Symmetry breaking of escaping ants
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Symmetry breaking of escaping ants is a herd behavior phenomenon observed when ants are constrained to a cell with two equidistant exits and then sprayed with an insect repellent. The ants tend to crowd one door more while trying to escape (i.e., there is a symmetry breaking in their escape behavior), thereby decreasing evacuation efficiency.
This phenomenon arises in experiments where worker ants are enclosed in circular cells with a glass cover in such a way that they can only move in two dimensions (i.e., ants cannot pass over one other). The cell has two exits located symmetrically relative to its center. The experiments consisted of two different sets of trials. In the first set of trials, both exits were opened at the same time, letting the ants escape. After 30 repetitions, one door was used 13.666% more than the other. In the second set of trials, the configuration was identical, but a few seconds before opening the doors, a dose of 50 μL of insect repellent was injected into the cell at its center through a small hole in the glass cover. After 30 repetitions, one door was used 38.3% more than the other.
