1. A method for responding to a multiple-presence gesture using a touch-sensor, the method comprising: detecting a first presence of an object proximate to the touch-sensor; detecting a second presence of an object proximate to the touch-sensor, the second presence starting after a beginning of the first presence and overlapping in time with, the first presence; and initiating a gesture signal indicating the occurrence of a multiple-presence gesture responsive to each of a set of criteria being met, the set of criteria comprising the second presence starting after a beginning of the second presence and overlapping in time with, the first presence.