Table 3.5 Evidence for conscious feelings in non-human animals, classified according to category
| Classification | Definition | Examples of evidence for conscious feelings falling into this category |
| Poor | The behaviour observed is capable of being comprehensively modelled by a third-person account. Some features of the behaviour are evocative of first-person behaviour in human beings, but there is no comprehensive first-person model of the behaviour. Evidential value: None. |
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| Ambiguous | EITHER there is a first-person model for the behaviour observed as well as an alternative third-person model, OR there is a first-person model whose central concepts can be re-interpreted in terms of third-person concepts. The first-person model has no more scope or predictive power than the third-person model. Evidential value: None, unless a new, superior first-person model can be formulated. |
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| Insufficient | Many features of the behaviour are evocative of first-person behaviour in human beings. No complete model of the behaviour exists, but there are general grounds for believing that the behaviour can be adequately explained in third-person terms. Evidential value: None, unless the third-person approach can be effectively undermined. |
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| Mixed | No complete model of the behaviour exists, but there are partial models that can explain selected features of the behaviour. There are partial first-person models which explain those features of the behaviour that are evocative of first-person behaviour in human beings, and there are also partial third-person models of other features that are better understood in mind-neutral terms. Evidential value: Limited. A complete first-person model of the behaviour needs to be developed. |
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| Epistemically uncertain | No complete model of the behaviour exists. The behaviour lends itself to a first-person interpretation, but there is presently not enough information to decide whether a third-person interpretation may also be able to account for the behaviour. Evidential value: Inconclusive. More research needs to be done, to understand the behaviour. |
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| Singular | The behaviour observed is too specific to be described in terms of a general model. However, the behaviour can only be understood if it is interpreted in first-person terms. Evidential value: The evidence may be very persuasive, but it is of no use to scientists until a general model of the behaviour can be formulated. |
Affective behaviour focused at particular individuals:
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| Impressive | A complete first-person model of the behaviour exists, although an alternative third-person interpretation is also possible. The model has certain central features which are unexpected on a third-person interpretation, but would be expected if we envisaged the behaviour in first-person terms. However, the model makes no novel predictions that would rule out a third-person interpretation. Evidential value: Good. However, a more inclusive model needs to be formulated, which makes useful predictions. |
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| Convincing | A complete first-person model of the behaviour exists. The model generates novel predictions that a third-person account fails to make. Evidential value: Good. Scientifically productive. |
Affective disorders:
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So far, our quest for conscious feelings in animals has yielded some tantalising results, but nothing conclusive. In keeping with Conclusion E.4, I shall confine my search to intentional acts. I propose that a subclass of these acts, relating to the hedonic behaviour of animals, are the best place to search for evidence of conscious feelings in animals. However, before we can ascribe feelings to animals, it must be shown that the ascription of feelings allows us to make scientifically useful predictions that a third-person account could not make.
Intoxication and drug addiction
Table 3.6 Behaviours which constitute poor evidence for the existence of conscious feelings in animals
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Kind of Behaviour: Self-stimulation
Description: A laboratory animal with electrodes in its brain has to do something in order to prolong the electrical arousal of its brain's SEEKING system. Alternatively, the animal may have to perform a complicated action (e.g. press a lever) in order to prolong the arousal of its brain's SEEKING system.
Found in which organisms? Self-stimulation has been identified in a wide variety of animals, including fish, crustaceans, and even snails (Panksepp, peronal communication, 30 May 2004).
More complex behaviours have been recorded in rats, who will self-stimulate themselves to death if not prevented from doing so.
Alternative, "third-person" explanation: Maybe the animal is in some automated "do loop", or the instinctual arousal of seeking and the consequent affect keeps the animal magnetised in a repetition compulsion (Panksepp, personal communication, 30 May 2004). |
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Kind of Behaviour: Intoxication
Description:
Many animals seek out intoxicating substances that induce a narcotic state.
Found in which organisms? Beetles, honeybees, crayfish, spiders and fruit flies, as well as mammals.
Examples amenable to a Third-Person explanation: Japanese beetles, for instance, display a preference for the leaves of the geranium plant, and can "pass out" for 12 to 18 hours after feeding on them (Riggs, 2000).
Honeybees will readily consume 20% ethanol solutions, and even stronger solutions of 95% ethanol (so long as the antennae do not make contact with the solution). However, there is no evidence to date of addiction or tolerance (Abramson et al., 2000).
Crayfish which were placed in an aquarium with two kinds of visual environments - a floor and walls with stripes or a floor and walls without stripes - and which received intra-muscular injections of cocaine and/or amphetamines, displayed a conditioned place preference for the environment with similar visual stimuli to the one where they received the injection (Panksepp and Huber, 2004).
Explanation in Third-Person Terminology: Intoxicating substances may be sought because of their chemical resemblance to biologically useful substances: the brain's natural opiates (endorphins).
The pathways oriented to endorphins, sometimes called pleasure centers originated in small organisms such as insects, which rely on the neurological system to help them find familiar sources of food. |
Conclusion E.31 An animal's tendency to engage in self-stimulation does not constitute a sufficient warrant for ascribing conscious feelings of pleasure to it.
Table 3.9 Behaviours which constitute mixed evidence for the existence of conscious feelings in animals
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Kind of Behaviour: Drug addiction
Description:
Many animals seek out intoxicating substances that induce a narcotic state.
Found in which organisms? Beetles, honeybees, crayfish, spiders and fruit flies, as well as mammals.
Examples amenable to a Third-Person explanation: Japanese beetles, for instance, display a preference for the leaves of the geranium plant, and can "pass out" for 12 to 18 hours after feeding on them (Riggs, 2000).
Honeybees will readily consume 20% ethanol solutions, and even stronger solutions of 95% ethanol (so long as the antennae do not make contact with the solution). However, there is no evidence to date of addiction or tolerance (Abramson et al., 2000).
Crayfish which were placed in an aquarium with two kinds of visual environments - a floor and walls with stripes or a floor and walls without stripes - and which received intra-muscular injections of cocaine and/or amphetamines, displayed a conditioned place preference for the environment with similar visual stimuli to the one where they received the injection (Panksepp and Huber, 2004).
Explanation in Third-Person Terminology: Intoxicating substances may be sought because of their chemical resemblance to biologically useful substances: the brain's natural opiates (endorphins).
The pathways oriented to endorphins, sometimes called pleasure centers originated in small organisms such as insects, which rely on the neurological system to help them find familiar sources of food.
Description + Examples Better Construed as First-person Phenomema: In his book, "Intoxication: Life in Pursuit of Artificial Paradise," Ronald K. Siegel, a UCLA psychopharmacologist, describes how many animals will eat fermented fruits, vegetables, plants and other substances that have mind-altering qualities. Siegel noted that the mongoose eats a plant that has psychedelic qualities when grieving over the loss of a mate or when its burrows are destroyed by a monsoon; elephants become intoxicated from eating fermented marula fruit when they are stressed from the thinning of the herd or competition from other animals; and water buffalo have been seen eating poppies. (Source: Researchers Look For Addiction Clues. 3/26/1998. Web address: http://www.jointogether.org/sa/news/reader/0%2C1030%2C24946%2C00.html)
Grounds for preferring a First-person Interpretation: These animals are seeking out intoxicating substances to induce mind-altering euphoria, when they are stressed or sad. The behaviour is likely to be subjective, as it is specific to occasions that would normally induce sadness or anxiety in sentient beings. |
Conclusion E.xx The occurrence of mood-specific drug-seeking behaviour in certain mammals is prima facie evidence that they are capable of feeling conscious pain.
Satiety in animals
The phenomenon of satiety is an interesting one: thirsty human beings who assuage their thirst feel satiated long before their bodies have had time to absorb the water they have imbibed. Denton (1996, 1999) suggests that this phenomenon represents a primal form of consciousness, and speculates that it would have been biologically useful for animals to experience this "full" feeling long before the water they drank had been absorbed into their bodies, so that they could depart from a waterhole as soon as possible, thereby avoiding predators.
Mammals also exhibit the phenomenon of satiety: both rats and humans find sweet liquids less appealing just after a meal than when hungry, and make the same appetitive judgements as humans do, depending on how much sugared water they have drunk: their pattern of changing preferences is indistinguishable from that of people (Vines, 1994). However, satiety in rats and humans may turn out to be explicable in terms of underlying chemical processes.
Conclusion E.33 The phenomenon of satiety need not indicate conscious pleasure in animals.
Trade-offs and Relative Rankings of Goods by Animals
More suggestive is the willingness of animals to make trade-offs whereby they expose themselves for a short time to an aversive stimulus in order to procure some attractive stimulus. Reptiles and mammals - but not amphibians (Cabanac, 2003) are willing to make trade-offs whereby they expose themselves for a short time to an aversive stimulus in order to procure some attractive stimulus. Lizards will leave a warm refuge, where they were supplied with standard food, and venture out into a cold environment, in order to acquire a more palatable food (lettuce) which they do not need. Additionally, they appear to weigh up the relative costs and benefits of their choices: when it gets too cold, the lizards stay in their warm enclosure and eat the nearby food, but if the experimenters improve the quality of the food in the cold corner, the lizards prove willing to tolerate lower temperatures (Cabanac, 2003). Cabanac (2003) concludes that the lizards appear to be making decisions based on palatability, a form of pleasure.
Researchers such as Marian Dawkins (1994) have also found ways of ranking animals' desires for different "goods", by measuring how much they are willing to work (e.g. peck a key) to obtain each good, or alternatively, how much discomfort they are willing to put themselves through in order to obtain various goods. For instance, hens are averse to squeezing through narrow gaps, and even a hungry hen will not squeeze through a 9 centimetre gap to get food, but will readily do so to obtain access to a floor that is suitable for scratching or dust bathing (Vines, 1994).
Cabanac (2003) reports that "all aspects of palatability reported by humans can be found in rats as well, including decision making in conflicts of motivation, palatability vs. cost".
From an economist's perspective, the behaviour described above probably meets the requirements for wanting, as the strength of animals' desires for different goods allows economists to construct utility curves. All that would be needed to complete the picture would be evidence to animals' willingness to exchange one combination of goods for an equally desirable combination.
Since animals' short-term appetitive behaviour is so similar to our own, it would seem churlish to deny the overwhelming behavioural evidence that these animals experience conscious likes and dislikes. However, it has not been shown that a first-person account yields better scientific predictions than a third-person account that employs more neutral terminology. Cabanac himself employs such terminology: the lizards face "conflict between two motivations: a thermoregulatory drive (to avoid cold) and an attraction to palatable bait" (2003).
Conclusion E.xx The willingness of certain kinds of animals to engage in hedonic trade-offs of pain for delayed pleasure constitutes prima facie evidence for conscious feelings on their part.
Rational and irrational pursuit in animals
Researchers working with rats (Berridge, 2001, 2003) have found ways of identifying and isolating both conscious and unconscious features of a rat's liking for sugar, in experiments where the rat has to work (press a lever) in order to obtain a reward - a sugar solution which is infused directly into the rat's mouth. Experienced utility, or the rat's actual liking for an outcome, is assessed by measuring its positive facial reactions (e.g. frequency of tongue protrusions) as it tastes the sugar solution. Remembered utility, or the rat's memory of its liking for an outcome in the past, is measured by its willingness to persist in working for the sugar reward, even under extinction conditions, when the reward no longer comes at all. Predicted utility, or the rat's expected liking for the outcome in the future, is defined as the rat's baseline level of lever pressing when the reward is absent. Finally, the rat's decision utility, or its manifest choice of the outcome, can be defined as as the amount of work it is willing to do in order to obtain the reward. If a rat's dopamine levels are activated by a micro-injection of amphetamine into a region of its brain (the nucleus acumbens), neither the rat's "liking" for the sugar reward (as measured by its positive reaction to the taste of sugar) nor its predicted utility (as measured by its willingness to press the lever when the sugar reward is absent) shows an increase, but when the cue (sugar) is presented to the rat, it engages in a frenzy of pursuit for the reward, which Berridge characterises as irrational pursuit. Berridge explains this not by saying that the dopamine makes the sugar seem more rewarding but by the hypothesis that dopamine increases the sugar's incentive salience.
Berridge's work suggests that wanting and liking are separable psychological processes, and indicates a scientific way of distinguishing between rational and irrational desires in animals. Berridge (2001) defines an animal's choice as rational if its decision utility matches its predicted utility, and its choice maximizes both. That is, an animal chooses rationally if it consistently chooses what it expects to like, even if its expectations happen to be wrong:
[T]he rationality or irrationality of your choice has nothing to do with why you like it, or with whether anyone else likes it too. The question of rationality hinges only on whether your choice consistently follows your expectations of hedonic likes (Berridge, 2001).
Rational pursuit may be manifested when animals are trained to work for real rewards, which come only sporadically, so the animals learn to persist in working for a reward. Under extinction conditions, when the rewards no longer come at all, the animals will keep working for quite some time because they still expect the reward: they have learned that perseverance pays off.
Irrational pursuit, on the other hand, occurs when an animal desires something it neither likes nor expects to like. An animal under the influence of drugs may sometimes choose an outcome whose eventual hedonic value does not justify its choice:
The notion of irrational choice may seem to be self-contradictory when viewed from the perspective that people always choose what has the most value or decision utility to them... However, as documented by a number of authors..., people may sometimes choose an outcome whose eventual hedonic value does not justify their choice...
Irrational pursuit can be identified when an animal, under the influence of some drug (e.g. dopamine), is suddenly presented with the rewarding stimulus, which cues hyperactive pursuit of the stimulus.
Berridge (2001, 2003) presents evidence from human studies that irrational desires need not be conscious: humans can be influenced to like or dislike something simply by subliminal exposure to stimuli which they report beinmg unaware of.
Conclusion E.xx The phenomenon of rational pursuit in animals, which can be mathematically described in terms of four underlying kinds of utility, is suggestive of conscious choice in their part.
Affective distortions
By affective distortions I mean extreme behaviours - such as phobias, intense rage and grief - which can only be explained in terms of the sentient animal's preoccupation with its own feelings. I propose that these affective distortions can serve to identify conscious emotional states. These distortions can be measured scientifically, using insights from Risk Analysis and Decision Theory.
A scientific test for subjectivity?
Consider, for instance, the cliched nineteenth century scenario of two fit young men who engage in a pistol duel in order to win the hand of a woman they both ardently wish to marry. From a purely biological standpoint, a fight to the death is absurdly irrational: each man faces a high probability of dying without leaving any children behind him if he fights, but is still likely to leave a large number of descendants behind if he refrains from duelling and marries someone else. Only if marrying the woman would double each suitor's expected number of descendants would it be biologically "rational" for him to expose himself to a 50% risk of sudden death. In reality, of course, the suitors do not weigh the risks in this way, because they have feelings. Each man mistakenly believes that he will be heartbroken forever if he does not marry the woman, and each confidently believes (buoyed by a false sense of optimism) that his prospect of victory is much greater than 50%.
The foregoing example suggests one way of identifying kinds of behaviour which manifests feelings in animals:
(1) The kind of behaviour in question should not be "hard-wired". In particular, it should satisfy the requirements for one of the four varieties of intentional agency, described in chapter two (see DF. 1 to DF. 4). Roughly speaking, the behaviour is voluntary in the sense that Aristotle would have allowed for animals.(2) The behaviour should be undertaken in pursuit of some goal that the animal might find rewarding (e.g. a dainty morsel of food, or a desirable mate).
(3) The behaviour should be risky to the animal's biological prospects (of leaving descendants).
(4) The biological risks should "outweigh" the biological benefits: the animal can expect to be biologically worse off (as measured by its long-term number of descendants) for engaging in the behaviour.
(5) The behaviour should be systematic - i.e. typical of a species and not just an individual. An individual may behave erratically, but if a species which has evolved for millions of years engages in biologically illogical behaviour, then we have to ask why the behaviour has persisted over time.
If the above conditions are satisfied, then the only sensible explanation for the behaviour is that it is feeling-driven. The reason why the behaviour has not been eradicated would then be that feelings confer survival benefits on their possessors.
Conclusion E.xx Any intentional activity which occurs regularly in animals of a certain species, in which the biological risks outweigh the benefits, constitutes a sufficient warrant for ascribing conscious feelings to animals of that species.
Condition (4) is elaborated in an Appendix, where I explain why I have chosen the long-term number of descendants as a measure of biological rationality of an organism's choice, and set forth the mathematical conditions for a biologically irrational choice.
APPENDIX
Let us consider a class of risky behaviour B, which is found in some species of organism, and which may adversely affect the organism's reproductive prospects. Suppose also that B satisfies the requirements for some form of intentional agency (see Conclusions DF. 1 to DF. 4). Let r be the probability of an adverse effect on the organism's reproductive success. Let E(not-B) be the organism's expected number of progeny if it abstains from behaviour B, E(fail) be the organism's expected number of progeny if it engages in behaviour B and its reproductive prospects are harmed, and E(success) be the organism's expected number of progeny if it engages in behaviour B and its reproductive prospects are enhanced. Then I propose that B manifests phenomenal consciousness if:
E(not-B) > r.E(fail) + (1 - r).E(success).
We can be more precise if we stipulate the number of descendants after N generations. (Allows for considerations of fitness - not all progeny are equal from an evolutionary viewpoint.)