Simnovic et al. (2013)

Simunovic, D., Mifune, N.(三船恒裕), & Yamagishi, T.(山岸俊男) (2013).
Preemptive strike: An experimental study of fear-based aggression.
Journal of Experimental Social Psychology, 49(6), 1120-1123.
doi: 10.1016/j.jesp.2013.08.003
The mere presence of a potential threat of attack was found to be sufficient to lead significant proportion of participants to engage in preemptive attacks toward potential threats; this response occurred even without an incentive for either party to attack the other. We developed a new experimental game—the preemptive strike game (PSG)—to demonstrate this tendency for defensive aggression. We also found that the rate at which participants attacked an individual representing a potential threat was not influenced by their minimal group membership; participants were no less likely to preemptively attack a member of their own minimal group and no more likely to use aggression against members of another minimal group. These findings indicate a need to further examine the role that fear-based defensive aggression, rather than anger-based spiteful aggression, plays in inter-individual and inter-group conflict.