Modification of experimentally induced aggression by temperament dimensions

The present paper investigates the question of how experimentally induced aggression can be modified by different temperament dimensions, and if subjects scoring high on different aspects of temperament differ with respect to responses to a serotonergic drug, since serotonin responses have been shown to be related to impulsivity and aggression. In a sample of 40 healthy males divided either according to the temperament dimension of Tempo or Lack of Impulse Control as measured by the EASI Temperament Inventory were randomly assigned to four groups of a 2×2 design comprising the factors of ipsapirone placebo and experimental induction of aggression by a modified Master Mind game and a control condition. Emotional, behavioral, and hormone responses were recorded. The major findings were that induction of aggression increased emotional aggression in high Tempo scorers (high T) and behavioral aggression (punishing a putative coplayer by noise) in high scorers on Lack of Impulse Control (high LIC). The serotonergic drug induced anger in high T under control conditions but reduced it upon experimental induction of aggression, whereas the opposite held true in high LIC. The hormone responses (cortisol and prolactin) to the drug under control and aggression induction conditions were also different for high T and high LIC. Results were interpreted in terms of different receptor sensitivities of the serotonergic and the dopaminergic system in the two temperament groups.