Emotions in farm animals:: a new approach to animal welfare in applied ethology
Introduction
Animal welfare is becoming a major topic in applied ethology. Applied ethology deals with behaviour of animals reared by humans. Humans, being responsible for the living conditions of the animals, have the duty to ensure minimal welfare standards. For example, the Council of Europe adopted a Convention for the protection of animals kept for farming purposes in 1976 (Council of Europe, 1976). The concern for animal welfare is strongly associated with the attribution of mental states to animals (Dawkins, 1990). Welfare is fulfilled when the animals do not feel any long lasting negative emotions and when they can experience positive emotions (Dawkins, 1983, Fraser, 1995). Nevertheless, what emotions exactly farm animals can feel is not clear.
Emotional responses are generally assessed by behavioural tests, which are often experimentally using events that animals can face in farming. For example, Hargreaves and Hutson (1990) studied the emotional response of wethers in five routine handling treatments namely shearing, crutching, drenching, dipping and drafting. In such tests, the tendency of an animal to react more or less to negative events is called ‘emotionality’ or ‘reactivity’ or so-called ‘temperament’ (Wolff et al., 1997, Boissy, 1998). Emotional states are used as post-hoc variables to try to understand the animal's reaction to the test. Words like ‘fear’ or ‘frustration’ are often used to describe what the animal experiences when faced with a new or sudden situation, or one associated beforehand with punishment (Gray, 1987). Hence, fear is highly adaptive, it prevents the animal from interacting with potentially dangerous elements. The term of frustration describes the emotional state arising when the animal fails to achieve some gratification where it is expected (LeDoux, 1995). Exposure to sudden stimuli, to the presence of a human or a novel object or environment are classically used to induce fear in order to study the effect of breed or rearing conditions on reactivity of animals from various species, such as sheep (Romeyer and Bouissou, 1992) and cattle (Boissy and Bouissou, 1995). In addition, preventing the access to a substrate that allows performance of highly motivated behaviour results in emotional responses, which are believed to express frustration. For instance, Mason et al. (2001) used the word ‘frustration’ to explain the increased cortisol blood levels in minks denied the access to a pool where they used to swim. But in most other cases, tests are not set up to address the question of emotions of animals and no comparison between different emotional states can be made.
In behavioural tests, the measures are mainly based on ‘gross’ behaviour: approach or avoidance of a stimulus, locomotion during a test, interaction with an object or a person are generally measured (Boissy et al., 2001). These might not allow us to distinguish between different emotions. For example, locomotor activity of sheep is increased in fear eliciting situations such as the presence of a novel object or in an open-field (Romeyer and Bouissou, 1992). However, locomotor activity is also enhanced in response to a sexually frustrating situation (Bishop et al., 1999). In humans, emotions can be distinguished via facial expressions even when the general behaviour of the person looks the same (Ekman and Friesen, 1971). Because the aim of most experiments related to emotions in farm animals was to characterise their ‘reactivity’, such distinctions are not looked for.
Although it is claimed that farm animals are sentient creatures, it is paradoxical that there is no exact knowledge of what their subjective experiences are about. This gap in knowledge could result from a lack of a theoretical framework for the study of emotions in animals. Recent developments in human psychology could help us to overcome this problem. In this paper, we first present a series of arguments in favour of the existence of emotions in farm animals. On the basis of current knowledge, we show that these animals are able to build mental representations to support their subjective experiences. Then, after a brief presentation of the different theories of emotion developed in human psychology, we propose a framework for an approach of emotions in animals. This paper will focus on birds and mammals, which are used in farming, and which will be referred to as ‘farm animals’.
Section snippets
Existence of emotional experiences in animals
An emotion is an intense but short-living affective response to an event (the duration of emotion is a much debated question but briefness seems widely accepted), and is materialised in specific body changes. An emotion is classically described through a behavioural component (a posture or an activity), an autonomic component (visceral and endocrine responses) and a subjective component (emotional experience or feeling) (for review see Dantzer, 1988). In addition, the subjective component,
Diversity of approaches of emotion in psychology
Emotions have been extensively studied in psychology. A brief review of this wide research could help to clarify what emotion is and may be useful to develop further studies of animal emotions. The range of emotions experienced by humans was reported long ago, and several classifications have since been proposed. Around the beginning of the 20th century, the opposition between the ‘peripheralists’ like James, and the ‘centralists’ like Cannon rekindled interest in the study of emotions in human
The relevance of appraisal theories for the study of animals' emotions
In this section, we propose an operational framework to analyse objectively the types of emotions that are accessible to animals. To this point, we focused on the appraisal processing that the animal may undertake in response to an eliciting situation. The framework that will be proposed finds its roots in the cognitive theories of emotions, especially the approach developed by Scherer, 1984a, Scherer, 2001. However, some points have to be discussed in the light of the information available on
Conclusion
There is evidence that animals used for farming purposes feel emotions. However, classical measurements used to evaluate emotions in animals are generally based on a linear scale on which responsiveness of the animal is estimated. For instance, animals are characterised as more or less fearful (Vandenheede and Bouissou, 1993, Rekilä et al., 1997, Jones and Hocking, 1999). Two dimensions are sometimes taken into account as proposed by Bohus et al. (1987) who describe animals as passive versus
Acknowledgements
The authors are greatly indebted to Robert Dantzer and Klaus Scherer for having drawn our attention on psychological theories of emotions and for their stimulating advise during the writing of the present paper. We also thank Claudia Terlouw for correcting the English of the manuscript.
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