Based on the premise that chemicals such as hormones or pharmaceutical agents affect neuronal responses such as mood and behavior, it tries to explain how the body’s internal chemical reactions have overt effects on how humans react to the environment. In the study done by Drs. Kruk, Hala´sz, Meelis and Haller on the “Fast Positive Feedback Between the Adrenocortical Stress Response and a Brain Mechanism Involved in Aggressive Behavior,” the relationship between the body’s stress response and aggressive behavior is looked at. It was the aim of their experiment to test whether there was a “mutual stimulatory interaction between brain mechanisms controlling aggressive behavior and the stress response” (Kruk, Meelis, Halász and Haller 2003). The investigations cross traditionally disparate domains of psychology as it takes an in-depth look at the connection between Behavioral, Social and Clinical Psychology – the link between integrative physiological investigation (e.g., in the role of specific neural structures, such as the hippocampus, in eliciting the stress response), frustration and aggression, and even psychopharmacology. Theoretically, it tried to prove that aggression is more of a biological response, and as such could be controlled, or even induced, by pharmacological means.
The Experiment and the Results
In the experiment, 53 rats were used as the main participants for five different experiments aimed to study whether stimulating the brain's aggression mechanism raised blood levels of a stress hormone and whether higher levels of the same hormone led to the kind of aggression elicited by that mechanism (Willenz 2004). Rats, whose neurophysiology is similar to ours were prepared by means of surgically implanting electrodes designed to stimulate the aggression-related part of the rat, his hypothalamus, a mid-brain area associated with emotion. Opponent rats were given an intraperitoneal injection of morphine before encounters with their electrode - implanted counterparts in order to produce profound sedation and analgesia during attacks (Kruk, Meelis, Halsz and Haller 2003). A series of five different experiments whereby the hypothalamus was electronically stimulated and measurements on the level of corticosterone (a substance akin to cortisol which humans produce under stress) present and the concomitant increase or absence of aggressive response in the rats in the presence or absence of an enemy or another attacker was undertaken. In the first two experiments, the rats' hypothalamuses were stimulated and their response to the absence and presence of an aggressive and non-aggressive opponent were measured. The results showed that "that activating the hypothalamic aggressive area is in itself a sufficient condition to obtain a considerable adrenocortical response. The confrontation with an opponent apparently is not required. The small increase observed in the absence of stimulation and opponent is probably due to an anticipatory stress response to the introduction into the test cage, a setting where these rats had fought before" (Kruk, Meelis, Halsz and Haller 2003). In the next two experiments, they determined the effects of a surge in plasma corticosterone and assessed the duration of their effects on attack thresholds. It was found that the levels of plasma corticosterone induced attack behavior in the rats. The last experiment tried to determine what would happen if the rats underwent an adrenalectomy and the stress response was chemically induced