Impulsivity and Aggression as Personality Traits in Nonhuman Primates

Abstract

Studies of macaques show that aggressiveness, along with its related cousin impulsivity, is trait-like, showing stable interindividual differences across time and situations. Two variations of aggressive temperament have been described: The first, aggressive temperament or overall aggressiveness, is characterized as competitive, marked by competition and a goal to win. While competitive and aggressive, such individuals seldom engage in violence. In competitive interchanges they often emerge as winners, and are typically high in social dominance. A second type of aggressive temperament leads to impulsive and unrestrained violence. This form of aggression has a strong relationship with impulse-control deficits. Evidence suggests that the two different forms of aggressiveness are mediated by differing systems, with competitive aggression mediated by testosterone. Impulsive aggression is mediated, at least in part by deficits in the serotonin system, with clear genetic and environmental underpinnings. These serotonin-impaired macaques show a variety of antisocial-like personality differences, exhibiting social alienation, sociosexual impairments, as well as impulse-control deficits, violence, and premature death, typically due to violent means. A variety of new molecular genetic studies show that the second form of aggressiveness is modulated, at least in part, by genetic x environmental interactions. (PsycInfo Database Record (c) 2020 APA, all rights reserved)