Displacement activities occur when an animal experiences high motivation for two or more conflicting behaviours: the resulting displacement activity is usually unrelated to the competing motivations. Birds, for example, may peck at grass when uncertain whether to attack or flee from an opponent; similarly, a human may scratch their head when they do not know which of two options to choose. Displacement activities may also occur when animals are prevented from performing a single behaviour for which they are highly motivated. Displacement activities often involve actions which bring comfort to the animal such as scratching, preening, drinking or feeding.