Transcript Biological influences on gender

Biological influences on
gender
Relationship between sex and gender
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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
Holistic
thought
Logic
Intuition
Language
Creativity
Science
and math
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
Female rat takes the
lordosis position
when mating
• Young (1966)
• Doses of male
hormones to female
rats and female
hormones to male
rats
• Resulted in a reversal
of mating positions
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.