The level of priority and resource given to the care of organisms is influenced by beliefs and understanding about their capacities for conscious awareness. Variation in attitudes to animal welfare around the world today is partly a reflection of this. Improved understanding of the range of phenomena of which animals may be conscious is likely to lead to greater global consensus about the importance of high standards of animal welfare. This is a matter of current relevance. In the global free market there is a danger that efforts in one country to raise standards for farm or laboratory animals will be compromised by competition from others which employ cheaper, less welfare-friendly systems. Scientific developments which inform us about animals’ capacities for pleasant and unpleasant feelings will play an important role in the development of global agreement about animal welfare standards. Deciding which animals might have the capacity for consciousness, and thus for suffering, and of what they might be conscious, are fundamental issues which set boundaries to the ranges of species to be given basic or special forms of welfare protection. In practice, such lines have to be drawn and it is crucial that they are drawn in the right place. This is a difficult but essential task and society looks to scientists for guidance on the matter. There have been many developments in recent years in scientific approaches to the study of consciousness in animals which are pertinent to this debate.

Thinking about animal consciousness is beset with many pitfalls, a few of which are: i) lack of clarity in words used, especially confusing ‘cognition’ with ‘consciousness’ and using words such as ‘emotion’ in both an objective sense (behaviour and physiology) and to imply consciousness; ii) failing to acknowledge sufficiently that different people use different versions of the argument from analogy with ourselves to infer consciousness in non-humans in animals; iii) assuming that choice and preference imply consciousness; iv) assuming that autonomic responses imply consciousness (a particular danger to those who look for physiological ‘measures’ of animal welfare); v) assuming that complexity of behaviour implies complexity of cognition and in turn consciousness; and vi) assuming that only cognitively complex organisms are conscious. Consciousness raises many questions of direct relevance to animal welfare that as yet have no answers, but finding possible answers may be made slightly easier if we avoid these obvious pitfalls.

Recent scientific findings indicate that consciousness is a fundamental biological adaptation. The known brain correlates of consciousness appear to be phylogenetically ancient, going back at least to early mammals. In all mammals, alertness and sensory consciousness are required for the goal-directed behaviours that make species survival and reproduction possible. In all mammals, the anatomy, neurochemistry and electrical activity of the brain in alert states show striking similarities.

After more than seven decades of cumulative discoveries about waking and sensory consciousness, we have not yet found any fundamental differences between humans and other mammals. Species differences such as the size of neocortex seem to be irrelevant to the existence of alertness and sensory consciousness, though different mammals obviously specialize in different kinds of sensory, cognitive and motor abilities.

Sceptics sometimes claim that objective evidence for consciousness tells us little about subjective experience, such as the experience of conscious pain. Scientifically, however, plausible inferences are routinely based on reliable and consistent patterns of evidence. In other humans, we invariably infer subjective experiences from objective behavioural and brain evidence - if someone yells ‘Ouch!’ after striking a finger with a hammer, we infer that they feel pain. The brain and behavioural evidence for subjective consciousness is essentially identical in humans and other mammals. On the weight of the objective evidence, therefore, subjective experience would seem to be equally plausible in all species with human-like brains and behaviour. Either we deny this experience to other humans (which is rarely done) or, to be consistent, we must also attribute it to other species that meet the same objective standards. It seems that the burden of proof for the absence of subjectivity in mammals should be placed on the sceptics.

There are several examples from human neuropsychology of the intact preservation of processes and capacities in the absence of conscious awareness by the patients. These include loss of visual awareness (blindsight), episodic memory (amnesic syndrome), attention (unilateral neglect) and language (aphasia). The implication of these and other clinical phenomena is that descriptions of ongoing behaviour are necessary but quite insufficient for making inferences about conscious awareness, because even quite ‘high level’ behaviour can be run off in the absence of awareness. A commentary, or independent off-line response, is a prerequisite for determining whether the subject is consciously aware. Whether or not the commentary allows an inference about awareness in animals rests ultimately on an argument from analogy, just as is the case when we make judgements about fellow humans. But when parallel disjunctions between on-line behaviour and off-line classifications are found for both human and infrahuman subjects, as is demonstrable for blindsight and amnesia, not only do they bolster inferences about common neural mechanisms, but they strengthen inferences for analogous processing and hence for conscious experience.

This paper will try to answer the question of whether animals can suffer.

My aim is, firstly, to discuss whether or not an irreflexive animal consciousness could experience suffering. I do this because there are authors who assume such a consciousness in animals. The second part of this contribution concerns the question of the cognitive and neural prerequisites which have to be present in order to give consciousness, or the suffering experience, a positive fitness value. Further, I analyse for which animals these brain structures and cognitive capacities have been described, since consciousness and suffering can only be expected in these animals.

In order to answer the questions, several assumptions had to be made. If the assumptions are correct than the results of the various analyses demonstrate that: i) an irreflexive consciousness is unable to experience suffering; and ii) animal suffering may, for the time being, only be expected in the anthropoid apes. However, there is an important difference between the registration of pain as a stimulus, which does not induce feelings of suffering, and the experience of pain as an emotion, which does induce suffering. According to the arguments presented in this contribution, the experience of pain as a stimulus could be expected in far more species than anthropoid apes alone.

The attempt to provide a firm scientific basis for understanding consciousness is now in full swing, with special contributions from two areas. One is experimental: brain imaging is providing ever increasing detail of the brain structures used by humans (and other animals) as they solve a variety of tasks, including those of higher cognition. The other is theoretical: the discipline of neural networks is allowing models of these cognitive processes to be constructed and tested against the available data. In particular, a control framework can be created to give a global view of the brain. The highest cognitive process, that of consciousness, is naturally a target for such experimentation and modelling. This paper reviews available data and related models leading to the central representation, which involves particular brain regions and functional processing. Principles of consciousness, which have great relevance to the question in the title, are thereby deduced. The requisite neuronal systems needed to provide animal experience, and the problem of assessing the quality and quantity of such experience, will then be considered. In conclusion, animal consciousness is seen to exist broadly across those species with the requisite control structures; the level of pain and other sensations depends in an increasingly well-defined manner on the complexity of the cerebral apparatus.

Defining perception, awareness, consciousness and reflexive or self-reflexive consciousness is difficult. I will not linger on definitions of fuzzy concepts but will attempt to put forward evidence for the rationale that awareness is likely to emerge as a consequence of how the brain processes information. Efficiency in information processing has resulted in a limited number of preferential (motivational) states of the brain and, in fact, of the whole organism. In addition, animals have the ability to internally represent external conditions and, through interactions with the motivational state, generate expectations.

It is argued that optimal decision-making requires that possible sequences of behaviours each activate their associated neuronal networks representing cue- and context-related information. Prior to the initiation of an action, the consequences of each possible scenario are estimated. An efficient animal must have the ability to anticipate, weight and choose. This weighting occurs at a hierarchically higher level and results in signals which possess a coordinative function in activating the appropriate motivational state, response selection, activation of associated networks and maintenance of attention.

Higher cognitive executive centres perceive and recognize such signals and integrate ongoing behaviour with internal representations about the past and expectations within the context of the signal induced state. Humans experience these simultaneously-occurring processes as awareness. The nature of the subjective experience may vary from an emotional state to reflexive consciousness depending on the cognitive abilities of the species and the stage of development and the level of arousal in the individual.

Determining objective measures for proof of consciousness in non-human animals has been helped by improved understanding of neural correlates of human consciousness. Functional imaging and neuropsychological studies have shown remarkable overlap between structures involved in actual perception of social and non-social objects and those involved in forming mental images of them. One area of particular interest is individual face recognition. This involves regions of the temporal lobe that are mainly only activated by actual perception or mental imagery of faces. Using behavioural, neuroanatomical and neurophysiological approaches in sheep, we have found that they have similar specialized abilities for recognizing many individuals from their faces. They have developed the same specialized neural processing regions in the temporal lobe for aiding such recognition. Furthermore, parallel activation of other brain regions controlling behavioural and emotional responses only occurs when they are overtly interested in the individuals whose faces they perceive. Such interest might therefore equate to their becoming consciously aware of them. Preliminary experiments have indicated that sheep may form and use mental images and that the regions of the temporal lobe that respond to faces can also do so under conditions where faces are suggested but do not actually appear. Such similarities between humans and sheep in this form of social recognition make it difficult to claim that humans can form mental images of faces whereas sheep cannot. While the ability to form and use mental imagery is not in itself definitive proof of consciousness, it is an important component part.

It is a popular notion that, compared to vertebrates, invertebrates have a reduced capacity to experience suffering. This is usually based on arguments that invertebrates show only simple forms of learning, have little memory capacity, do not show behavioural responses to stimuli that would cause ‘higher’ vertebrates to exhibit responses indicative of pain, and have differences in their physiology that would preclude the capacity for suffering. But, how convincing is this ‘evidence’ of a reduced capacity to suffer? Suffering is a negative mental state - a private experience - and, as such, it cannot be measured directly. When assessing the capacity of an animal to experience suffering, we often compare the similarity of its responses with those of ‘higher’ animals, conceptualized in the principle of argument-by-analogy. By closely examining the responses of invertebrates, it can be seen that they often behave in a strikingly analogous manner to vertebrates. In this paper, I discuss published studies that show that invertebrates such as cockroaches, flies and slugs have short- and long-term memory; have age effects on memory; have complex spatial, associative and social learning; perform appropriately in preference tests and consumer demand studies; exhibit behavioural and physiological responses indicative of pain; and, apparently, experience learned helplessness. The similarity of these responses to those of vertebrates may indicate a level of consciousness or suffering that is not normally attributed to invertebrates. This indicates that we should either be more cautious when using argument-by-analogy, or remain open-minded to the possibility that invertebrates are capable of suffering in a similar way to vertebrates.

‘Mindreading’ or theory of mind (ToM) refers to the capacity to attribute mental states to others. This ability is regarded as a critical component of what has, to date, exclusively characterized the advanced social cognition displayed by humans. The false belief task is a key test for ToM in different animal species. On a standard non-verbal false belief task, humans pass from age 4, whereas non-human primates consistently fail. Neuroanatomical and behavioural evidence for dolphins, however, indicates that they are capable of passing ToM tasks. The current paper represents a synthesis of the relevant dolphin research on neocortical evolution and non-invasive behavioural tests of precursors for ToM and the attribution of beliefs. The success of dolphins on attribution of belief tasks, in the absence of learning or cueing, indicates that they are capable of ‘mindreading’. What are the implications of animal ‘mindreading’? ToM tasks probe for reflexive consciousness and, by this criterion, dolphins may display reflexive consciousness. The implication of this conclusion is that future behavioural studies of social cognition will have considerable ethical and legal implications for animal welfare.

This paper reviews the debate that is currently taking place in the field of philosophy of mind on different conceptual models of consciousness. More and more philosophers argue that the explanation of subjective phenomena requires two complementary perspectives of understanding, known as the first- and third-person perspectives. The third-person perspective (ie conventional objectivity) accounts for the physical, functional aspects of consciousness, while the first-person perspective addresses the subjective, experiential aspects of consciousness. It is suggested that each of these conceptual perspectives may facilitate a different type of research in the study of animal emotion. Within the conventional, third-person perspective, a growing enthusiasm for issues of animal consciousness has led to sophisticated physical and cognitive models of animal emotion. The potential of the firstperson perspective, however, to provide a basis for models of animal subjective experience has remained largely unexplored. The paper concludes with a brief review of the author's recent experimental work on concepts of animal behavioural expression. The high reliability and repeatability of such concepts indicates that the first-person perspective may provide a valid research perspective in its own right.

Retrieved memories of emotionally laden events are likely to influence the ongoing emotional state and behaviour of animals. If animals consciously experience memories and/or associated emotions, then recall of aversive or pleasurable events will affect their welfare. Even if they do not, retrieval of these (non-conscious/implicit) memories may result in behaviour, such as attempts to escape, that could lead to injury and damage. There is growing evidence that emotionally laden events are more readily stored in memory than neutral ones, and that the neurophysiological basis of this, involving acute elevations of the classic stress hormones and the action of the amygdala, is similar in humans and other vertebrate species. Thus, in humans and animals, emotional memories are likely to be stored as priority information and may readily be retrieved in the presence of relevant cues. If so, an important practical goal is to minimize the chances of negative emotional memories being cued inappropriately, especially for animals in captivity. Disruption of memory formation and retrieval is also important in an animal welfare context. Chronic or very high elevations of stress hormones appear to have both short- and long-term effects on brain structure and function that can interfere with efficient storage of information. Environmental disturbances, including common husbandry procedures, can also disrupt memory formation through retroactive interference effects. Elevated stress levels may both increase the chances of retrieval of negative information while hampering the retrieval of positive or neutral information. These effects may lead to poor learning abilities, selective or disrupted memory retrieval, and consequent inappropriate behaviour with adverse welfare consequences. If we understand them, we may be able to recommend housing or husbandry procedures that minimize the likelihood of their occurrence.

Awareness of the self and awareness of others are difficult faculties to define. Part of the problem lies in the wide range of abilities that involve various aspects of awareness. Some of the most commonly studied abilities focus on the self-awareness of the individual. These abilities range from the capacity to distinguish self from non-self to the competency to reflect on one's past, present or future condition. Another set of abilities that is relevant to the study of awareness involves the interactions of individuals, and includes behaviours such as deception and empathy. We explore the possibility that species other than humans engage in deception and empathy, and consider the implications of such behaviours for self-awareness and other-awareness in these species. Although examples from a variety of species are provided, many examples come from dolphins and whales. This reflects both the authors’ interest in these animals and the possibility that large-brained creatures are more likely to engage in deliberate deception and/or true empathy.

Whereas physiological and behavioural responses to acute stressors are well documented, chronic stress remains difficult to assess in farm animals. The aim of the present paper is to investigate whether calves’ behavioural reactions to acute events are modified during chronic intermittent stress. Thirty-two calves housed in pairs were used. For half of the calves the partner and the pen were changed once a week for 14 weeks (regrouped calves) while the others remained unchanged (controls). Four behavioural tests were performed to assess calves’ reactivity to novel or sudden events, to predator cues and to restraint. In the water spray test, regrouped calves were startled more often. In the umbrella test, regrouped calves took a longer time to feed in front of the closed umbrella but no differences between the two treatments were observed on opening the umbrella. In the dog test, regrouped calves moved more and looked at the dog more often. In the restraint test, regrouped calves were more agitated. These differences disappeared when the tests were repeated. In conclusion, repeated changes in the social and physical environment of calves enhances their behavioural reactivity to novelty. This is likely to make them more adaptive to potential changes in their environment.

In humans, psychological manipulations such as hypnosis, behavioural modifications, relaxation training and cognitive behaviour therapy have all been used to reduce pain intensity. One thing these treatments have in common is selective attention. Work on attention-based cognitive coping strategies has shown that they have potentially useful analgesic qualities in pain therapy. In animals, there have been few studies on the effects of attentional shifts on pain perception. There is extensive literature on stress-induced analgesia and it is likely that, in some of the experiments, attention could be an important variable. This paper will present some of our recent work on selective attention and pain perception using the sodium urate model of gouty arthritis. Birds are naturally prone to articular gout and the model we have developed mimics acute gouty attacks in a single joint. Experimental sodium urate arthritis produces a tonically painful inflammation lasting for at least 3h during which time the animals show pain-related behaviours. Changes in motivation can reduce these pain-related behaviours and it has been hypothesized that these motivational changes act by way of altering the attention of the animal away from pain. The motivational changes investigated included nesting, feeding, exploration and social interactions. The degree of pain suppression ranged from marked hypoalgesia to complete analgesia and as such demonstrates a remarkable ability to suppress tonic pain. These shifts in attention not only reduced pain but also significantly reduced peripheral inflammation. These results are discussed in terms of the limited capacity models of attention.

It is widely agreed that all animals are entitled to some degree of welfare consideration, but that some are entitled to more consideration than others. However, the basis for singling out some animals for special consideration often seems to be mostly a matter of degree of similarity to, or association with, humans. A more reasonable criterion would involve the extent of suffering caused by given events. Two variables that seem likely to be very important in the extent of suffering are the capacity to anticipate and the capacity to recall. Everyday experience tells us that human suffering can be hugely amplified by either anticipation or recall of painful or distressing events. In the past, psychologists have tended to take the view that both these processes depend on the possession of language, and were therefore irrelevant to species other than humans. But comparative psychologists are increasingly making use of concepts from human cognition, including both memory and anticipation, to explain animals’ responses to both past and future events. These processes are invoked to explain the behaviour of a wide range of vertebrate species. Recent work on primate cognition indicates that more elaborate forms of representation may be possible in the great apes. Such evidence should be used as the basis for deciding whether to give special welfare consideration to certain species which have special cognitive capacities — or indeed enhanced welfare consideration to a wider range of species, if their cognitive capacities are found to be more sophisticated than is generally assumed.

The stressful effects that environments have on farm and laboratory animal welfare are likely to depend on how much animals understand of the behaviour and intentions of their conspecifics as well as on their understanding of their physical environment. However, studies on animal social cognition have primarily focused on primates. Here, we report on our work on social cognition in domestic pigs. It focuses on the ability of domestic pigs to assess and use to their advantage the behaviour of conspecifics, and uses approaches pioneered in studies on primates. Our work has shown that dominant pigs use the privileged knowledge of a subordinate to their own advantage in a competitive foraging situation. While such exploitative behaviour is likely to be based on rapid learning about the subordinate ‘s behaviour, it is also possible that ‘higher’ cognitive abilities such as visual perspective taking could be involved. Ongoing work uses an adaptation of the Guesser-Knower paradigm to test whether pigs are indeed capable of visual perspective taking.

We investigated the ability of hooded crows to form transitive inferences. Subjects were trained to discriminate a series of overlapping pairs of stimuli: A+ B-, B+ C-, C+ D-, D+ E, where the letters stood for colour stimuli and plus and minus for rewarded or non-rewarded choices. The stimuli were cards of different colours with a circle of the same colour on the reverse side and diameters decreased from A to E. To preclude an influence of the reinforcement history on choices with the test pair BD, an overcompensation phase was instituted after training. It consisted of the presentation of all training pairs with frequencies selected so that the reward to non-reward ratios for stimulus D would be between 1.5 and 2.0 times greater than for B. If, during the BD test, the bird chose the stimuli according to these ratios they should prefer D. If they chose according to diameter relation they should prefer B. During these tests, the crows strongly preferred B over D (83.1%). In a second experiment, subjects were trained with the same procedure except that the diameters of the circles were all the same. During this test, the performance of two crows was not significantly different from chance level (53.1%), and the other two crows preferred D (80.0%). We conclude that crows can solve transitivity tests using cognitive mechanisms if they are offered additional information (in this case circle diameter) which, presumably, allows them to represent the relevant stimuli in an ordered series.