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Farm animals housed in close confinement often engage in activities that do not occur with animals maintained in traditional and more complex environments. Many of these activities consist of species-typical motor patterns directed towards unsuited or inappropriate objects, or performed as vacuum activities. For example, piglets fed from a trough from day 2 to day 21 after parturition display much nosing. of penmates and ear sucking (DeBoer and Hurnik 1984). Similarly, confined veal calves in crates may lick their pelage excessively, or, when housed in groups, may suck the naval area of penmates; laying hens and broilers often engage in feather pecking and cannibalism. A list of reports in the literature concerning such behavior is given in Fox (1984). These behaviors are not adaptive, that is, they do not contribute to species-typical development, maintenance, or reproduction and they may even result in physical damage to the performer or its pen- or cagemates (Tschanz 1982). It is widely agreed that the occurrence of these abnormal behaviors is indicative of environmental inadequacy and animal suffering (Sambraus 1981; Fox 1984). Because abnormal behavior is believed to be an important criterion in evaluating animal housing systems and management practices, there is a need for a general concept of behavioral abnormality in farm animals that would facilitate making judgments about the acceptability of given production systems, and to predict effects of environmental changes on animal welfare (Duncan 1983).

This paper contributes to the development of a concept of behavioral abnormality by comparing the situation of animals in an artificial environment to an experimental learning situation. The concept is based on behavioristic theory developed by Seligman (1970) and Staddon and Simmelhag (1971 ). The concept provides a novel perspective of behavioral normality and abnormality.