Animal sentience studies look at nonhuman animals’ ability to have positive and negative experiences. At the most basic level, positive and negative experiences are pain and pleasure, but they can also include psychological states of suffering and joy.
Where there is sentience there must also be consciousness. This is because sentience, the ability to feel pleasure and pain, requires consciousness. Pleasure and pain are things that we are conscious of. Because of this close relationship between consciousness and sentience, the terms animal sentience and animal consciousness are virtually synonymous. Studies related to animal consciousness are often sentience studies, because indicators of sentience are something we can observe.
The study of animal sentience is not yet a mature field of study. As noted in the text on what beings are conscious, we do not at present know exactly what a creature must possess in order to be able to feel pain. Today we do know that certain regions in the nervous systems of animals play an essential role in giving rise to painful and pleasurable experiences. We also know the ways some of these regions function and interact. For example, we understand the mechanisms underlying pain transmission.1 But no one knows how a centralizing organ in a nervous system has to be built in order to give rise to a consciousness that can feel that pain. And this is the key question.
It’s not just that we don’t know much about the problem of consciousness. We also don’t know how hard it will be to solve it. But the crucial issue is that there is too little effort put into solving it, and too little awareness of the need for such an effort.
Animal sentience has received very limited study. In recent years the topic has attracted more attention, not so much out of moral concern for nonhuman animals, but instead as a byproduct of the research conducted on the problem of human consciousness.
We can see how limited the study of this issue really is by comparing it to the attention given to the different but related topic of animal cognition. Animal cognition is the study of the intellectual capacities of nonhuman animals. We know much more about it than we do about animal sentience.
Many nonhuman animals have the ability to deal with concepts, including complex and abstract ones. A concept is a kind of mental container or category under which we include impressions that we perceive or ideas that we construct from those impressions. A creature with the ability to form concepts can reason and have beliefs. We don’t yet know if a creature could have beliefs without the ability to form concepts.
Animals that have this ability include, but are not limited to, mammals and birds. As shown by Donald Griffin, who pioneered the study of cognitive ethology (the study of animal cognition based on observation of animal behavior), many other animals also have this ability.2 One of the phenomena on which we base this conclusion is animal communication. An example of this is the communication that occurs between bees when they tell each other the location of flowers with pollen. If bees are conscious, the most plausible explanation of their behavior would be that they understand and use concepts.
The reason that studies of the minds of human beings and especially of other animals have focused on issues other than the simple possession of consciousness is due to a number of speciesist prejudices. Other issues have been perceived as more interesting because of the lack of importance given to sentience. This neglect is present largely due to the fact that sentience hasn’t been recognized as the relevant property for determining moral status. As is explained in the section on the arguments for and against speciesism, it is often assumed that what matters for moral consideration is having certain complex cognitive capacities. Yet that section shows the reasons to conclude that consciousness should be the only relevant criterion. It seems that the idea that complex capacities are more important than consciousness has played a role in focusing on the former rather than the latter.
However, the implications of possession of consciousness is a more fundamental issue than the possession of simple cognition. As shown in the section on the relevance of sentience, the question that matters when deciding whether someone deserves our concern is whether the being is conscious, and not whether the being has certain intellectual abilities.
This does not mean that studies of animal cognition are not useful at all. The possession of certain intellectual capacities provides evidence for consciousness. In addition, showing that there are nonhuman animals with capacities that are often regarded as uniquely human shows that anthropocentric assumptions about humankind’s eminence are unfounded and rooted in speciesist prejudice. This revelation might be helpful — again, indirectly — in helping us to reexamine our speciesist assumptions by showing some of the beliefs we have which are probably wrong yet tend to remain unexamined.
The two advantages highlighted above, however, must be weighed against a great many disadvantages. Animal cognition research is a diversion of our attention in several ways.
First, the indirect benefits of greater knowledge of animal sentience, and the potential for challenging speciesism, are greatly reduced because the studies focus on cognition instead of consciousness.
Second, emphasizing cognition over consciousness may give the impression that what matters morally is not consciousness as such, but the possession of certain cognitive abilities. As a consequence, a wide range of common views that reinforce anthropogenic speciesist prejudice would be reaffirmed, such as that only the possession of human-like states of consciousness is morally relevant.
Finally, there is an issue that cannot be ignored. Research on animal cognition is often performed in ways that harm animals used in research. Research on animal consciousness may also be done in ways that harm animals. If we reject speciesism, we should oppose this research if we would oppose similar research on human subjects.
Research in this area can, however, be conducted by non-invasive methods. One example is Antonio Damasio’s research at the University of Iowa, which has studied how consciousness is affected in human subjects who have suffered various types of lesions. This research has yielded greater knowledge about how the brain gives rise to conscious experience.3
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1 In fact, nociception and pain have been studied mainly by using nonhuman animals in laboratories. For a detailed report on pain perception, listing more than 670 references, see Le Bars, D.; Gozariu, M. & Cadden, S. W. (2001) “Animal models of nociception”, Pharmacological Reviews, 53, pp. 597-652 [accessed on 21 February 2013].
2 See in particular Griffin, D. R. (1981) The question of animal awareness: Evolutionary continuity of mental experience, New York: Rockefeller University Press; (1984) Animal thinking, Cambridge: Harvard University Press; (1992) Animal minds, Chicago: University of Chicago Press.
3 Damasio, A. R. (1994) Descartes’ error: Emotion, reason, and the human brain, New York: Avon; (1999) The feeling of what happens: Body and emotion in the making of consciousness, San Diego: Harcourt; (2003) Looking for Spinoza: Joy, sorrow, and the feeling brain, Orlando: Harvest.