Imprinting (psychology)  In psychology and ethology, imprinting is any kind of phase-sensitive learning (learning occurring at a particular age or a particular life stage) that is rapid and apparently independent of the consequences of behaviour. It was first used to describe situations in which an animal or person learns the characteristics of some stimulus, which is therefore said to be "imprinted" onto the subject. Imprinting is hypothesized to have a critical period. The best-known form of imprinting is "filial imprinting", in which a young animal narrows its social preferences to an object (typically a parent) as a result of exposure to that object. It is most obvious in nidifugous birds, which imprint on their parents and then follow them around. It was first reported in domestic chickens, by Sir Thomas More in 1516 as described in his treatise Utopia, 350years earlier than by the 19th-century amateur biologist Douglas Spalding. It was rediscovered by the early ethologist Oskar Heinroth, and studied extensively and popularized by his disciple Konrad Lorenz working with greylag geese. Lorenz demonstrated how incubator-hatched geese would imprint on the first suitable moving stimulus they saw within what he called a "critical period" between 13–16 hours shortly after hatching. For example, the goslings would imprint on Lorenz himself (to be more specific, on his wading boots), and he is often depicted being followed by a gaggle of geese who had imprinted on him. Lorenz also found that the geese could imprint on inanimate objects. In one notable experiment, they followed a box placed on a model train in circles around the track. Filial imprinting is not restricted to non-human animals that are able to follow their parents, however. The filial imprinting of birds was a primary technique used to create the movie "Winged Migration" ("Le Peuple Migrateur"), which contains a great deal of footage of migratory birds in flight. The birds imprinted on handlers, who wore yellow jackets and honked horns constantly. The birds were then trained to fly along with a variety of aircraft, primarily ultralights. The Italian hang-glider pilot Angelo d'Arrigo extended this technique. D'Arrigo noted that the flight of a non-motorised hang-glider is very similar to the flight patterns of migratory birds; both use updrafts of hot air (thermal currents) to gain altitude that then permits soaring flight over distance.