Imprinting Versus Learning
The most salient feature of the imprinting phenomenon is its many differences from simple association learning. There is now a wealth of experimental evidence to show that imprinting differs fundamentally from association learning in several respects, and to demonstrate the problems in dealing with behaviors that owe a great deal to genetic factors rather than exclusively to environmental ones.
The first systematic investigations on imprinting were published in 1951. Independently, in this country and in Europe, the work of scientists gave the first indications of some of the important factors in the process. Most of Ramsay’s experiments dealt with exchange of parents and young, although he also imprinted some waterfowl on such objects as a football or a green box. . . .
Our birds (ducks and chicks) were incubated and hatched right in our laboratory. They hatched in the dark, and each animal was placed in an individual box marked with the exact hour at which the animal hatched. The bird, in the box, was kept in a still-air incubator and kept there until it was to be imprinted. After the animal had undergone the imprinting experience, it was returned to the box and kept there until testing. Only after testing was completed was the young bird placed in day light and given food and water.
Although the intensive effort to find and formulate laws of learning (in hopes of accounting for the causal bases of all behaviors) did show that certain behaviors once thought to be instinctive were indeed modifiable by learning, the realization is growing that there are still certain behaviors that are so persistent in character and resistant to modification by reinforcement that they cannot be satisfactorily explained by conventional laws of learning. In such cases, and imprinting is one of them, other explanatory devices must be constructed. He was the first to bring widespread attention to this phenomenon of imprinting, and he gave it its name. In a broad sense, imprinting refers to an early experience that has a pro found influence on the later adult social and sexual behavior of an animal with respect to the choice of objects for these behaviors.
For example, Craig reported Whitman’s unpublished experiments with wild pigeons, in which he found that in order to be able to cross two different pigeon species, he had first to rear the young of one species with foster parents of the other species. After such an upbringing, these animals actually preferred to mate with the other species. Such inter species sexual fixations have been observed since then in other birds, some fishes, and two mammals-the alpaca. The doctor and his wife raised by hand the young of almost every species of European birds, and noted that many of the social responses of these birds were transferred to their human caretaker as a result of this experience. Although imprinting has been studied mainly in birds, it also has been observed in other animals.