A hormone is a biochemical produced by the glands of the endocrine system which is transported by the bloodstream to specific cells and organs around the body in order to initiate specific biological responses. The human body can produce a large number of hormones, many of which have a large influence on our emotions and behavior. Common examples are adrenaline, oxytocin, oestrogen, and testosterone, which I will be using to demonstrate the vast influence which hormones have over our everyday lives.
Testosterone is the hormone responsible for the development of secondary sexual characteristics in males (development of facial hair, deepening of voice, increased muscle mass, etc.) and is secreted from the testes and ovaries, although only in small amounts by the latter. It is essential for reproduction in males and has been strongly linked to aggressive behaviors.
One study which adequately demonstrates this link is Berthold’s 1840’s study on the effects of testosterone on animal behavior. In this quasi-experiment six roosters were castrated. One group was left without testicles, one had them surgically reattached, and one had another rooster’s transplanted. Both of the groups which had been given testicle transplants behaved normally (fighting, crowing, strong sex drive) despite the fact that the testicles did not re-establish the connections they had originally had, while the control group showed decreased levels of aggression and lack of desire to mate. Berthold concluded that the testes must be responsible for secreted some chemical which is linked to these behaviors.
Because this study used roosters we can argue that the results should not be generalized to fit humans, however, more recent research has reinforced this link and I chose this study because it was one of the earliest and sparked further enquiry into the area. This study demonstrated a clear cause-and-effect link between the testes and traditional male behaviors because removal the testicles directly lead to less dominant behaviors in the control group.
