A warning system may err in either way: it may cause us to identify an attacking plane as a seagull, and do nothing, or it may cause us to identify a seagull as an attacking plane, and provoke our inadvertent attack on the enemy. Both possibilities of error can presumably be reduced by spending more money and ingenuity on the system. But, for a given e%- penditure, it is generally true of decision criteria that a tightening of the criteria with respect of one kind of error loosens them with respect to the other.

Thomas C. Schelling, The strategy of conflict, Cambridge, MA, 1980, p. 230