Zhen Li¹ (), Ning Tang¹, Siyi Gong², Jifan Zhou¹, Mowei Shen¹, Tao Gao²; ¹Zhejiang University, ²UCLA

The tragedy of human warfare is that settlements are difficult to reach even when both sides are suffering. Economic theory has posited that mutually salient rallying points, even when completely irrelevant to human conflicts, can facilitate peace settlement - a speculation that has never been examined with experiments. Here we investigate whether perceptual gestalts, a universal perceptual phenomenon, can function as rallying points influencing war strategies. We devised a 2D multiplayer strategic war game, where participants could freely deploy their troops. Unlike most zero-summed war games, players’ task was not annihilating the opponent but accumulating maximum wealth. Just like the real world, while expansion could bring wealth, a war of attrition could be mutually destructive as 1) troop logistics increased with the extension of supply lines, and 2) casualties could be high even for the winner. To examine the role of perceptual gestalt at war, for one group of participants (‘Grouping condition’) the battlefield grids were perceptually organized into different groups based on war-irrelevant color. Compared to the ‘Non-Grouping’ condition where all grids shared the same color, task-irrelevant perceptual grouping influenced war strategies in several ways: Firstly, it reduced the number and intensity of wars. Secondly, it constrained strategic decisions: Despite having freedom to develop troops in any direction, participants nevertheless overwhelmingly fought along the direction of perceptual grouping. Thirdly, it altered the dynamics of war: While wars resembled ‘blitz’ in the ‘Non-grouping’ condition, with fast troop movements causing high annihilation rate (42%), perceptual grouping led to ‘trench warfare’ with lower annihilation rate (20%). Moreover, the hierarchical structure of perceptual grouping biased how three players formed alliances, with powers residing in color groups closer in the perceptual hierarchy more frequently allying. Collectively, these findings suggest perceptual gestalt can serve as a mutually acknowledged rallying point constraining human warfare decisions.