Displacement activities occur when an animal experiences high motivation for two or more conflicting behaviours: the resulting displacement activity is usually unrelated to the competingmotivations. 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 bringcomfort to the animal such as scratching, preening, drinking or feeding. In the assessment of animal welfare, displacement activities are sometimes used as evidence that an animal is highly motivated to perform a behaviour that the environment prevents. One example is that when hungry hens are trained to eat from a particular food dispenser and then find the dispenser blocked, they often begin to pace and preen themselves vigorously. These actions have been interpreted as displacement activities, and similar pacing and preening can be used as evidence of frustration in other situations. Psychiatrist/primatologist Alfonso Troisi proposed that displacement activities can be used as non-invasive measures of stress in primates. He noted that various non-human primates perform self-directed activities such as grooming and scratching in situations likely to involve anxiety and uncertainty, and that these behaviours are increased by anxiogenic drugs and reduced by anxiolytic drugs. In humans, he noted that similar self-directed behaviour, together with aimless manipulation of objects, can be used as indicators of 'stressful stimuli and may reflect an emotional condition of negative affect'.
History
The subsequent development of research on displacement activities was a direct consequence of Konrad Lorenz's works on instincts. However, the first mentions of the phenomenon came in 1940 by the two Dutch researchers Nikolaas Tinbergen and Adriaan Kortlandt. Tinbergen in 1952 noted, for example, that 'two skylarks engaged in furious combat suddenly peck at the ground as if they were feeding', or birds on the point of mating may suddenly begin to preen themselves. Tinbergen adopted the term 'displacement activities' because the behaviour appeared to be displaced from one behavioural system into another. In 1902, in 'The Little White Bird', J M Barrie refers to sheep in Kensington Gardens nibbling the grass in nervous agitation immediately after being shorn, and to Solomon, the wise crow, drinking water when he was frustrated and outwitted in an argument with other birds. Another bird encourages him to drink in order to compose himself. These references to displacement activities in a work of literature indicate that the phenomenon was well recognized at the turn of the twentieth century. A further early description of a displacement activity is by Julian Huxley in 1914.
