Biological influences on gender

Relationship between sex and gender Biological approach Biological sex produces gendered behaviour. Men = masculine Females = feminine Because of genes and hormones etc.

Deterministic No room for flexibility or choice Programmed by biological factors. The sex of a baby is determined at the moment of conception. An embryo has 23 pairs of chromosomes, each made up of one from the ovum (mother) and one from the sperm (father).

The 23rd pair of chromosomes determines the sex of the embryo. If the embryo inherits an X chromosome from the mother and a Y chromosome from the father, it will develop as a male.

Between 4 and 8 weeks after conception, the gene on the 23rd chromosome instructs the gonads to release hormones. In the male embryo, the testes are instructed to release testosterone which acts on an area of the brain known as the hypothalamus. Without testosterone, the brain would develop in the female form (Green, 1995). In the female embryo, hormone release from the ovaries is very slight.

In the brain

Sexually dimorphic nucleus located in the hypothalamus Clear differences can be seen in the brains of adult men and women, in the function and anatomy of the hypothalamus.

Brain difference 2 Lateralisation in male and female brains. Information passes between hemispheres through the corpus collosum. Research found – when doing a language task, women used both hemispheres Men only used the left.

Analytic thought Logic Language Science and math Holistic thought Intuition Creativity Art and music

Genetic conditions Usual pattern is XY One in 500 men have XXY pattern. Unusually tall, enlarged breasts, likely to be infertile.

Genetic conditions continued XYY male One in a thousand males Taller than average Possibly more aggressive

Genetic conditions continued Inter-sexed babies Characteristics of both sexes E.g. one ovary and one testis. Very rare

Hormonal influences Androgens = male hormones Oestrogens = female hormones Everyone has both Balance is important

Evidence for effect of hormones Young (1966) Doses of male hormones to female rats and female hormones to male rats Resulted in a reversal of mating positions Female rat takes the lordosis position when mating

More evidence Quadangno et al (1977) Female monkeys exposed to testosterone in utero More aggressive than other females

Case study evidence Money and Erhardt (1972) Group of girls exposed to high levels of androgens in utero More tomboyish, higher IQs and ambitious.

Congenital adrenal hyperplasia Exposure to high levels of male hormones in embryo stage. Hines (1994) compared girls and boys with CAH to unaffected boys and girls. Not much difference CAH girls preferred playing with boys

David Reimer Born male Raised female after his penis was accidentally burnt off during circumcision Did not successfully identify as female

Correlational studies Deady et al. (2006) Negative correlation between levels of testosterone in women and scores on BSRI for maternal drive.

2D:4DR Mixed findings on finger ratio (2D:4DR) Significant findings in males – more feminine sex role on BSRI had a finger pattern which showed lower exposure to androgens and higher to oestrogens in utero.

To evaluate Consider the nature/nurture debate How strong is the evidence that biology has an effect on gender? Consider the studies you have looked at in terms of the reliability of the findings and the methodology used.