Role of Genes

• 23 chromosomes carrying genes containing instructions about physical/behavioural characteristics
• One pair are the sex chromosomes - determine the gender of a person
• In a female there's a pair of XX chromosomes, the male pair is XY
• There is usually a direct link between a person's chromosomal sex and their external genitalia
• All embryos start out the same, with external genitalia looking feminine
• At about 3 months, if the embryo will become male, testosterone is produced to cause external male genitalia to develop

Role of Hormones
Development of Genitalia:

• Role of hormones can be studying through the use of intersex children
• In some cases, a genetic male embryo is exposed to too little male hormone and the result is the newborn appears to be externally female
• Conversely, genetic females may be exposed to too much male hormone, resulting in ambiguous genitalia
• Such individuals are usually identified as females at birth and are content
• Research (e.g. Berenbaum and Bailey, 2003) shows that these individuals are often interested in male-type activities

Brain Development:
Sex Differences Explained:

• Male/female brains are different e.g. females seem better at social skills thank boys, but worse at spacial navigation (Hoag, 2008)
• Male brains are exposed prenatally to more testosterone than female brains and this leads to the development of 'masculinised' brain
• If the brain of a genetic female is exposed to too much testosterone, they may masculinise

Animal Studies:

• The effects of testosterone on brain development have been confirmed in animals
• Quadagno et al (1977) found that female monkeys who were deliberately exposed to testosterone during prenatal development were more aggressive