BIOLOGICAL INFLUENCES ON GENDER
To read up on biological influences on gender, refer to pages 244–253 of Eysenck’s A2
Level Psychology.
Ask yourself
 Is biology destiny when it comes to gender development?
 How does Money’s research support the role of biological factors even
though initially he claimed the study supported the role of nurture?
 Do evolutionary roles of “man as hunter” and woman as “child bearer”
explain gender differences today?
 How does the biosocial approach combine the influences of nature and
nurture?
What you need to know
THE ROLE OF HORMONES THE BIOSOCIAL
AND GENES IN GENDER
APPROACH TO GENDER
DEVELOPMENT
DEVELOPMENT



Prenatal sexual
development
The influence of sex
chromosomes
The role of
hormones


Research evidence
Evaluation
EVOLUTIONARY
EXPLANATIONS OF
GENDER DEVELOPMENT:
SOCIOBIOLOGY


Research evidence
Evaluation
The Role of Hormones and Genes in Gender Development
Prenatal Sexual Development
When the ovum (egg) combines with a sperm, the zygote that is formed will either
have XX chromosomes, and be a girl, or XY chromosomes, and be a boy. The
sequence of sex development is as follows:
 For 7 weeks development is virtually identical for girls and boys.
 The Y chromosome then induces the release of testosterone, which
stimulates the growth of male sex organs. If no testosterone is released, the
foetus develops female reproductive organs.
 In a rare condition, known as complete androgen insensitivity syndrome,
genetic males (i.e. those with XY chromosomes) are insensitive to the male
hormones and do not develop male genitalia. They are born looking like girls
and are often brought up as girls because the condition is not usually
detected until puberty.
The Influence of the Sex Chromosomes
We have discussed one influence of the Y chromosome: to induce the release of
testosterone in the developing foetus.
The Y chromosome is one fifth of its size, hence boys carry less genetic material than
girls, and this may be one reason why males are more vulnerable than females
throughout their lives. Montagu (1968, see A2 Level Psychology page 245) listed 62
specific disorders that are largely or wholly due to sex-linked genes and found
mostly in males, including some very serious ones, such as haemophilia, as well as
less important ones such as red/green colour-blindness.
The Role of Hormones
The role of hormones in sexual development is of enormous importance.
Each sex has identical sex hormones; the difference between them is the amount
they produce. Within normal biological development, females produce a
preponderance of female sex hormones (oestrogen and progesterone), whilst males
produce a preponderance of androgens (a collection of male hormones) of which
one of the most important is testosterone.
Up to about the age of 8–10, negligible amounts of sex hormones are produced by
either sex but after that both sexes produce more male and female hormones. From
around 11 years of age, both girls and boys increase their production of female
hormones but females produce far more than boys. Conversely, once children reach
puberty both sexes increases their production of male sex hormones rapidly but
boys more so than girls.
RESEARCH EVIDENCE
 Young, Goy, and Phoenix (1964, see A2 Level Psychology page 246)
demonstrated that pregnant monkeys injected with androgens have given
birth to females with masculinised genitalia and who act in masculine ways,
such as being threatening and aggressive, engaging in rough-and-tumble
play, and mounting females.
 Knickmeyer et al. (2005, see A2 Level Psychology page 246) studied the fT
levels of in the amniotic fluid (the fluid around the baby in the uterus) of 35
male and 23 female babies. In animals, foetal testosterone (fT) plays a central
role in organising the brain and in later social behaviour. In humans it has
been linked negatively with language development and eye-contact, and
positively with spatial ability. Based on their mothers’ assessment of their
language skills, quality of social relationships, and restricted interests at aged
4, the researchers found a negative correlation between fT and the quality of
social relationships and a positive correlation between fT and restricted
interests in the boys. This indicates that testosterone may negatively affect
social relationships.
 Dalton (1969, see A2 Level Psychology page 246) summarised research on the
effect of sex hormones on the menstrual cycle. Sex hormones have been
linked to pre-menstrual syndrome, which occurs when progesterone levels
are low. Pre-menstrual syndrome/tension tends to be a catchall phrase for a
variety of symptoms, including depression and irritability. Dalton reported
that many studies showed behaviour change that could be attributed to the
menstrual cycle. 63% to 84% of crimes committed by women occur in the
pre-menstrual period. Accident and suicide rates increase, while there is a
decline in the standard of schoolwork, in scores on intelligence tests, and in
speed of response.
 Mcfarlane, Martin, and Williams (1988, see A2 Level Psychology page 247)
report different findings. They, and others, maintain that although a small
percentage of women do suffer relatively intense periodic mood swings
related to their menstrual cycle, in most women there is little relationship
between the menstrual cycle and mood. They point out that there may be a
self-fulfilling prophecy operating—women expecting to feel moody and
depressed at this time of the month may make this more likely, and may
make them more aware of clumsiness, etc. than at other times of their
menstrual cycle.
 Collaer and Hines (1995, see A2 Level Psychology page 247) reviewed the
somewhat inconsistent findings from numerous studies of the effect of sex
hormones on behaviour. They argued that there is good evidence for at least
three effects.
o First, male sex hormones increase the likelihood that the child will
enjoy rough-and-tumble play and physical activity generally.
o Second, exposure to high levels of male sex hormones at an early age
affects sexual orientation in adolescence.
o Third, male sex hormones lead to an increase in aggressive behaviour.
The Biosocial Approach to Gender Development
The biosocial approach to gender development emphasises that it is the interaction
of both nature and nurture that is important rather than one or the other. The
theory fully acknowledges the importance of biology so it would involve all the
biological research just covered, but it also acknowledges that social factors may
interact with these to influence gender identity.
Biosocial theory was first advanced by Money and Ehrhardt (1972, see A2 Level
Psychology page 247) who start by proposing that there are a number of critical
events that affect the early development of the child. These events begin before
birth with the biological influences covered in the previous section. These biological
factors obviously have a large influence on the child. However, from birth onwards,
social factors also begin to play an important part. As we have already seen, once a
child is labelled as a boy or girl they are treated very differently, and these social
factors interact with the biological ones to determine the child’s gender identity.
In the majority of cases, the child’s biological sex matches the gender of upbringing
and there are no problems. However, some individuals, known as intersex children,
are born with ambiguous genitals and are not obviously one sex or the other. Money
believes that provided a child’s sex of rearing is decided before their third birthday,
then social factors are so strongly influential that such children will accept their
assigned gender identity. The third year is another critical period and since a child’s
gender identity is established by that age, then, according to Money, it cannot
thereafter be changed without causing the child serious psychological problems.
Research evidence
 Goldwyn (1979, see A2 Level Psychology page 248) cites the case of Mrs DW
who had androgen insensitivity syndrome and was brought up as a woman.
Although informed in her teens, at no time did she ever feel masculine and
was completely happy with her eventual role as wife and adoptive mother.
This, of course, is a case study of one, which makes it hard to draw firm
conclusions. It also isn’t entirely clear whether we can say that Mrs DW was
influenced by social factors (reared as a girl) or biological ones (exposure to
male hormones).
 Imperato-McGinley et al. (1974, see A2 Level Psychology page 249) described
a family in the Dominican Republic, a case that contradicts the theory. Four of
the sons appeared biologically to be female when they were born and they
were reared as girls. However, at the age of about 12, they developed male
genitals and started to look like ordinary adolescent males. In spite of the fact
that all four of them had been reared as girls, and had thought of themselves
as females, they seemed to adjust well to the male role. Nevertheless, it is still
difficult to draw firm conclusions as the male role is more respected in this
community than is the female one, so their acceptance of a changed gender
identity could have been influenced by social factors as well as biological
ones.
 Colapinto (2000, see A2 Level Psychology page 248) reports the case of David
Reimer, which does not support the biosocial approach. Reimer was raised as
a girl after his penis was accidentally burnt off during a botched operation at
8 months. According to Money (1975), this was a success but the “girl” was
never happy as a girl and once the truth was revealed to her, she reverted to
being a male.
EVALUATION
 Support from research evidence. There is a considerable body of evidence
to indicate that biosocial theory, with its emphasis on the interaction of
biological and social factors, has a lot to recommend it. Several case studies,
such as that of Mrs DW, demonstrate that it is quite possible to be content
with the gender identity of upbringing even when it clashes with that of the
chromosomal sex.
 Lack of support in specific aspects of the theory. The more specific
assertion of Money and Ehrhardt (1972) that in the first two-and-a-half to
three years a child’s sense of itself is flexible enough to allow its sexual label
to be changed without undue disturbance is now somewhat discredited,
especially in light of the Reimer case.
 Contradictory evidence from research. Findings from other studies are in
fairly direct conflict between biological and social factors. For example, the
case of the four children in the family from the Dominican Republic seems to
show that biological factors cannot always be outweighed by social factors.
Evolutionary Explanations of Gender Roles: Sociobiology
Sociobiology applies the principles of evolution to the understanding of social
behaviour. The theory argues that the behaviour of all animals has evolved so that it
maximises the likelihood that individuals will pass on their genes to future
generations. In human terms, this means that both women and men unconsciously
behave in ways that promote conception, birth, and survival of their offspring. In
pursuit of this end, the optimal mating behaviour differs dramatically between men
and women (Trivers, 1972, see A2 Level Psychology page 249). Since a man can, in
theory, impregnate many women within a short time and will only waste some
easily replaceable sperm if sexual intercourse does not result in pregnancy, it is in
his interest to be promiscuous and seek out good child-bearers. A woman, who has to
invest a great deal more in bearing each child than does a man, is likely to be far
more choosy when selecting a mate. She will be coy, take her time, and choose a man
who can provide for her and her infant, perhaps an older man who is established in
his career.
RESEARCH EVIDENCE
 Buss (1989, see A2 Level Psychology page 250), in an extensive study of 37
cultures (in 33 countries), analysed the results of more than 10,000
questionnaires asking respondents to rate a number of factors such as age,
intelligence, and sociability for their importance in a sexual partner.
Consistent with sociobiological theory, men valued physical attractiveness
more than did women, while women were more likely than men to value
good earning potential and high occupational status. In all the cultures both
women and men preferred the man to be the older of the pair. It is worth
noting however that gender differences in the importance of physical
attraction are stronger when people estimate its importance (as in
questionnaires) than when they actually interact with someone.
 Williams and Best (1982, see A2 Level Psychology page 250) explored gender
stereotypes in 30 different national cultures. They found that there were
many similarities across the various cultures. Men were seen as more
dominant, aggressive, and autonomous, in a more instrumental role. Whereas
women were more nurturant, deferent, and interested in affiliation, being
encouraged to develop an expressive role. This finding was also supported by
Barry, Bacon, and Child (1957).
 Mead (1935, see A2 Level Psychology page 250) generally hypothesised that
gender differences are cultural. Nevertheless, within each cultural group
studied by Mead the males were generally more aggressive than the women.
Even in the Tchambuli, in which gender roles showed some reversal from the
usual patterns, it was the men not the women who did most of the fighting in
times of war. This supports the idea of inherited gender-role behaviours.
 Davis (1990, see A2 Level Psychology page 250) conducted research on
“personal” advertisements. This indicated that there are consistent
differences in what men and women desire in a sexual partner. Consistent
with sociobiological theory, this analysis found that men tended to

emphasise their wealth or other resources while looking for women younger
than themselves. In contrast, women indicated that they were looking for a
high-status, wealthy man, and mentioned their own physical attractiveness.
Nevertheless, physical characteristics were the most desired attributes for
both men and women.
Singh (1993) found that men are attracted to women with a low waist-to-hip
ratio (with the waist smaller than the hip!) and this is related to childbearing
potential.
EVALUATION
 Support from cross-cultural studies. Most cross-cultural studies have
indicated that the cultural expectations and stereotypes for boys and girls are
surprisingly similar in otherwise very different cultures.
 Contradictions from cross-cultural studies. However, it is important to
look in more detail at some of the findings. In the study by Buss (1989) there
were some significant findings that have received far less attention. Both
men and women placed exactly the same four attributes highest on their
preference list—mutual attraction, dependable character, emotional stability
and maturity, and pleasing disposition. Their rankings of qualities also placed
the same four items on top—kind and understanding, intelligent, exciting,
and healthy (Smith & Bond, 1993, see A2 Level Psychology page 251). So the
support for the sociobiological view that there are large and significant
differences in the attributes universally sought by males and females is not
entirely convincing.
 Studies do not offer complete support. Williams and Best (1982) also do
not offer unequivocal support. They found that the consensus of what women
and men find desirable was true in collectivistic societies but weaker in
individualistic societies where gender equality is more influential. This
suggests that socialisation practices as well as biology can influence the
characteristics men and women find desirable.
 Problems with the actual theory. The major limitation of sociobiological
explanations in general is that they use hindsight to explain almost any
behaviour in terms of why it has evolved. The reasoning is post hoc (after the
event) and it is possible to argue that almost any observed gender
differences are due to evolution.
 Lack of empirical evidence. The hypotheses suggested by the
sociobiologists often have no empirical evidence to support them, they are
merely conjecture (sometimes referred to as stories).
 No predictive power, so not a scientific theory. One important
characteristic of a good theory is that it can be used to make predictions
about the future. However, sociobiology has little predictive value. There are
so many possibilities with regard to how behaviour may evolve that
prediction becomes impossible.
 Difficult to untangle the effects of culture from those of evolution.
Despite Buss’ work, there are significant historical and cultural differences in

heterosexual mate selection. For example, men’s preference for younger
women was considerably greater in the past than it is now and is greater in
traditional than in modern societies (Glenn, 1989, see A2 Level Psychology
page 252). The difficulty of separating culture from evolution will always
mean that sociobiology is likely to remain controversial.
Problem with the argument that certain patterns of behaviour are
“hard wired” by evolution and cannot easily be influenced by other
factors. When we look more closely at both human and non-human animal
behaviour concerning sex and infant care, we find a huge variety of
behaviours within a single species, and changes in environment can have a
profound effect on this behaviour. Even species of birds change their mating
behaviour quite drastically according to the availability of good nesting sites
and food sources, so it would be very surprising if humans were less
adaptable. Having plasticity of behaviour rather than rigidly determined
invariant patterns can have a great survival value (Fausto-Sterling, 2000, see
A2 Level Psychology page 252).
So What Does This Mean?
So is biology destiny? There is no doubt that there are important biological
influences on our behaviour, as illustrated so poignantly by the case of David
Reimer. In addition, evolution is certain to have shaped some of our behaviour, just
as surely as it has shaped our bodies. Nevertheless, it would seem fair to say that
however important biological factors are, they can only provide a partial
explanation for the development of gender roles. We have already seen how
important social and cognitive factors, including the self-fulfilling prophecy, are in
shaping behaviour. In the next section we will look at other influences before we try
to draw tentative conclusions about the extent to which biology is destiny.
Over To You
1(a). Outline the role of hormones and genes in gender development. (10 marks)
1(b). Evaluate the evolutionary explanation of gender roles. (15 marks)