Emotion in animals
is defined as any mental experience with high intensity and high hedonic content. The existence and nature of emotions in non-human animals are believed to be correlated with those of humans and to have evolved from the same mechanisms. Charles Darwin was one of the first scientists to write about the subject, and his observational approach has since developed into a more robust, hypothesis-driven, scientific approach. Cognitive bias tests and learned helplessness models have shown feelings of optimism and pessimism in a wide range of species, including rats, dogs, cats, rhesus macaques, sheep, chicks, starlings, pigs, and honeybees. Jaak Panksepp played a large role in the study of animal emotion, basing his research on the neurological aspect. Mentioning seven core emotional feelings reflected through a variety of neuro-dynamic limbic emotional action systems, including seeking, fear, rage, lust, care, panic and play. Through brain stimulation and pharmacological challenges, such emotional responses can be effectively monitored.
Emotion has been observed and further researched through multiple different approaches including that of behaviourism, comparative, anecdotal, specifically Darwin's approach and what is most widely used today the scientific approach which has a number of subfields including functional, mechanistic, cognitive bias tests, self-medicating, spindle neurons, vocalizations and neurology.
While emotions in nonhuman animals is still quite a controversial topic, it has been studied in an extensive array of species both large and small including primates, rodents, elephants, horses, birds, dogs, cats, honeybees and crayfish.
Etymology, definitions, and differentiation
The word "emotion" dates back to 1579, when it was adapted from the French word émouvoir, which means "to stir up". However, the earliest precursors of the word likely date back to the very origins of language.Emotions have been described as discrete and consistent responses to internal or external events which have a particular significance for the organism. Emotions are brief in duration and consist of a coordinated set of responses, which may include physiological, behavioural, and neural mechanisms. Emotions have also been described as the result of evolution because they provided good solutions to ancient and recurring problems that faced ancestors.
Laterality
It has been proposed that negative, withdrawal-associated emotions are processed predominantly by the right hemisphere, whereas the left hemisphere is largely responsible for processing positive, approach-related emotions. This has been called the "laterality-valence hypothesis".Basic and complex human emotions
In humans, a distinction is sometimes made between "basic" and "complex" emotions. Six emotions have been classified as basic: anger, disgust, fear, happiness, sadness and surprise. Complex emotions would include contempt, jealousy and sympathy. However, this distinction is difficult to maintain, and animals are often said to express even the complex emotions.Background
Behaviourist approach
Prior to the development of animal sciences such as comparative psychology and ethology, interpretation of animal behaviour tended to favour a minimalistic approach known as behaviourism. This approach refuses to ascribe to an animal a capability beyond the least demanding that would explain a behaviour; anything more than this is seen as unwarranted anthropomorphism. The behaviourist argument is, why should humans postulate consciousness and all its near-human implications in animals to explain some behaviour, if mere stimulus-response is a sufficient explanation to produce the same effects?Some behaviourists, such as John B. Watson, claim that stimulus–response models provide a sufficient explanation for animal behaviours that have been described as emotional, and that all behaviour, no matter how complex, can be reduced to a simple stimulus-response association. Watson described that the purpose of psychology was "to predict, given the stimulus, what reaction will take place; or given the reaction, state what the situation or stimulus is that has caused the reaction".
The cautious wording of Dixon exemplifies this viewpoint:
Moussaieff Masson and McCarthy describe a similar view :
Because of the philosophical questions of consciousness and mind that are involved, many scientists have stayed away from examining animal and human emotion, and have instead studied measurable brain functions through neuroscience.
Comparative approach
In 1903, C. Lloyd Morgan published Morgan's Canon, a specialised form of Occam's razor used in ethology, in which he stated:Darwin's approach
initially planned to include a chapter on emotion in The Descent of Man but as his ideas progressed they expanded into a book, The Expression of the Emotions in Man and Animals. Darwin proposed that emotions are adaptive and serve a communicative and motivational function, and he stated three principles that are useful in understanding emotional expression: First, The Principle of Serviceable Habits takes a Lamarckian stance by suggesting that emotional expressions that are useful will be passed on to the offspring. Second, The Principle of Antithesis suggests that some expressions exist merely because they oppose an expression that is useful. Third, The Principle of the Direct Action of the Excited Nervous System on the Body suggests that emotional expression occurs when nervous energy has passed a threshold and needs to be released.Darwin saw emotional expression as an outward communication of an inner state, and the form of that expression often carries beyond its original adaptive use. For example, Darwin remarks that humans often present their canine teeth when sneering in rage, and he suggests that this means that a human ancestor probably utilized their teeth in aggressive action. A domestic dog's simple tail wag may be used in subtly different ways to convey many meanings as illustrated in Darwin's The Expression of the Emotions in Man and Animals published in 1872.
Anecdotal approach
Evidence for emotions in animals has been primarily anecdotal, from individuals who interact with pets or captive animals on a regular basis. However, critics of animals having emotions often suggest that anthropomorphism is a motivating factor in the interpretation of the observed behaviours. Much of the debate is caused by the difficulty in defining emotions and the cognitive requirements thought necessary for animals to experience emotions in a similar way to humans. The problem is made more problematic by the difficulties in testing for emotions in animals. What is known about human emotion is almost all related or in relation to human communication.Scientific approach
In recent years, the scientific community has become increasingly supportive of the idea of emotions in animals. Scientific research has provided insight into similarities of physiological changes between humans and animals when experiencing emotion.Much support for animal emotion and its expression results from the notion that feeling emotions does not require significant cognitive processes, rather, they could be motivated by the processes to act in an adaptive way, as suggested by Darwin. Recent attempts in studying emotions in animals have led to new constructions in experimental and information gathering. Professor Marian Dawkins suggested that emotions could be studied on a functional or a mechanistic basis. Dawkins suggests that merely mechanistic or functional research will provide the answer on its own, but suggests that a mixture of the two would yield the most significant results.
Functional
Functional approaches rely on understanding what roles emotions play in humans and examining that role in animals. A widely used framework for viewing emotions in a functional context is that described by Oatley and Jenkins who see emotions as having three stages: appraisal in which there is a conscious or unconscious evaluation of an event as relevant to a particular goal. An emotion is positive when that goal is advanced and negative when it is impeded action readiness where the emotion gives priority to one or a few kinds of action and may give urgency to one so that it can interrupt or compete with others and physiological changes, facial expression and then behavioural action. The structure, however, may be too broad and could be used to include all the animal kingdom as well as some plants.Mechanistic
The second approach, mechanistic, requires an examination of the mechanisms that drive emotions and search for similarities in animals.The mechanistic approach is utilized extensively by Paul, Harding and Mendl. Recognizing the difficulty in studying emotion in non-verbal animals, Paul et al. demonstrate possible ways to better examine this. Observing the mechanisms that function in human emotion expression, Paul et al. suggest that concentration on similar mechanisms in animals can provide clear insights into the animal experience. They noted that in humans, cognitive biases vary according to emotional state and suggested this as a possible starting point to examine animal emotion. They propose that researchers may be able to use controlled stimuli which have a particular meaning to trained animals to induce particular emotions in these animals and assess which types of basic emotions animals can experience.
Cognitive bias test
A cognitive bias is a pattern of deviation in judgment, whereby inferences about other animals and situations may be drawn in an illogical fashion. Individuals create their own "subjective social reality" from their perception of the input. It refers to the question "Is the glass half empty or half full?", used as an indicator of optimism or pessimism.To test this in animals, an individual is trained to anticipate that stimulus A, e.g. a 20 Hz tone, precedes a positive event, e.g. highly desired food is delivered when a lever is pressed by the animal. The same individual is trained to anticipate that stimulus B, e.g. a 10 Hz tone, precedes a negative event, e.g. bland food is delivered when the animal presses a lever. The animal is then tested by being played an intermediate stimulus C, e.g. a 15 Hz tone, and observing whether the animal presses the lever associated with the positive or negative reward, thereby indicating whether the animal is in a positive or negative mood. This might be influenced by, for example, the type of housing the animal is kept in.
Using this approach, it has been found that rats which are subjected to either handling or tickling showed different responses to the intermediate stimulus: rats exposed to tickling were more optimistic. The authors stated that they had demonstrated "for the first time a link between the directly measured positive affective state and decision making under uncertainty in an animal model".
Cognitive biases have been shown in a wide range of species including rats, dogs, rhesus macaques, sheep, chicks, starlings and honeybees.