Take, for instance, the cooperation of 'live and let live' which flourished between enemy soldiers in the First World War (Axelrod 1984). This might be accounted for in various ways. It may have arisen as the result of a soldier shooting — out of distraction, boredom, or nervousness -— at some clearly non-human target in the opposite trench. Or it may be that soldiers on both sides stopped shooting at regular intervals because they happened to have their meals at the same hours of the day. Such random signals may eventually have been 'interpreted' by one side as an inclination on the other towards an implicit truce, and they may have responded with other signals; first just to test for possible misunderstandings, then with increasing conviction, until the exchange slowly assumed the features of a stable cooperative abstention from mutual injury.

Diego Gambetta, Trust - Making and Breaking…, loc. 2789