Wemelsfelder, F. 1993. The concept of animal boredom and its relationship to stereotyped behaviour. In: Stereotypic Animal Behaviour: Fundamentals and Applications to Animal Welfare. Lawrence, A. B. , Rushen, J. (eds), 65-97. CAB International, Wallingford.
It was argued that the abnormal, disintegrated character of stereotyped behaviour provides direct evidence of suffering. I propose that the gradual impairment of an animal's ability to interact with the environment may be conceived as boredom in the early stages of impairment and as depression and/or anxiety in later, more severe stages of impairment. ... These stages .. may be designated as frustration. .. Frustration may be the predominant form of suffering in the early stages of behavioural fixation, when stereotyped patterns are not yet established. .. Boredom may be defined as that stage of behavioural fixation in which the animal's orientation towards a novel stimulus loses its inquisitive and manipulative character. .. Stereotyped and apathetic behaviour may be interpreted as depression. .. .. I suggest that animals experience an environment as ;monotonous', that is remaining endlessly the same, when the environment does not provide sufficient opportunities for behavioural interaction. 'Monotony' is thus defined as a parameter of the animal-environment relationship , and not as a trait of the physical environment by itself.