The role of chromosomes and hormones

• Chromosomes


  found in the nucleus of living cells and carrying information in the form of genes. The 23rd pair of chromosomes determine biological sex. All normal egg cells have an X chromosome so the sex is determined by the sperm and if it carries a 'sex-determining region Y' (SRY) that produces androgens (male sex hormones).
• Hormone


  a biochemical substance that circulates in the blood but only affects target organs. They are produced in larger quantities but disappear quickly. Their effects are very powerful. In the womb, hormones act upon brain development and cause the production of reproductive organs. At puberty, a burst of hormonal activity triggers the development of secondary sexual characteristics such as pubic hair. Males and females produce much of the same hormones, in different concentrations.
• Testosterone in foetal development


  a hormone from the androgen group that is produced mainly in the male testes (smaller amounts in the female ovaries). Associated with aggressiveness. It controls the development of male sex organs during foetal development. If a genetic female produces high levels of testosterone during foetal development, male sex organs may appear.
• Testosterone and aggression


  High levels of testosterone are associated with high levels of aggression due to adaptation. Aggression towards rivals allows males to compete for the opportunity to mate with a fertile female. In addition, the fact that women tend to children means that men are more likely to take the hunter role and success would be enhanced by aggressiveness.
• Oestrogen


  The primary female hormone plays an important role in the menstrual cycle and reproductive system. Oestrogen determines female sexual characteristics and menstruation. It also may cause heightened emotionality and irritability during their menstrual cycle (post-menstrual syndrome (PMS)). In extreme cases, PMS has been used as a defence in cases of shoplifting and even murder. However, some researchers dispute the existence of PMS as a viable mental category.
• Oxytocin


  a hormone which causes contraction of the uterus during labour and stimulates lactation. Women typically produce much larger amounts of oxytocin than men, particularly as a result of giving birth. It reduces the stress hormone cortisol and facilitates bonding. It has been referred to as the 'love hormone'. It is released in massive quantities during labour and after childbirth, making new mothers feel 'in love' with their babies.
• Oxytocin in men


  The fact that men produce less of this hormone has fuelled the stereotype men are less interested in intimacy and closeness in a relationship. However, evidence suggests both sexes produce oxytocin in roughly equal amounts in events such as kissing or sex.
• Evidence for Testosterone


  There is evidence that supports the role of sex hormones in gender development even in mature males. Male hypogonadism is when male testes fail to produce enough testosterone, Wang et al (2000) gave 227 men with this disorder testosterone therapy for 180 days. Testosterone replacement improved sexual function, libido and mood, and significantly increased muscle strength. This shows testosterone exerts a powerful influence on male sexual arousal, as well as physical development in adulthood.
• A counterpoint to testosterone studies

  A study by O'Conner et al 2004 increased testosterone in healthy young men. There was no significant increase in sexual activity or desire in participants. Notable the men experienced no change in aggression either. This suggests in 'normal' adults, additional testosterone doesn't have an effect on sexual or aggressive behaviour, this however doesn't challenge the role of testosterone in early development.
• Limitation of Testosterone explanation

  Biological accounts ignore the role of social factors in gender-related behaviour. Hofstede et al (2010) claimed that gender norms are more a consequence of social norms rather than biology. Countries that emphasise individualistic culture tend to be more masculine in their outlook, including advanced capitalist societies such as the UK and the US. Traditional masculine traits are more highly valued within these societies. Challenging bio explanations, suggesting social factors may be more important in shaping gender behaviour and attitudes.
• Reductionism of biological explanations of gender


  Another limitation of the bio explanation is that it is reductionist. Reducing gender to the level of chromosomes and hormones and accused of ignoring other explanations. The cognitive approach suggests the impact of schema. Even though changes may happen due to brain maturation they are not adequately explained by the bio model. The psychodynamic approach acknowledges maturation but also the influence of factors like family. This suggests gender is more complex than its biological influences alone.