Hormones in Context:
Collins Dictionary(1) gives the psychological definition of aggression as "a hostile or destructive mental attitude or behaviour" and of 'aggressive', "quarrelsome or belligerent, assertive, vigorous (an aggressive businessman)"
The Reader's Digest Dictionary(2) definition of aggression is, similarly, "Hostile action or behaviour" and of 'aggressive', "inclined to provoke an argument or hostility; belligerent, assertive, bold, forceful (an aggressive salesman), which implies threat or intimidation.
Even here there are shades of meaning where the former implies violence and a deliberate attempt to inflict damage, while the latter does not necessarily do so. However in biological studies the word refers to precisely defined behaviour individual to that study, usually as a component of direct competition.
It is observed by particular behaviours performed in particular circumstances. Often the behaviours are stereotyped. These might involve biting, goring, butting, hitting, play fighting or rough and tumble play. Alternatively submissive behaviours may be recorded.
Often it is defined by the outcome in terms of obtaining a resource at the expense of another. By this definition, bird song as a means of protecting a territory or attracting a mate could be regarded as aggressive behaviour. For that matter, the definition would include any actions by females that improve the quality of a potential mate. Females are, generally speaking, in a seller's market, but in most communal species, there is a hierarchy of females, just as there is of males.
It is a general, but not universal, rule that males secrete more testosterone than females and it is a major influence on male sexual development. While males appear to engage in more frequent and conspicuous fighting, studies of females is complicated by variations of their hormones. Or to put it another way, it is not so easy to label female behaviours in terms of hormones.
Hormones, testosterone in particular are said to 'organise' a behaviour during development or 'activate' the behaviour under certain conditions. This tends to lead to unwarranted assumptions. A simple hormone cannot, by itself, organise a complex behaviour. It can only encourage or inhibit the development of structures that are already present, by perhaps sensitising receptors preferentially for a potential later behaviour
Likewise, the idea that testosterone 'activates' a behaviour leads to the assumption that it causes it, when it may simply facilitate the occurrence of the behaviour.
Among humans, male aggression is seen as more of a problem than female aggression and, if it is assumed that females do not fight, then they are less likely to be studied. Studies of male fighting have focused on demonstrating the hormonal link. If there is no clear link for females, there are not likely to be any published.
Bland, J.,(2004) About Gender: Testosterone and Aggression.
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Web page copyright Derby TV/TS Group. Text copyright Jed Bland.
06.05.98 Last amended 12.03.02, 07.03.04