Aggression - Hormonal Mechanisms

Aggression - Hormonal Mechanisms

1. Testosterone is a male hormone, females have very low levels and it can be associated with agg. When T levels peak around the start of puberty, there is a corresponding peak in agg levels among boys. But men with more T do not necessarily become more agg.

2. The effects of T are shown by: Dabbs et al 1987: Measures salivary T in violent & non violent criminals. Highest levels of T found in those of violent crime. Lowest levels of T in those who committed non violent crime. Lindman et al 1987: Similar test on non prison population, found that young M who beh agg when drunk had higher levels of T than those who did not act agg.

3. It is influential during two life periods: A few days after birth during which sensitisation of neural circuits occurs. Adulthood when T modulates NT pathways.

4. Human & non-human animal aggression Much research has been carried out using NHA. Classic method: Castrating a M animal to dec agg & when T is replaced through hormone therapy, agg is restored to previous levels. Timing of castration has an effect: At birth they have lower level of agg even if given huge doses of T as adults.

5. Other causes of low T include: As a man ages, the amount of T in his body gradually declines. This starts after age 30 and continues throughout life. Other causes of low T levels include:

   • Hemochromatosis (too much iron in the body) - this causes a dec in T & agg. Opposing this, not much iron in the body could inc T & inc agg. A Dysfunction of the pituitary gland - Over functioning of PG could lead to an inc in T & agg.

6. IDA

   • Real World Application: If we know about the link we can help to treat their beh. There would be ethical issues associated with giving people drugs simply to alleviate agg, or male castration, even if it may be in the interests of multiple parties.
   • Reductionalist: Bio links are well established in NHA but humans are far more complex. We cant reduce complex human beh to one explanation. Also need to consider genetic factors, brain structure & enviro factors.
   • Gender Bias: Most R into T is done on males.
     • Baucom 1985: found that women with inc T levels had inc occupational status. Findings indicate women may also respond to challenging situations with inc T. May also display dominance & agg. Saying that W are the same as M. W naturally display the characteristics of agg beh & so, do well in business

7. Research

   • Higley et al 1996: Reported that individuals with raised levels of T exhibit signs of agg, but rarely commit agg acts, suggesting that social and cog factors play a mediating a role. Suggesting other factors play a part, not just T levels - Link to reductionis
   • Wingfield 1990: Suggested that in monogamous species, T levels should only rise above the baseline breeding level in response to social challenges such as male-male agg or threats to status.
     • We would expect a similar effect in humans as they are considered monogamous. So we might expect M to be more agg than F as they are challenging reproductive competition.
   • Delville et al 1997: Found that drugs that inc S production lead to reduced levels of agg.
     • Linnoila & Virkunen 1992: Found a relationship between low levels of S and highly explosive violent beh.
       • Suggest that a lack of S is linked to agg, but agg beh could be due to other factors such as S.
   • Connor & Levine 1969: Found that rats castrated after birth had reduced agg when tested as adults, suggesting a link between agg & T. However, rats castrated after puberty could be made agg with injections of T, while the early castrated rats could not, suggesting a developmental factor.
     • Supports theory of T causing agg beh. Ethical issues = not valid = not applied to humans.
   • Brook et al 2001: > MA of 45 studies & found a + correlation between T & agg. This is low, it could be that inc agg causes inc T , as opposed to inc T causing inc agg. We dont know cause & effect.
   • Albert 1993: Claims that despite the studies showing a + correlation between T & agg, other studies find no relationship. He points out that many studies use samples of men within prisons & use self report measures (social desirability). Self reports = social desirability = invalid if they lied.

8. Testosterone's link to serotonin Low levels of S = associated with agg. Suggesting that T might not be the only cause of agg & not having a direct link.