Todd K. Shackelford

“With deep theoretical roots (e.g., Bandura 1973; Dollard et al. 1939), there are at least two functions of aggression: aggression that
serves to attain some goal of the perpetrator (i.e., instrumental aggression, which can be considered planful and cool-headed) and aggression that is impulsively enacted in response to some provocation, real or imagined (i.e., reactive aggression, which can be considered unplanned and hot-headed). A simple example of instrumental aggression is an attack on the victim for some material reward, such as money or an iPhone. Reactive aggression is exemplified by an outburst to a perceived or actual slight. For child developmentalists, the distinction is important because each is associated with a unique developmental trajectory and consequent socioemotional outcomes. For example, reactively aggressive children are more apt to display poor psychological adjustment because their dysregulation leads to related
social difficulties such as peer rejection (Coie and Koeppl 1990). By contrast, instrumentally aggressive children are not necessarily dysregulated. Moreover, their
success at goal attainment may even lead to positive peer regard.”
― Todd K. Shackelford, The Evolution of Violence