Biological Explanations of Gender Development

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Testosterone Production and Brain Development

Testosterone from fetal testes drives male physical and brain development, but structural differences rarely lead to functional differences between sexes.

Biological explanations

Biological explanations examine how chromosomes and hormones influence psychological and behavioural traits.
This includes sex-typical behaviours, such as tendencies associated with masculinity and femininity.

Testosterone

Testosterone is a sex hormone found in higher levels in males.
Testosterone is produced by the fetal testes in males during development.
Testosterone influences the development of male physical characteristics such as genitalia, muscle growth, and secondary sexual traits.

Foetal development

Early in development, all foetuses have similar reproductive structures.
Presence of a Y chromosome activates a gene that triggers the formation of male genitalia.
In the absence of this gene, female genitalia develop, and testosterone production is minimal.

Brain structure

Testosterone affects the developing male brain, leading to structural differences compared with female brains.
However, these structural differences do not necessarily translate to functional differences in behaviour.

Hyde (2005)

A review of meta-analyses conducted by Hyde (2005) found that there was a very small or no difference between the sexes on a majority of measures.
In other words, males and females differ psychologically very little.
Other researchers believe that the combination of sex hormone differences and structural differences result in similar brain function in both sexes.

Genetics

Testosterone production may or may not be what leads to differences in biological sex. There is another explanation.
Laboratory studies conducted on animals shows that differences in sex are not explained by hormonal levels during that early brain development.
It could be that sex differences are directly caused by genes.

Congenital Adrenal Hyperplasia (CAH)

Congenital adrenal hyperplasia (CAH) is a syndrome whereby more testosterone is produced than usual.

CAH

Congenital adrenal hyperplasia (CAH) is a syndrome whereby more testosterone is produced than usual.
It occurs in both genetic males (XY) and females (XX) with different effects:
- If men have CAH, they will have early sexual development but otherwise will not have much of an effect.
- If females have CAH, the increased amounts of testosterone will cause them to become masculinised.

Effects in genetic females

Increased prenatal testosterone in females can influence sex-typical behaviours and physical development.
- Examples include accelerated growth, earlier puberty, and masculinised physical traits (e.g., increased muscle mass, deeper voice).
CAH can cause ambiguous genitalia at birth, irregular menstrual cycle and potential fertility issues later in life.

Effects in genetic males

Males with CAH may experience earlier sexual development and increased growth rate.
- Other physical development is generally typical.

CAH and the brain

By studying individuals with CAH, scientists can better understand how sex hormones influence the brain.
Increased testosterone may affect sex-typical behaviours, such as activity levels or preferences, but effects vary.