The assumption that animals are conscious and capable of experiencing negative sensations and emotions is at the core of most people's concerns about animal welfare. Investigation of this central assumption should be one goal of animal welfare science. We argue that theory and techniques from cognitive science offer promising ways forward. Evidence for the existence of conscious and non-conscious cognitive processing in humans has inspired scientists to search for comparable processes in animals. In studies of metacognition and blindsight, some species show behaviour that has functional parallels with human conscious cognitive processing. Although unable to definitively answer the question of whether the animals are conscious, these studies provide fresh insights, and some could be adapted for domestic animals. They mark a departure from the search for cognitive complexity as an indicator of consciousness, which is based on questionable assumptions linking the two. Accurate assessment of animal emotion is crucial in animal welfare research, and cognitive science offers novel approaches that address some limitations of current measures. Knowledge of the relationship between cognition and emotion in humans generates a priori frameworks for interpreting traditional physiological and behavioural indicators of animal emotion, and provides new measures (eg cognitive bias) that gauge positive as well as negative emotions. Conditioning paradigms can be used to enable animals to indicate their emotional state through operant responses. Although evidence for animal consciousness and emotion will necessarily be indirect, insights from cognitive science promise further advances in our understanding of this fundamentally important area in animal welfare science.

Farming and laboratory industries face questions about whether to breed animals with altered capacities for pleasure and pain. This paper addresses this issue from different approaches to animal welfare based on experiences, fitness and naturalness. This can illuminate both the breeding-related issues and the different approaches themselves. These differences have practical implications for decisions about animal breeding. All three approaches will agree that pleasure that is adaptive in natural environments has positive value and that maladaptive pain has negative value. However, where animals’ environments will not be natural, experiences-based approaches may support breeding animals that experience more pleasure and less pain or insentient animals; whereas, in some cases, fitness-based and naturalness-based approaches might favour the breeding of animals that experience more pain and less pleasure.

The welfare of horses involved in sport and leisure activities has come under increasing scrutiny, both from within the equine sector and from the public. A systematic review of scientific evidence was conducted to derive observable, evidence-based behavioural measures of positive or negative affective state and factors relating to quality of life in the domestic horse (Equus caballus). Two separate searches (including the terms ‘emotion/affect’, or ‘stress’) were conducted, with 179 articles being retained. In Part I of this two-part review (companion paper published simultaneously), articles relating to the extent to which the species-specific needs of the horse are fulfilled in the home environment (n = 21), in relation to social grouping (n = 20), and during weaning (n = 14) were reviewed. Experimental tests of affective state in relation to housing and management (n = 8), and studies relating to stereotypical behaviour (n = 7) were also included. Opportunities for behavioural expression were dependent upon the provision of social and physical resources. Withdrawn or agitated behaviours in situ, avoidance behaviour during handling and agonistic intra-species interactions were indicative of negative affective state. Affiliative intra-specific social interactions, and forage ingestion were considered positive signs. For horses to live a good life, their need for space, companionship, and forage must be prioritised from birth and throughout their lives.

Quality of life is dependent upon the extent to which behavioural needs are met, and the balance between pleasant and unpleasant lifetime experiences. In Part II of this systematic review, articles (n = 109) relating to horse-human interactions were reviewed to identify behavioural evidence of their positive or negative impact on the horse. The number of articles (n = 22) relating to the recognition of pain in horses, indicated the importance of identifying health issues, which are also likely to increase the aversiveness of interactions. These and articles relating to emotional reactivity testing in horses (n = 19), the behaviour of horses during handling and management procedures (n = 17), behaviour of the horse when ridden (n = 17), non-procedural horse-human interactions (n = 13), horse behaviour during transportation (n = 12) and behaviour during training other than when ridden (n = 9) were reviewed. During most interactions, horse behaviour is controlled and/or restricted by the human, masking negative or positive signs, and may be confounded by factors including fear and individual differences. In situations involving freedom of movement, positive experiences of horses with humans were associated with approach behaviour, negative ones with avoidance, but training could affect both. Undoubtedly, change is needed to reduce the extent to which interactions with humans are unpleasant for the horse. Only when the needs of the horse are fulfilled and interactions with humans are predominantly pleasurable will their quality of life improve.

Emotions are now largely recognised as a core element in animal welfare issues. However, convenient indicators to reliably infer emotions are still needed. As such, the availability of behavioural postures analogous to facial expressions in humans would be extremely valuable for animal studies of emotions. The purpose of this paper is to find out stable expressive postures in sheep and to relate these expressive postures with specific emotional contexts. In an initial experiment, we identified discrete ear postures from a comprehensive approach which integrates all theoretically distinguishable ear postures. Four main ear postures were identified: horizontal ears (P posture); ears risen up (R posture); ears pointed backward (B posture); and asymmetric posture (A posture). In a second experiment, we studied how these ear postures were affected by specific emotional states elicited by exposing sheep to experimental situations in which elementary characteristics (ie suddenness and unfamiliarity, negative contrast and controllability) were manipulated. We found that: i) the horizontal P posture corresponds to a neutral state; ii) sheep point their ears backward (B posture) when they face unfamiliar and unpleasant uncontrollable situations, hence likely to elicit fear; iii) they point their ears up (R posture) when facing similar negative situations but controllable, hence likely to elicit anger; and iv) they expressed the asymmetric A posture in very sudden situations, likely to elicit surprise. By cross-fostering psychological and ethological approaches, we are able to propose an interpretation of ear postures in sheep relative to their emotions.

With recent increased focus on positive welfare in animal welfare science, there is demand for objective positive welfare indicators. It is unclear whether changes in body surface temperature can be used to non-invasively identify and quantify positive states in mammals. We recorded continuous measurements of tail surface temperature using infra-red thermography (IRT) and concurrent behavioural observations in male and female Wistar rats (Rattus norvegicus). If tail surface temperature can differentiate between positive and negative experiences, we expect a qualitatively different response compared to negative experiences. Three groups of rats were presented with increasing magnitudes of food rewards (neutral/none, one and three rewards). The rats were placed in an arena to which they were habituated and filmed for 30 s before and 30 min after exposure to different rewards. Tail temperature initially decreased from the pre-reward baseline and subsequently returned towards baseline temperature. The overall pattern of the change was the same as for rats subjected to negative stimuli in previous studies. Nevertheless, dynamic changes in tail temperature, specifically the rate of recovery and the behavioural response (exploration), differed between neutral and rewarded rats but failed to distinguish reward magnitude. Sex differences were found in both thermal and behavioural responses, unrelated to reward magnitudes. Female rats exhibited a greater initial response with a slower recovery than male rats, emphasising the value of using of both sexes in animal welfare research. This study improves our understanding of the effects of positive emotions induced by food reward on peripheral body temperature and behaviour.

There is an increasing requirement for tools to assess and improve animal welfare in an objective and scientifically based manner. In our research a concept of welfare is applied which states that welfare is determined by the balance between positive and negative experiences. This concept implies that an interaction exists between stress systems and reward systems in the brain and, as a consequence: (I) negative experiences induce an increased sensitivity (ie need) for positive experiences; and (II) negative experiences can be compensated for by positive experiences. On this basis, two uses of reward-related behaviour can be hypothesised: (I) reward sensitivity may be used as a tool to assess the state of an animal in terms of welfare because it can indicate the current state of the balance that is dependent on previous (stressful) experiences; and (II) regular presentation of rewards may serve as a tool to counteract stress by shifting the balance to the positive side and, thus, to improve welfare. In order to investigate this, we used the rat as a model. Reward sensitivity was determined by the spontaneous behavioural response shown during expectation of a reward (ie anticipatory behaviour). A third (III) use of reward-related behaviour derives from the fact that anticipatory behaviour is influenced by the (rewarding) properties of the forthcoming reward (or other event) and, thus, may serve as a tool to assess the animal's perception of this reward/event. This paper presents a descriptive overview of the evidence obtained thus far for the three proposed uses of reward-related behaviour. The biological background of our concept of welfare can be generalised to all (vertebrate) species, and anticipatory behaviour can be evoked in a wide range of other species. Therefore, this tool for measuring and improving the welfare of captive animals has great potential and will contribute to a good quality of life for captive animals.

A number of studies have investigated anticipatory behaviour in animals as a measure of sensitivity to reward or as an expression of emotional state. A common feature of many studies is that they base inferences on seemingly arbitrary measures, for example, the frequency of behavioural transitions (ie number of times an animal switches between different behaviours). This paper critically reviews the literature and discusses various hypotheses for why specific behavioural responses occur in the anticipatory period between the signal and reward in conditioned animals. We argue that the specific behaviours shown may be the result of superstitious learning and thus highly variable, leaving behavioural transitions as the only response that can be scored consistently, and that sometimes these responses may relate more to frustration than to a positive emotional state. Finally, we propose new research approaches to avoid potential confounds and improve future studies on this topic.

Contemporary animal welfare thinking is increasingly emphasising the promotion of positive states. There is a need for existing assessment frameworks to accommodate this shift in emphasis. This paper describes extensions to the Five Domains model, originally devised to assess welfare compromise, that facilitate consideration of positive experiences that may enhance welfare. As originally configured, the model provided a systematic method for identifying compromise in four physical/functional domains (nutrition, environment, health, behaviour) and in one mental domain that reflects the animal's overall welfare state understood in terms of its affective experiences. The specific modifications described here now facilitate additional identification in each domain of experiences animals have which may be accompanied by positive affects that would enhance welfare. It is explained why the grading scale and indices for evaluating welfare compromise necessarily differ from those for assessing welfare enhancement. Also, it is shown that the compromise and enhancement grades can be combined to provide a single informative symbol, the scaled use of which covers the range from severe welfare compromise and no enhancement to no compromise and high-level enhancement. Adapted thus, the Five Domains model facilitates systematic and structured assessment of positive as well as negative welfare-related affects, the circumstances that give rise to them and potential interactions between both types of affect, all of which extend the utility of the model. Moreover, clarification of the extended conceptual framework of the model itself contributes to the growing contextual shift in animal welfare science towards the promotion of positive states whilst continuing to minimise negative states.

Promotion of positive experiences in companion animals is essential for maximising good welfare. However, the dearth of published literature on the experience and expression of positive emotional states in companion dogs suggests they are less well understood than negative emotions. Owner knowledge can provide a basis for generating hypotheses for experimental research, and can inform education initiatives. An online survey of 445 dog (Canis familiaris) owners in the United Kingdom and the Republic of Ireland was used to identify key contexts and behaviours perceived by owners to be associated with positive emotions for companion dogs, and to examine factors which influence owner reports of key behaviours. The contexts most commonly associated with positive high arousal (PHA; ‘happy and excited’) were anticipation of walks or food and with positive low arousal (PLA; ‘happy and relaxed’) were resting and gentle stroking. Respondents’ behavioural profile for canine PHA involved barking, head held high, wide open and ‘bright’ eyes, ears pricked, tail wagging, mouth open, and active, playful behaviour. For PLA, respondents collectively described their dogs as silent, head resting, eyes closed or slightly closed, ears ‘down’, mouth closed and a calm/relaxed activity level. Notably, PLA states were described in less detail than PHA, suggesting the former may be less well understood or difficult to interpret. Dog breed and age, and owner experience and level of attachment to their pet significantly influenced respondents’ likelihood to report certain behavioural indicators, and may influence assessments of pet behaviour and underlying emotion. Further work is required to determine the validity of the behavioural expression and contexts perceived to be associated with positive experiences in dogs.

In hedonic theories of motivation, ‘motivational affective states’ (MASs) are typically seen as adaptations which motivate certain types of behaviour, especially in situations where a flexible or learned response is more adaptive than a rigid or reflexive one. MASs can be negative (eg unpleasant feelings of hunger or pain) or positive (eg pleasant feelings associated with eating and playing). Hedonic theories often portray negative and positive MASs as opposite ends of a one-dimensional scale.

We suggest that natural selection has favoured negative and positive affect as separate processes to solve two different types of motivational problems. We propose that negative MASs (eg thirst, fear) evolved in response to ‘need situations’ where the fitness benefit of an action has increased, often because the action is needed to cope with a threat to survival or reproductive success. We propose that these negative MASs develop in response to a change in the body (eg dehydration) or the environment (eg the approach of a predator) which creates the need for action, and that negative MASs can become intense and prolonged if the threat to fitness is high and persistent. We propose that positive MASs evolved in ‘opportunity situations ‘ where an action (eg playing, exploring) has become advantageous because the fitness cost of performing it has declined. We propose that these positive MASs occur during, or as a result of, the performance of types of behaviour which are beneficial for fitness at a variety of times, not only when they are required to meet immediate needs; and that the pleasure inherent in the behaviour motivates the animal to perform it when the cost of so doing is sufficiently low. Some behaviour (eg eating) can be motivated by both positive and negative affect. Other behaviour, such as playing or fleeing from a predator, may be motivated largely by positive or negative affect alone. Our hypothesis needs to be tested, but we suggest that it corresponds well to common human experience.

The hypothesis provides a basis for predicting whether an aspect of animal management is likely to cause strong and prolonged negative affect (‘suffering’), or to prevent animals from experiencing certain types of pleasure. This distinction is important for bringing animal welfare assessment into line with ethical concerns.

An animal's welfare state is intrinsically linked to its affective state. Evidence suggests that sentient, conscious animals can experience a range of affective states, such as pain, fear or boredom as well as positive affects like joy, curiosity, satiation or lust. In the behavioural assessment of animal welfare, there is increasing recognition that it is not simply which behaviours an animal engages in but also the quality of its movement. Kinematics is an approach which is being more widely applied to the behavioural assessment of animal welfare. Kinematics is a field of mechanics that describes the movement of points on a body by defining these points in a coordinate system and precisely tracking how they change in terms of space and time. A major opportunity exists for using kinematic technology to inform our understanding of the emotional state of animals. This review argues that kinematics is a useful methodology for identifying and characterising movement indicative of an animal's affective state. It demonstrates that kinematics: i) appears useful in detecting subtleties in the expression of affective states; ii) could be used in conjunction with, and add extra information to, affective tests (for example, an approach/avoidance paradigm); and iii) could potentially, eventually, be developed into an automated affective state detection system for improving the welfare of animals used in research or production. Furthering our knowledge of animal affective states using kinematics requires engagement from many areas of science outside of animal welfare, such as sports science, computer science, engineering and psychology.