even when the hormone is no longer present.
Testosterone is one hormone with such organizational influences.
Consider the effects of testosterone early in life. The concentration of testosterone is much higher in males than females, particularly from week 8 to week 16 or 24 of pregnancy, and from the first to the third month of infancy.
These are probably the critical periods during which testosterone causes sex-related organizational influences, ultimately reducing female-typical and increasing male-typical behaviors.
Since testosterone influences attributes that show sex differences, it may be helpful to know which behaviors show the largest average sex differences. Those would be gender role behaviors (e.g., preferred toys, sex of playmates), sexual orientation, and gender identity (one’s sense of self as female or male or both). Other characteristics often showing large sex differences include cognitive spatial abilities, empathy, dominance, and physical aggression.
Most of the findings on the effects of testosterone come from animal research or the study of genetic variations in humans. One such genetic variant is congenital adrenal hyperplasia (CAH).
CAH is associated with high levels of testosterone exposure. Compared to unaffected females, females with CAH show more male-typical gender role behaviors and are more likely to be bisexual or homosexual. It has been estimated that about 2 percent ultimately identify as men, which is a much larger percentage than the overall population estimate.
Socialization and gender development
Early testosterone exposure is not the only factor influencing gender behavior. Both self-socialization and external socialization are important too.
External socialization refers to the effects of encouragement of particular kinds of activities by other people (e.g., parents, friends, classmates, teachers).
For example, parents often buy their children toys perceived as gender-appropriate. A recent study of the room contents of 2- to 6-year-old American children found “boys’ rooms contained more play guns, tools, and machines for pretend play; spatial-temporal objects; sports equipment; and vehicles,” while “girls’ rooms contained more dolls, costume jewelry and dress-up clothes, ruffles, and floral furnishings.”
Once they know their sex, children also self-socialize, meaning they imitate the choices of people of their own sex in order to behave in ways expected of them. For instance, they prefer activities and objects favored by those of their sex and show a liking of objects they are told are for their sex (e.g., “dolls are for girls, not boys”).
Interactions of testosterone and socialization: Pink vs. blue
Gender development is also shaped by the interaction between socialization and testosterone. A good illustration concerns color preference (i.e., pink for girls and blue for boys).
Color preference appears to be mostly absent in children younger than 2, even though they seem to show a preference for gender-typical objects (e.g., toys vs. dolls).
The gender difference in color preference seems to emerge between ages 2 and 3. During the next couple of years, this difference becomes larger as children become more deeply aware of themselves as boys or girls, “learning that this will not change over time or if they engage in other-gender activities.”
By adulthood, the pink/blue color preference shows less of a sex difference. Though women, compared to men, still show a marginally greater preference for pink, both male and female adults prefer blue to pink.
This suggests a female preference for pink is not hardwired or sculpted by evolution. So how does this interest for pink develop?
One theory suggests color preference results from the association between colors and emotionally pleasant experiences. And this is partly due to socialization.
Specifically, as Hines notes, “children may learn to like the colors of the toys that are typed for their own sex, pink for girls, and anything but pink for boys, contributing to the stronger preference for pink in girls than in boys.”
In addition, “Girls also may identify strongly with their assigned sex during early childhood, and so may show particularly strong preferences for pink compared to older ages.”
The female preference for pink declines over time as girls have more opportunities to engage with objects not color-coded for their use and as they develop a deeper understanding of their gender.
Concluding thoughts on gender development
Some people believe gender-related behaviors are mainly caused by biological factors (nature), while others believe they are mainly caused by social and environmental factors (nurture).
However, if we were to think of gender-related behaviors in developmental terms, we could see how gender development is affected by numerous influences that interact. An early change in one part of the system, especially during critical periods in development, might significantly reduce or increase the effect of another factor later on.
These changes might concern seemingly trivial differences, like color preference (pink vs. blue), or more significant ones, like empathy, spatial ability, and aggression.