15/01/2014

Emotion in animals*

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There is scientific evidence supporting the claim that non-human animals can feel emotions and that human emotions evolved from the same mechanisms.
In recent years, research has become available which expands prior understandings of animal language, cognition, tool use, and sexuality.

Darwin's perspective:

Charles Darwin 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 Emotion in Man and Animals.[4] 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.

Basic emotions vs. Complex human emotions:

A distinction is sometimes made between "basic" emotions such as fear and anger, and "complex" human emotions such as jealousy and sympathy. However, this distinction is difficult to maintain, and animals are often said to express even the complex emotions.

Evidence:

While humans have had differing views of animal emotion, the scientific examination of animal emotion has led to little information beyond a recognition that animals have the capacity for pain, fear, and such responses as are needed for survival. Historically, prior to the rise of sciences such as ethology, interpretation of animal behaviour tended to favour a kind of minimalism known as behaviourism, in this context the refusal to ascribe to an animal a capability beyond the least demanding that would explain a behaviour; anything more than this was seen as unwarranted anthropomorphism. Put crudely, 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?
The cautious wording of Beth Dixon's 2001 paper on animal emotion exemplifies this viewpoint:
Recent work in the area of ethics and animals suggests that it is philosophically legitimate to ascribe emotions to non-human animals. Furthermore, it is sometimes argued that emotionality is a morally relevant psychological state shared by humans and non humans. What is missing from the philosophical literature that makes reference to emotions in non-human animals is an attempt to clarify and defend some particular account of the nature of emotion, and the role that emotions play in a characterization of human nature. I argue in this paper that some analyses of emotion are more credible than others. Because this is so, the thesis that humans and nonhumans share emotions may well be a more difficult case to make than has been recognized thus far.
Jeffrey Moussaieff Masson describes a similar view (with which he disagrees):
While the study of emotion is a respectable field, those who work in it are usually academic psychologists who confine their studies to human emotions. The standard reference work, The Oxford Companion to Animal Behavior, advises animal behaviourists that "One is well advised to study the behaviour, rather than attempting to get at any underlying emotion."
There is considerable uncertainty and difficulty related to the interpretation and ambiguity of emotion: an animal may make certain movements and sounds, and show certain brain and chemical signals when its body is damaged in a particular way. But does this mean an animal feels—is aware of—pain as we are, or does it merely mean it is programmed to act a certain way with certain stimuli? Similar questions can be asked of any activity an animal (including a human) might undertake, in principle. Many scientists regard all emotion and cognition (in humans and animals) as having a purely mechanistic basis.
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.

General evidence:

Evidence for emotions in animals has been primarily anecdotal, coming from individuals who interact with pets on a regular basis. However, critics of emotions in animals cite anthropomorphism as motivating factor in the above suggestion. Much of the debates confusion centers around the difficulty in defining emotion and the cognitive requirements necessary to experience emotion in a similar vein to humans.[8] The problem is also furthered by the difficulty in testing for emotion in animals. What is known about human emotion is almost all related or in relation to human communication.
Recent attempts in studying emotion in animals have led to new constructions in experimental and information gathering. Mariann Dawkins suggested that emotions could be studied through a functional lens or a mechanistic lens. Functional approaches would rely on understanding what roles emotions play in humans and examining that role in non-human animals. Oatley and Jenkins promote a 3 stage structure to emotion which encompasses a broad range of possibility. The structure, however, may be too broad and could be used to include all the animal kingdom as well as certain plants. The second approach, mechanistic, requires an examination of the mechanisms that drive emotion and search for similarities in non-human 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. Observation of the mechanisms that function in human emotion expression, Paul et al suggest that concentration on similar mechanisms in non-human animals can provide clear insights into the animal experience. Paul suggests that cognitive biases vary according to emotional state and suggest this as a possible starting point to examine animal emotion. They propose that researchers may be able to use a controlled stimuli that have accounted appraisal criteria to induce particular emotions in animals and gather which types of basic emotions non-human animals can experience.
Dawkins suggests that merely mechanistic or functional research will provide the answer on its own and suggests that a mixture of the two would yield the most significant results.

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For animal emotion:

In recent years, the scientific community has become increasingly supportive of the idea of emotions in animals. Prior to scientific support, evidence for animal emotion was based on anecdotal evidence provided from individuals who had frequent contact with animals. Recent scientific research has provided insight into similarities of physiological changes between human and non-human animals when experiencing emotion.
Darwin concluded, through a survey, that humans share universal emotive expressions and suggested that animals likely share in these to some degree. Darwin's results have come under fire by individuals that suggest misinterpretations. Social constructivists disregard the concept that emotions are universal. Others hold an intermediate stance, suggesting that basic emotional expressions and emotion are universal but the intricacies are developed culturally. A study by Elfenbein and Ambady (2002) suggested that individuals within a particular culture are better at reading other cultural members emotions. Most support for animal emotion and it's expression results from the notion that feeling doesn't require significant cognitive processes. Animals would not likely need to employ a significant amount of cognitive processes in order to have emotion, rather, they could be motivated by the processes to act in an adaptive way, as suggested by Darwin.

Against animal emotion:

Animal emotion is often rejected due to lack of evidence and those that don't submit to the idea of animal intelligence often cite that anthropomorphism plays a significant role in individuals' perspectives. Those who reject animal's capacity to have emotion mainly do so by citing inconsistencies in studies that have endorsed animal emotion. Having no direct means to communicate emotion, the difficulty of providing an account of emotion in animals relies heavily on work-around experimentation that relies on results from human subjects. Those opposing the concept of animal emotion suggest that emotions aren't universal, including in humans. That emotions are not universal would suggest that there is not a phylogenetic relationship between human and animal emotion. The relationship drawn by proponents of animal emotion, then, would be merely a suggestion of mechanistic features that promote adaptivity but lack the complexity of human emotion constructs. Elaborating further on this idea, it's possible that emotions are basic that have been developed from a social construct.
Opponents also critique the lack of a precise definition of the term emotion. At times, the term is defined too loosely and includes plants. By not having a sturdy framework, studies in animal emotion cannot verify their results and oftentimes anthropomorphise animals beyond their actual capacities.

Specific evidence:

Primates:

Further information: Great ape personhood and Primate cognition
Primates and in particular great apes are candidates for highly developed capabilities for empathy and theories of mind. Great apes have highly complex social systems. Young apes and their mothers have very strong bonds of attachment. Often when a baby chimpanzee or gorilla dies, the mother will carry the body around for several days. Jane Goodall has described chimpanzees as exhibiting mournful behavior. See notably the example of the gorilla Koko, who expressed sadness over the death of her pet cat, All Ball.
Beyond such anecdotal evidence, strong support for empathetic reactions has come from studies of rhesus macaques. In studies by Wechkin et al. and Masserman et al., these macaques refused to pull a chain that delivered food to themselves if doing so shocked a companion. This inhibition to hurt another was more pronounced between familiar than unfamiliar macaques, a finding similar to that of empathy in humans.
Moreover, there has been a good deal of research conducted on consolation behavior in chimpanzees. De Waal and Aureli found that third-party contacts attempt to relieve the distress of contact participants by consoling (e.g. making contact, embracing, grooming, etc.) recipients of aggression, especially those that have faced more intense aggression. Interestingly, researchers were unable to replicate these results using the same observation protocol in studies of monkeys, demonstrating a possible difference inempathy between monkeys and apes.
Finally, some studies have examined emotional processing in the great apes. Specifically, chimpanzees were shown video clips of emotionally charged scenes, such as a detested veterinary procedure or a favorite food, and then were required to match these scenes with one of two species-specific facial expressions: “happy” (a play-face) or “sad” (a teeth-baring expression seen in frustration or after defeat). The chimpanzees correctly matched the clips to the facial expressions that shared their meaning, demonstrating that they understand the emotional significance of their facial expressions. Measures of peripheral skin temperature confirmed that the video clips emotionally affected the chimpanzees.

Rodents:

Jaak Panksepp proposed that all mammalian species are equipped with brains capable of generating emotional experiences. In a more recent article, he examines rodentstudies conducted from individuals in the C57 line in order to provide foundational support for this claim. One such study, conducted by Rice and Gainer, examined whether ratswould work to alleviate the distress of a conspecific. Rats were trained to press a lever to avoid the delivery of a shock, signaled by a visual cue, to a conspecific. They were then tested in a situation in which a conspecific was hoisted into the air, or a Styrofoam block in the control group, and could be lowered with the press of a lever. Rats that had previous experience with conspecific distress demonstrated greater than ten-fold more responses to lower a distressed conspecific compared to rats in the control group, while those who had never experienced conspecific distress expressed greater than three-fold more responses to lower a distressed conspecific relative to the control group. This suggests that rats will actively work to reduce the distress of a conspecific, a phenomenon related to empathy. Comparable results have also been found in similar experiments designed for monkeys.
Also relevant, Langford et al. examined empathy in rodents using an approach based in neuroscience. They found that (1) if two mice experienced pain together they expressed greater levels of pain-related behavior than if pain was experienced individually, (2) if experiencing different levels of pain together, the behavior of each mouse was modulated by the level of pain experienced by its social partner, and (3) sensitivity to a noxious stimulus was experienced to the same degree by the mouse observing a conspecific in pain as it was by the mouse directly experiencing the painful stimulus. The authors suggest this responsiveness to the pain of others demonstrated by mice is indicative of emotional contagion, a phenomenon associated with empathy.
Several studies have also shown rodents can respond to a conditioned stimulus that has been associated with the distress of a conspecific as if it were paired with the direct experience of an unconditioned stimulus. These studies suggest that rodents are capable of shared affect, a concept critical to empathy.

Birds:

The author Marc Bekoff provided evidence of animals having emotions in his book, The Emotional Lives of Animals. The following is an excerpt from his book:
A few years ago my friend Rod and I were riding our bicycles around Boulder, Colorado, when we witnessed a very interesting encounter among five magpies. Magpies are corvids, a very intelligent family of birds. One magpie had obviously been hit by a car and was laying dead on the side of the road. The four other magpies were standing around him. One approached the corpse, gently pecked at it-just as an elephant noses the carcass of another elephant- and stepped back. Another magpie did the same thing. Next, one of the magpies flew off, brought back some grass, and laid it by the corpse. Another magpie did the same. Then, all four magpies stood vigil for a few seconds and one by one flew off.

Furthermore, in an observational study, Orlaith and Bugnyar sought to explore bystander affiliation (post-conflict affiliation from an uninvolved bystander to the conflict victim) in ravens. Bystander affiliation has been believed to represent an expression of empathy in which the bystander tries to console the victim and alleviate his/her distress. When examining post-conflict behavior in ravens, Orlaith and Bugnyar found that there was strong evidence for bystander affiliation (e.g. contact sitting, preening, or beak-to-beak or beak-to-body touching) and also for solicited bystander affiliation, in which there is post-conflict affiliation from the victim to the bystander. Solicited bystander affiliation is thought to reduce the likelihood of renewed aggression against the victims. The researchers concluded that ravens may be sensitive to the emotions of others. However, it is important to note that relationship quality plays an important role in the prevalence and function of these post-conflict interactions. More specifically, bystanders involved in both bystander affiliation and solicited bystander affiliation were likely to share a valuable relationship with the victim. This is similar to findings regarding empathy in humans and non-human primates, in which degree of familiarity between social partners influences the occurrence of empathetic acts.

Canines:

Research suggests that canines can experience negative emotions in a similar manner to people, including the equivalent of certain chronic and acute psychological conditions. The classic experiment for this was Martin Seligman's foundational experiments and theory of learned helplessness at the University of Pennsylvania in 1965, as an extension of his interest in depression:
A dog that had earlier been repeatedly conditioned to associate a sound with electric shocks did not try to escape the electric shocks after the warning was presented, even though all the dog would have had to do is jump over a low divider within ten seconds, more than enough time to respond. The dog didn't even try to avoid the "aversive stimulus"; it had previously "learned" that nothing it did mattered. A follow-up experiment involved three dogs affixed in harnesses, including one that received shocks of identical intensity and duration to the others, but the lever which would otherwise have allowed the dog a degree of control was left disconnected and didn't do anything. The first two dogs quickly recovered from the experience, but the third dog suffered chronic symptoms of clinical depression as a result of this perceived helplessness.
A further series of experiments showed that (similar to humans) under conditions of long-term intense psychological stress, around 1/3 of dogs do not develop learned helplessness or long term depression. Instead these animals somehow managed to find a way to handle the unpleasant situation in spite of their past experience. The corresponding characteristic in humans has been found to correlate highly with an explanatory style and optimistic attitude that views the situation as other than personal, pervasive, or permanent.
Since this time, symptoms analogous to clinical depression, neurosis, and other psychological conditions have also been accepted as being within the scope of canine emotion.
In addition, Psychology research has shown that human faces are asymmetrical, with the gaze instinctively moving to the right side of a face upon encountering other humans to obtain information about their emotions and state. Research at the University of Lincoln (2008) shows that dogs share this instinct when meeting a human being, and only when meeting a human being (i.e., not other animals or other dogs). As such they are the only non-primate species known to do so.
Finally, the existence and nature of personality traits in dogs have been studied (15,329 dogs of 164 different breeds) and five consistent and stable "narrow traits" identified, described as playfulness, curiosity/fearlessness, chase-proneness, sociability and aggressiveness. A further higher order axis for shyness–boldness was also identified.

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Felines:

The emotions of cats have also been studied scientifically. It has been shown that cats can learn to manipulate their owners through vocalizations that are similar to the cries of human babies. Some cats learn to add a purr to the cry, which makes it less harmonious and more dissonant to humans, and therefore harder to ignore. Individual cats learn to make these cries through operant conditioning; when a particular cry elicits a positive response from a human, the cat is more likely to use that cry in the future.
Growling can be a sign of annoyance or fear, similar to humans. When annoyed or angry, a cat will wriggle and thump its tail much more vigorously than when in a contented state. In bigger cats like Lions, what is and isn't irritating varies from individual. Male may let his cubs play with his mane or tail, or he may hiss and bat them away. Domestic male cats have varying attitudes towards their offsprings as well.
Older male siblings tend not to go near new ones, and may even show hostility.
The father tom of kittens will tolerate his young for a time, but even he may kill them to drive a female back in heat.

Fish:

A 2007 study by the University of Guelph Scientists in Canada suggests that fish may have their own separate personalities. The study examined a group of trout that were visually identical. The study concluded that different fish within the same group exhibited different personality traits. Some fish were more willing to take risks in unknown waters than others when taken from their environment and introduced to a dark tube. Some fish were more social than others, while some preferred being alone. Fish were also shown to have different preferences as far as eating habits.

Whales:

Hof and Van Der Gucht have found that various types of whales possess the same emotion-producing brain cells as humans. Hof and Van Der Gucht discovered the presence of spindle cells in the anterior cingulate cortex and frontoinsular cortex, the same areas of the brain that regulate emotional functions such as empathy, speech, intuition, rapid “gut reactions,” and social organization in human beings. Additionally, whales have these cells in greater numbers of spindle cells and maintain them for twice as long as humans. Spindle cells are believed to be the cells that make us human. These brain cells allow us to feel emotions such as love and suffering emotions. Scientists originally thought that spindle cells were found only in humans and our closest evolutionary relatives: apes and monkeys. However, Hof clarifies that he does not know the nature of such feelings in these animals. We cannot just apply what we see in great apes or ourselves to whales. He believes that more work is needed to know for sure whether love is the same for humans and whales.
While the exact function of spindle cells in whale brains is still under study, Hof believes that they act as some sort of “high-speed connections that fast-track information to and from other parts of the cortex”. He compared them to express trains that bypass unnecessary connections, enabling organisms to instantly process and act on emotional cues during complex social interactions.

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