Published online by Cambridge University Press: 06 January 2010
In the absence of adult conspecifics, newly-hatched chicks will approach a wide range of bright or moving objects. After a period of exposure to such an object they form a social attachment to it. When they are close to the object the chicks emit soft calls, and if it moves away they will follow it. If subsequently exposed to a new object the chicks will run away emitting distress calls. From these observations it may be inferred that chicks learn about some of the visual characteristics of the first object to which they are exposed. This process is referred to as filial imprinting, and has been studied most intensively in precocial birds such as domestic chicks, ducklings, and goslings (Spalding, 1873; Heinroth, 1911; Lorenz, 1935, 1937; Bateson, 1966). Similar processes may also occur in mammals, but evidence for this is harder to obtain due to their comparative lack of mobility shortly after birth. This chapter will concentrate on the neural and behavioural analysis of filial imprinting in the domestic chick, a species which readily imprints on to a wide range of visual objects.
Imprinting can be reliably reproduced in the laboratory in the following way. Chicks are dark-reared until being exposed to a conspicuous object such as a rotating, illuminated red box, for a period of time, normally several hours. From between two hours to several days later, chicks are given a choice between the object to which they were exposed and a novel object. The extent to which the chick approaches each of the two objects is compared and a preference score calculated.