Berthold demonstrates that animal models when examining the role of testosterone on aggression are not of value. For example, the behaviours of animals and humans are comparable, not identical. This is important because, to measure the effect of testosterone on the roosters, aggressive behaviours were recorded. The aggressive behaviours identified by the roosters include crowing, a behaviour that humans do not exhibit when aggressive. (However, both roosters and humans fight when aggressive.) Therefore, animal models are not of value when examining hormones and behaviour.