The Early Development of Gender Differences (long blog post)

Matthew H. McIntyre and Carolyn Pope Edwards. 2009. “The Early Development of Gender Differences.” Annual Review of Anthropology. Vol. 39, pp. 83-97

The purpose of this review is to summarize the current evidence about the role of biological factors in the development of human gender over a life course.

More specifically this article reviews the role of biological factors in the development of sex differences in human behavior, including biological theories, the developmental course of sex differences, and the interaction of biological and cultural gendering processes at different ages.

The authors use the term gender very broadly, including sex differences and also the cultural and biological processes that shape them.

The article states that current evidence suggests that major biological influences on individuals differences in gender, operate mostly during early development, during and prior to when the individual hits puberty.

Biological Theories About Human Gender

This section focuses on two distinct reproductive strategies called parental investment and mating effort.

Parental Investment
• Include activities that are costly to parents but help contribute to the growth or survival of the offspring (Trivers 1972).
• In almost all mammals, all parental investment is done by females.
• Female psychological adaptations for parental care have been linked to the raise of empathy, and reduced empathy in males, which lowers their thresholds for aggression (baron-Cohen 2002, Campbell 2006).
• Male parental investment has increased during human evolution.

Mating Effort
• Done by mostly males
• Interpersonal dominance striving in men
• The role of the reproductive endocrine system in human sex differences has been assessed using concentrations of sex hormones and can be measured in the blood or saliva.

**How do these evolved processes related to biological gender operate in different cultural and economic conditions?

Evidence From Adult Men and Women

Research shows that the adult sex differences in empathy and dominance striving, can be due to the reproductive endocrine system (example-testosterone).

Hermans et al. (2006) found evidence that an exogenous dose of testosterone reduces empathy . He measured this by unconscious facial mimicry.

It has also been observed, that men’s testosterone levels fall in response to failures in dominance contests of various kinds. Archer (2006) proposed that this response is part of an evolved system, in which men’s willingness to enter dominance contests is determined by their previous record of success.

Studies have identified possible suppressive effects of romantic relationships, marriage, or fatherhood on testosterone levels in men form different societies. Most of these studies have revealed interactions which suggest that social and psychological factors might play small roles in regulating the suppression of testosterone and the mating effort.

Since there are limitations of evidence from adult sex differences, it is more useful to consider the role of biological factors in the earlier development of sex differences in infants and children.

The Developmental Course of Gender

Sex-different patterns of behavior begin to emerge clearly in young children, before puberty and the development of important secondary sex differences.

Edward (1993) noted the below differences between the activities of boys and girls in several human societies.
• From age three, girls spend more time working, whereas boys spend more time in play.
• When playing in groups, children self-segregate by sex, in addition to age.
• Boys begin to spend more time than girls away from home and their mothers.
• Girls engage in more infant contact and care.
• Boys engage in more rough play than girls do.
• Boys engage in more proactive play with weapons and vehicles than girls do.
• Girls engage in more groom than boys do.
Some of these observations are similar to patterns observed in other primates.

I find most of these observations to hold true with our society, but I was surprised that it was the generally the same in other societies.

This pattern of sex segregations plays a major role in the development of adults gender, however the causes of sex segregation remain poorly understood.

Even when adults tried to encourage cross-sex play groups, children would resist and quickly return to same-sex partners when the adult supervision is reduced (Serbin et al. 1977).

Older children use cognitive ideas about gender (cultural norms) during play. Children choose their playmates on the ideas of their categorical understanding of their own gender and the gender of other children (Powlishta et al. 1993), Servin et al. 2001).
Martin & Ruble (2004) say that children as young as fours years old are actively trying to discover stereotypes about men and women by listening to and observing adults. Kids are firstly motivated by knowing that they are girls or boys and that this will not change.

Secondly they are motivated by the desire for in-group dominance.

Some people disagree that cognitive knowledge about gender is necessary. They say that differences among kids in their cognitive understanding of gender are unrelated to the sex of their play partners.

I personally can see how this could be true. I think that the segregation between boys and girls is due to the types of games that are being played opposed to the preferred sex of the play partners.

The Role of Biological Sex Differences

Sex differentiation in mammals is secondly guided mostly by sex hormones produced in the fetal gonads (Hughes 2001).

Since children’s sex segregation in games can be driven by sex differences in play preferences, there is a chance for biological sex differences to influence gender development in small ways.

Girls- show higher fear when confronted with a stimulus, and expressed a shorter threshold of crying, show greater attention to faces by 12 months old

Boys-show a higher motor activity level, show greater attention to mechanical crib mobiles than girls do

Infants who are more reactive to fear develop both greater empathy and social anxiety as toddlers.

Refocusing Biological Studies of Human Gender

The journal suggest that biological studies of gender can be improved by focusing more on infancy and childhood and broader social processes.

Boys with high testosterone are dominant over their peers in adolescence but as they come into contact with other social institutions their lives are more often characterized by delinquency, criminal activities, lack of education, and low social prestige.

Main Points
• For the most part, biological influences on psychological sex differences probably occur early in life.
• Small sex differences in temperament interact with social factors in complex ways that might result in further psychological differentiation but not always in ways that are clearly predicted by existing evolutionary theories.

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