Sensitivity to reward loss as an indicator of animal emotion and welfare

Effects of temporary access to environmental enrichment on measures of laboratory mouse welfare

Laboratory mice are typically housed in "shoebox" cages with limited opportunities to engage in natural behaviour. Temporary access to environments with increased space and complexity (playpens) may improve mouse welfare. Previous work by our group has shown that mice are motivated to access and use these environments, but it is unknown how other aspects of welfare are impacted. Female C57BL/6J, BALB/cJ, and DBA/2J mice (n = 21; 7 mice per strain) were housed in mixed-strain trios and given temporary access to a large playpen with their cage mates three times per week. Control mice (n = 21; 7 mice per strain) remained in their home cages. Home cage behaviour (development of stereotypic behaviour over time, aggression following cage-changing) and anxiety tests were used to assess how playpen access impacted welfare. Contrary to our predictions, we found increased time spent performing stereotypies in playpen mice; this difference may be related to negative emotional states, increased motivation to escape the home cage, or active coping strategies. Playpen access resulted in strain-dependent improvements in aggression and some measures of anxiety. Aggression was lower for C57BL/6J mice in the playpen treatment following cage changing than it was for C57BL/6J control mice, while playpen mice, and particularly the C57BL/6J strain, spent more time in the center of the open field test and produced fewer fecal boli during anxiety testing, supporting other research showing that strain differences play an important role in behaviour and stress resiliency.

What if the reward is not as yummy? Study of the effects of Successive Negative Contrast in domestic dogs in two different tasks

Successive Negative Contrast (SNC) occurs when there is a reduction in the quantity or quality of a reward that is expected according to the presence of contextual cues. This induces an emotional response of frustration that is similar to stress. While this phenomenon has been observed in several mammal species, findings in domestic dogs have been inconsistent, although this issue has strong relevance in dog training. The aim of this study was to assess the effects of Successive Negative Contrast in two responses that had already been studied in this species, but with an increase in the methodological rigor and variations in the experimental conditions to examine the generalizability of the phenomenon. To this end, experimental dogs experienced a pre-shift phase in which they received a high-value reward (liver), followed by a post-shift phase in which they obtained a low-value reward (dry dog food), and then a re-shift phase in which the high-value reward was available again. Control dogs received dry food in all phases. The results show a contrast effect on the behavior of following human pointing to obtain food (Study 1). On the contrary, there were no differences in problem solving behavior after the de- and re-evaluation of the reward during a non-social task (Study 2). The results support that Successive Negative Contrast is not a consistent phenomenon in pet dogs. It is possible that certain characteristics of dogs such as the great availability of high-value rewards in their daily lives could attenuate the effects of a reduction in incentive value.

Trait sensitivity to stress and cognitive bias processes in fish: A brief overview

Like other animals, fish have unique personalities that can affect their cognition and responses to environmental stressors. These individual personality differences are often referred to as "behavioural syndromes" or "stress coping styles" and can include personality traits such as boldness, shyness, aggression, exploration, locomotor activity, and sociability. For example, bolder or proactive fish may be more likely to take risks and present lower hypothalamo-pituitary-adrenal/interrenal axis reactivity as compared to shy or reactive individuals. Likewise, learning and memory differ between fish personalities. Reactive or shy individuals tend to have faster learning and better association recall with aversive stimuli, while proactive or bold individuals tend to learn more quickly when presented with appetitive incentives. However, the influence of personality on cognitive processes other than cognitive achievement in fish has been scarcely explored. Cognitive bias tests have been employed to investigate the interplay between emotion and cognition in both humans and animals. Fish present cognitive bias processes (CBP) in which fish's interpretation of stimuli could be influenced by its current emotional state and open to environmental modulation. However, no study in fish has explored whether CBP, like in other species, can be interpreted as long-lasting traits and whether other individual characteristics may explain its variation. We hold the perspective that CBP could serve as a vulnerability factor for the onset, persistence, and recurrence of stress-related disorders. Therefore, studying fish's CBP as a state or trait and its interactions with individual variations may be valuable in future efforts to enhance our understanding of anxiety and stress neurobiology in animal models and humans.

Social housing improves dairy calves' performance in a competition test

On most dairy farms, calves are housed individually until weaning. However, depriving calves of an early social environment impairs behavioral development. We studied the effect of early-life social housing on calves' competitive skills. In this study, Holstein heifers were pseudorandomly assigned to either individual housing (n = 9) or pair housing (with a nonfocal companion, n = 9) at the age of 11 d. After 14 d of housing treatment, calves underwent a competition test for milk access against a group-reared calf; consisting of 2 test sessions per day for 5 d (session duration: 74.42 ± 2.29 s; mean ± standard error). Pair-housed calves performed better than individually housed calves: throughout the competition days, individually housed calves increased their latency to approach the milk bottle and decreased their time spent drinking in contrast to pair-housed calves, which exhibited stable latencies to reach the milk bottle and increased their time drinking. To control for the influence of personality on their competitive abilities, all calves were subjected to personality tests assessing boldness before being exposed to the housing treatment. Our findings indicate that calves assessed as bolder during the pretreatment personality test tended to approach the milk bottle faster. Our results provide additional evidence of the beneficial effects of social housing on dairy calves' behavioral development.

Exploring the effect of pain on response to reward loss in calves

Negative emotional states are known to interact, potentially aggravating one another. In this study, we used a well validated paradigm (successive negative contrast, SNC) to determine if pain from a common procedure (disbudding) influences responses to a reward downshift. Holstein calves (n = 30) were trained to approach a 0.5 L milk reward. Latency to approach, number of vocalisations and pressure applied on the bottle were recorded during training. To assess how pain affected responses to reward downshift, calves were randomly assigned to one of three treatments before the downshift. Two groups were disbudded and provided the 'gold standard' of pain mitigation: intraoperative local anesthesia and analgesia. One of these disbudded groups was then provided supplemental analgesic before testing. The third group was sham disbudded. All calves were then subjected to the reward downshift by reducing the milk reward to just 0.1 L. Interactions were detected between test session and daily trials on pressure applied for the Disbudded group (estimate ± SEM: 0.08 ± 0.05), and on vocalisations for the Sham (0.3 ± 0.1) and Disbudding + Analgesia (0.4 ± 0.1) groups. Our results indicate that SNC is a promising paradigm for measuring negative affect in calves and suggests that pain potentially affects the response to a reward downshift.

Affective trajectories: Are hens influenced by positive and negative changes in their living conditions?

Most studies of the effects of housing and husbandry on animals' affective states and welfare investigate the impact of stable living conditions, comparing for example, animals living in enriched environments with those living in non-enriched ones. Changes in living conditions, including from more to less enriched environments, have also been found to have effects on measures of affective state and welfare in some species. But these studies have not investigated whether it is the trajectory of change that has affected the animals (e.g., worsening conditions), or simply the nature of their final environment (e.g., non-enriched). Here, we hypothesised that laying hens living in worsening conditions across a six-week period (gradually moving from preferred to non-preferred living conditions; "Trajectory to Non-Preferred", TNP, n = 30), would show evidence of more negative affective states and poorer welfare than those living continuously in non-preferred conditions for the same duration ("Stable Non-Preferred", SNP, n = 30). We also hypothesised that hens living in improving conditions (gradually moving from non-preferred to preferred living conditions; "Trajectory to Preferred", TP, n = 30), would show evidence of more positive affective states and better welfare than those living continuously in preferred conditions ("Stable Preferred", SP, n = 30). The preferred living condition provided extensive resources and intermittent rewarding events (such as the delivery of food treats) known to be valued and preferred by most hens, while the non-preferred living condition provided just basic resources and intermittent aversive events (e.g., loud noises). The hens' affective states and welfare were measured using home-pen behavioural observations, body condition assessments, physiological stress measures (e.g., blood corticosterone, glucose, etc.), physical challenge tests, and judgement bias tests. A number of differences between hens in the trajectory and stable living conditions were found: TP hens were lighter, showed more foraging behaviour and less standing alert and head-shaking than SP hens, while TNP hens showed more head-shaking, mild feather pecking and aggressive attacking of pen mates than SNP hens. However, some of these differences failed to reach significance following Benjamini adjustments for multiple testing. The groups also did not differ in their judgement biases (measured in a sub-sample of 12 hens per experimental group), response to physical challenges, or measures of physiological stress. We conclude that the hens in the present study showed some evidence of responsiveness to 'affective trajectories' in their living conditions, but no definitive effects on their affective states and welfare.

Investigating attentional scope as a novel indicator of emotional state in animals

In humans, contrasting emotional states can lead to a broadening or narrowing of attentional scope. Whether this is also the case in animals has yet to be investigated. If confirmed, measurement of attentional scope has potential as a novel cognitive method of welfare assessment. In this study, we therefore aimed to investigate a test of attentional scope as a measure of emotional state in animals. We did this by inducing four putatively different emotional states in dogs (N = 10), varying in valence (positive, negative) and arousal (high, low), in two different reward contexts (food rewards in Experiment 1, social rewards in Experiment 2) and then assessing dogs' behavioural responses in a test of attentional scope. We also recorded heart rate variability (HRV) parameters as additional confirmatory affective indicators. In Experiment 1, the dogs showed a narrowing of attentional scope after the induction of both positively valenced emotional states. That dogs were in a positive state was supported by the reduced Standard Deviation of normal-to-normal R-R intervals (SDNN) and the reduced Low Frequency (LF) and Very Low Frequency (VLF) HRV. In Experiment 2, when responses to social rewards were examined, we did not detect any statistically significant differences in attentional scope between the emotional states, but dogs had a slightly narrow attentional scope in the negatively valenced emotional states. The LF tended to be reduced in the high arousal positive treatment. In conclusion, our study provides the first indication that emotional states can also alter attentional scope in animals. The results justify further investigation of this approach for use in animal welfare assessment, although additional studies are needed to refine predictions.

Is an increase of glucocorticoid concentrations related to the degree of arousal or valence experienced by an animal to a stimulus?

Animal welfare is the quality of life as perceived by the animal itself. It is also the state of an animal in its attempt to cope with its environment. Animal welfare has high ethics and economic importance. Thus the need to develop parameters for assessing animal welfare. An acute increase in glucocorticoid (GC) concentration is necessary for adaptation to a stressful situation. Glucocorticoids also play a significant role in metabolic, cardiovascular, and immune systems. Glucocorticoid enhances effective learning through the hippocampus and other normal body functions. That is why we remember events (either positive or negative) associated with strong emotions. Long-term secretion of GCs has catabolic effects. Thus, affecting animal health. Measuring GC is one of the ways of assessing animal welfare. But, high GC concentration does not only indicate pain or suffering. We report that stress and emotion trigger similar physiological responses. So, measuring GC levels cannot differentiate between positive and negative states. We conclude that GC shows circadian rhythms and episodic spikes in some species. Values from a single sample point are not reliable to make conclusions about a condition. Training animals for blood collection may reduce stress. Thus not causing bias in the GC concentration measured.

New Horizons for Phenotyping Behavior in Rodents: The Example of Depressive-Like Behavior

The evolution of the field of behavioral neuroscience is significantly dependent on innovative disruption triggered by our ability to model and phenotype animal models of neuropsychiatric disorders. The ability to adequately elicit and measure behavioral parameters are the fundaments on which the behavioral neuroscience community establishes the pathophysiological mechanisms of neuropsychiatric disorders as well as contributes to the development of treatment strategies for those conditions. Herein, we review how mood disorders, in particular depression, are currently modeled in rodents, focusing on the limitations of these models and particularly on the analyses of the data obtained with different behavioral tests. Finally, we propose the use of new paradigms to study behavior using multidimensional strategies that better encompasses the complexity of psychiatric conditions, namely depression; these paradigms provide holistic phenotyping that is applicable to other conditions, thus promoting the emergence of novel findings that will leverage this field.

Anticipatory behaviour as an indicator of the welfare of dairy calves in different housing environments

Anticipatory behaviour occurs in the period before a reward or other positive event is presented and has been interpreted as an indicator of the welfare and emotional state of animals. The use of this indicator has received limited attention in dairy calves. Therefore, we investigated how anticipatory behaviour is affected by housing environment and reward quality, and if anticipatory behaviour changes when reward quality changes unexpectedly. Sixteen pairs of calves were assigned to treatments in a 2 x 2 factorial design (two housing environment and two reward quality combinations). Housing was either basic (2 m2/calf, river stone surface) or enriched (5 m2/calf, woodchip, and enrichment items), and the reward was access to either an additional basic or enriched pen. Calves were conditioned to anticipate reward pen access; anticipatory behaviour toward receiving the reward pen was measured. Signaling reward access increased the frequency of transitions between behaviours and duration of touching and looking at the signal and exit door. Basic-housed calves showed more anticipatory behaviour (increased frequency of transitions between behaviours) and decreased latency to access the reward compared to enriched-housed calves, but the reward pen quality had no effect on anticipatory behaviour. When the reward pen quality changed from enriched to basic unexpectedly, resulting in sudden reward loss, basic-housed calves decreased, while enriched-housed calves increased, anticipatory behaviour. However, there was no change in anticipatory behaviour during reward gain (change from basic to enriched reward pen). Our findings align with previous work showing that animals in basic housing show more anticipation for a reward, and demonstrate suppressed behavioural response when experiencing reward loss, suggesting greater sensitivity to reward. Sensitivity to reward has associations with mood state; thus, calves in basic environments may experience a more negative emotional state, and thus reduced welfare, compared to calves in enriched environments.

Regular touchscreen training affects faecal corticosterone metabolites and anxiety-like behaviour in mice

Automated touchscreen techniques find increasing application for the assessment of cognitive function in rodents. However, hardly anything is known about the potential impact of touchscreen-based training and testing procedures on the animals under investigation. Addressing this question appears particularly important in light of the long and intensive training phases required for most of the operant tasks. Against this background, we here investigated the influence of regular touchscreen training on hormones and behaviour of mice. Faecal corticosterone metabolites (FCMs), reflecting corticosterone levels around the time of treatment, were significantly increased in touchscreen-trained mice, even one week after the training phase was already terminated. Such an effect was not detected on baseline FCMs. Thus, regular touchscreen training can be assumed to cause long-term effects on hypothalamus-pituitary-adrenal axis activity. Furthermore, anxiety-like behaviour was increased in touchscreen-trained mice two weeks after the end of the training phase. Traditionally, this would be interpreted as a negative influence of the training procedure on the animals' affective state. Yet, we also provide two alternative explanations, taking the possibility into account that touchscreen training might have enriching properties.

Negative mood affects the expression of negative but not positive emotions in mice

Whether and to what extent animals experience emotions is crucial for understanding their decisions and behaviour, and underpins a range of scientific fields, including animal behaviour, neuroscience, evolutionary biology and animal welfare science. However, research has predominantly focused on alleviating negative emotions in animals, with the expression of positive emotions left largely unexplored. Therefore, little is known about positive emotions in animals and how their expression is mediated. We used tail handling to induce a negative mood in laboratory mice and found that while being more anxious and depressed increased their expression of a discrete negative emotion (disappointment), meaning that they were less resilient to negative events, their capacity to express a discrete positive emotion (elation) was unaffected relative to control mice. Therefore, we show not only that mice have discrete positive emotions, but that they do so regardless of their current mood state. Our findings are the first to suggest that the expression of discrete positive and negative emotions in animals is not equally affected by long-term mood state. Our results also demonstrate that repeated negative events can have a cumulative effect to reduce resilience in laboratory animals, which has significant implications for animal welfare.

Reward and punisher experience alter rodent decision-making in a judgement bias task

The influence of affective states on decision-making is likely to be complex. Negative states resulting from experience of punishing events have been hypothesised to generate enhanced expectations of future punishment and ‘pessimistic’/risk-averse decisions. However, they may also influence how decision-outcomes are valued. Such influences may further depend on whether decisions at hand are germane to the rewards or punishers that induced the affective state in the first place. Here we attempt to dissect these influences by presenting either many or few rewards or punishers of different types (sucrose vs air-puff; 50 kHz vs 22 kHz ultrasonic vocalisations) to rats, and investigating their subsequent decisions in a judgement bias task that employed sucrose and air-puff as decision outcomes. Rats that received many sucrose pellets prior to testing were more risk-averse than those receiving many air-puffs. Ultrasonic vocalisations did not alter decision-making. Computational analysis revealed a higher weighting of punishers relative to rewards (in agreement with findings from a separate behavioural task) and a bias towards the risk-averse response following pre-test sucrose compared to pre-test air-puff. Thus, in this study reward and punisher manipulation of affective state appeared to alter decision-making by influencing both expectation and valuation of decision-outcomes in a domain-specific way.

Assessing cognitive control and the reward system in overweight young adults using sensitivity to incentives and white matter integrity

Cognitive control and incentive sensitivity are related to overeating and obesity. Optimal white matter integrity is relevant for an efficient interaction among reward-related brain regions. However, its relationship with sensitivity to incentives remains controversial. The aim of this study was to assess the incentive sensitivity and its relationship to white matter integrity in normal-weight and overweight groups. Seventy-six young adults participated in this study: 31 were normal-weight (body mass index [BMI] 18.5 to < 25.0 kg/m², 14 females) and 45 were overweight (BMI ≥ 25.0 kg/m², 22 females). Incentive sensitivity was assessed using an antisaccade task that evaluates the effect of incentives (neutral, reward, and loss avoidance) on cognitive control performance. Diffusion tensor imaging studies were performed to assess white matter integrity. The relationship between white matter microstructure and incentive sensitivity was investigated through tract-based spatial statistics. Behavioral antisaccade results showed that normal-weight participants presented higher accuracy (78.0 vs. 66.7%, p = 0.01) for loss avoidance incentive compared to overweight participants. Diffusion tensor imaging analysis revealed a positive relationship between fractional anisotropy and loss avoidance accuracy in the normal-weight group (p < 0.05). No relationship reached significance in the overweight group. These results support the hypothesis that white matter integrity is relevant for performance in an incentivized antisaccade task.

Challenges in the comparative study of empathy and related phenomena in animals

The aim of this review is to discuss recent arguments and findings in the comparative study of empathy. Based on a multidisciplinary approach including psychology and ethology, we review the non-human animal literature concerning theoretical frameworks, methodology, and research outcomes. One specific objective is to highlight discrepancies between theory and empirical findings, and to discuss ambiguities present in current data and their interpretation. In particular, we focus on emotional contagion and its experimental investigation, and on consolation and targeted helping as measures for sympathy. Additionally, we address the feasibility of comparing across species with behavioural data alone. One main conclusion of our review is that animal research on empathy still faces the challenge of closing the gap between theoretical concepts and empirical evidence. To advance our knowledge, we propose to focus more on the emotional basis of empathy, rather than on possibly ambiguous behavioural indicators, and we provide suggestions to overcome the limitations of previous research .

Insensitivity to reward shifts in zebrafish (Danio rerio) and implications for assessing affective states

Theory and empirical findings predict that individuals in a negative affective state are more sensitive to unexpected reward loss and less sensitive to unexpected reward gain compared to individuals in a neutral or positive affective state. We explore the use of sensitivity to reward shifts measured during successive contrast tasks as an indicator of affect in zebrafish (Danio rerio). In line with the assumption that exposure to rewarding stimuli induces a relatively positive affective state compared to exposure to stimuli that they do not prefer, we confirmed that zebrafish prefer enriched over barren environments, suggesting that the enriched environment is associated with positive affective states. We trained individuals to swim down a channel for food rewards of differing value and then presented them with unexpected increases or decreases in reward value. Contrary to our hypothesis, individuals conditioned to a high-value reward continued swimming at the same speed when reward value was downshifted, thus showing no successive negative contrast effect and appearing insensitive to reward loss. Individuals whose rewards were upshifted gradually increased their speed, but did not display successive positive contrast effects typical of sensitivity to reward gains. In both cases, housing type did not result in differences in swim time. One potential explanation is that goal-directed control of behaviour is necessary for an animal to show a successive contrast response to unexpected reward gain or loss, and the behaviour of zebrafish in this task was under habitual control, perhaps due to over-training. If so, refinements to task design and training procedures will allow further progress with this assay.

Effects of early life and current housing on sensitivity to reward loss in a successive negative contrast test in pigs

Animals in a negative affective state seem to be more sensitive to reward loss, i.e. an unexpected decrease in reward size. The aim of this study was to investigate whether early-life and current enriched vs. barren housing conditions affect the sensitivity to reward loss in pigs using a successive negative contrast test. Pigs (n = 64 from 32 pens) were housed in barren or enriched conditions from birth onwards, and at 7 weeks of age experienced either a switch in housing conditions (from barren to enriched or vice versa) or not. Allotting pigs to the different treatments was balanced for coping style (proactive vs. reactive). One pig per pen was trained to run for a large reward and one for a small reward. Reward loss was introduced for pigs receiving the large reward after 11 days (reward downshift), i.e. from then onwards, they received the small reward. Pigs housed in barren conditions throughout life generally had a lower probability and higher latency to get the reward than other pigs. Proactive pigs ran overall slower than reactive pigs. After the reward downshift, all pigs ran slower. Nevertheless, reward downshift increased the latency and reduced the probability to get to the reward, but only in pigs exposed to barren conditions in early life, which thus were more sensitive to reward loss than pigs from enriched early life housing. In conclusion, barren housed pigs seemed overall less motivated for the reward, and early life housing conditions had long-term effects on the sensitivity to reward loss.

Effects of early and later life environmental enrichment and personality on attention bias in pigs (Sus scrofa domesticus)

We investigated effects of early and later life housing on attention bias, as an indicator of affective state, in pigs differing in coping style [reactive (LR) vs. proactive (HR)]. Pigs (n = 128) in barren or enriched housing from birth (B1 vs. E1) that experienced either a switch in housing at 7 weeks of age or not (creating B1B2, B1E2, E1E2, and E1B2 treatments), were studied in a 180-s attention bias test at 11 weeks. Pigs exposed to a 10-s-auditory-and-sudden-motion threat in the test arena paid more attention to the location of the threat, were more vigilant, showed less eating, more walking and were more likely to utter high-pitched vocalisations than non-threat pigs. During threat presence, HR pigs from post-switch enriched housing (E2-HR, i.e., B1E2 + E1E2) showed more vigilance but less exploration than others. After threat removal, no effects were found on time spent paying attention to the threat, vigilance, and eating, but E2-HR pigs paid attention to the threat more frequently, were more likely to utter high-pitched vocalisations and walked more compared to (part of) other groups, suggesting the most negative affective state in these animals. E2 pigs grunted more than B2 pigs. Thus, current housing, but not early life housing, affected behaviour in a personality-dependent manner in this attention bias test. Housing effects were opposite to expectation, possibly due to the short-term effect of the relative contrast between the home pens of the pigs and the test room. This potentially overruled putative long-term effects of environmental conditions on attention bias.

What is animal happiness?

Today, we see a growing concern for the quality of life of nonhuman animals and an accompanying call for viable means of assessing how well animals thrive. Past research focused on minimizing negatives such as stress, while more recent endeavors strive to promote positives such as happiness. But what is animal happiness? Although often mentioned, the term lacks a clear definition. With recent advances in the study of animal emotion, current interest into positive rather than negative experiences, and the call for captive and domesticated animals to have good lives, the time is ripe to examine the concept of animal happiness. We draw from the human and animal literature to delineate a concept of animal happiness and propose how to assess it. We argue that animal happiness depends on how an individual feels generally-that is, a typical level of affect.

Assessing the External Validity of Successive Negative Contrast - Implications for Animal Welfare

When unexpectedly switched from a preferred to a less-preferred food reward, non-human animals may decrease consumption below that when only receiving the less-preferred reward - a successive negative contrast (SNC) effect. SNC has been proposed as an animal welfare indicator, however, to be effective it should show external validity; being demonstrable outside of highly standardized laboratory settings. We therefore investigated whether the SNC effect typically shown in laboratory rats was observed in owned (pet) rats from heterogeneous non-laboratory environments. Subjects (N = 14) were tested in a consummatory SNC paradigm with solid food rewards. "Shifted" rats received a high-value reward for 10 days (pre-shift), a low-value reward for six days (post-shift), then one additional day of high-value reward (re-shift). "Unshifted" rats always received the same low-value reward. "Shifted" rats consumed more food during pre-shift and re-shift trials, but ate less of the low-value food than "unshifted" animals in the post-shift trials - a SNC effect. This confirms the external validity of the SNC paradigm, extending reproducibility to outside the laboratory, indicating translatability across contexts, thus enhancing its potential use as a welfare indicator.

Do dogs experience frustration? New contributions on successive negative contrast in domestic dogs (Canis familiaris)

An unexpected change in reward quantity or quality frequently elicits a sharp decrease of responses as well as a negative emotional state. This phenomenon is called successive negative contrast (SNC) and, although it has been observed in numerous mammals, results in dogs have been inconsistent. The aim of this study was to evaluate SNC in dogs, comparing the effects of rewards of different qualities in a non-social task carried out in the dogs' usual environment. Dogs were separated into two experimental groups that experienced a downshift from a high quality reward (liver or sausage) to a low quality one (dry food), as well as a control group that always received dry food. The task involved a dog toy with bone shaped pieces that had to be removed to get the food hidden underneath. When the reward changed from liver to dry food, dogs picked up significantly fewer bones than the control group. However, this effect was not observed with sausage. Results show SNC in dogs in a non-social task carried out in their home environment. Additionally, the importance of the discrepancy in the hedonic value of the rewards is highlighted.

Behavioural responses to unexpected changes in reward quality

Successive negative contrast (SNC) effects are changes in anticipatory or consummatory behaviour when animals unexpectedly receive a lower value reward than they have received previously. SNC effects are often assumed to reflect frustration and appear to be influenced by background affective state. However, alternative explanations of SNC, such as the functional-search hypothesis, do not necessarily imply an aversive affective state. We tested 18 dogs in a SNC paradigm using a patch foraging task. Dogs were tested in two conditions, once with the low value reward in all of five trials (unshifted) and once when reward value was altered between high and low (shifted). Following a reward downshift, subjects showed a SNC effect by switching significantly more often between patches compared to the unshifted condition. However, approach latency, foraging time and quantity consumed did not differ between conditions, suggesting non-affective functional search behaviour rather than frustration. There was no relationship between strength of SNC and anxiety-related behaviours as measured in a novel object test and a personality questionnaire (C-BARQ). However, associations with the C-BARQ scores for Trainability and Stranger directed aggression suggest a possible link with behavioural flexibility and coping style. While reward quality clearly affects incentive motivation, the relationship between SNC, frustration and background affective state requires further exploration.

Methods for Investigating the Motivation of Mice to Explore and Access Food Rewards

The emotional state of domestic animals is an essential component of the assessment of their welfare. In addition, sensitivity to various rewards can be a valuable indicator when investigating these states. We aimed to design an exploration test and a contrast test that did not evoke fear and anxiety in C57BL/6N mice but that instead were perceived as positive experiences and that might be used to assess sensitivity to various rewards. The exploratory arena had a larger central area and 8 smaller sections containing various objects. Motivation (measured as latency to enter the arena under conditions of increasing weight of the entrance door), anticipation (measured as latency to enter the arena under conditions of increasing delay in opening the entrance door), and the numbers of visits to the different sections were evaluated during a 5-min session in the arena. In the contrast test, after traversing a runway, half of the mice received a tasty reward (hazelnut cream), whereas the others received a neutral reward (food pellet) at the far end. Latency to reach the reward was recorded. After baseline training, rewards were swapped for half of the mice from each category for 3 d, to establish a negative and positive contrast. Mice were both motivated and showed anticipation to enter the exploration arena; after entering, they were active and visited many sections. In the contrast test, latency during the baseline period was longer for mice given the neutral reward compared with the tasty reward. Compared with baseline, latency during the postshift phase decreased for the positive-contrast group (neutral-tasty reward pattern) but did not differ for the negative-contrast group (tasty-neutral reward pattern). Overall, both tests seemed to be positive experiences for the mice and showed potential for use to investigate reward sensitivity.

Dissociating the effects of alternative early-life feeding schedules on the development of adult depression-like phenotypes

Early-life adversity is associated with increased vulnerability to depression in humans, and depression-like phenotypes in animals. However, different types of adverse experience may leave different signatures in adulthood. We experimentally manipulated the Amount of food delivered to European starling nestlings and the begging Effort required to obtain food during early development. Here, we report behavioural data in adulthood from a task that assessed sensitivity to shifts in reward magnitude characteristic of depression-like low mood. Birds that had experienced Hard Effort were more food motivated than birds that had experienced Easy Effort. Both Effort and Amount affected sensitivity to shifts in reward magnitude: Hard Effort birds showed an enhanced negative contrast effect following loss of reward ('disappointment'), and Lean Amount birds failed to show a normal positive contrast effect following gain in reward (a lack of 'elation'). Therefore, the feeding schedule experienced for just 10 days in early life caused enduring effects on feeding motivation and sensitivity to reward loss/gain consistent with human depression. Furthermore, the contrast effects were specific to different types of adversity. These results highlight the importance of early-life feeding schedules in the development of depression-like phenotypes.

You know what? I'm happy. Cognitive bias is not related to personality but is induced by pair-housing in canaries (Serinus canaria)

Recent studies suggest that cognitive bias could constitute a novel and valid measure of animal welfare. Although interest for a link between personality and cognition is growing, no study to date investigated whether a cognitive bias might be related to the personality of the individuals. We trained 43 domestic canaries (Serinus canaria) to discriminate between two sides of a test cage, each side being associated with a different value (attractive or aversive food in a dish). During the test phase, the dish was placed at intermediate locations, representing ambiguous information. Results show evidence of an "optimistic" bias (flying faster to the dish at the ambiguous location) in birds housed in pairs, compared to birds housed singly, suggesting an influence of social context (living conditions) on canaries' emotions when tested individually. We also studied six traits of individuals' personality and found that aggressiveness, neophobia, one sociability index and obstinacy were repeatable across social context and/or day-light schedule, whereas the other sociability index, boldness and locomotion were not. No correlation between the birds' optimism and any of their personality traits was found, suggesting that cognitive bias may be a matter of social context rather than of individual personality.

Training Reduces Stress in Human-Socialised Wolves to the Same Degree as in Dogs

The welfare of animals in captivity is of considerable societal concern. A major source of stress, especially for wild animals, is the lack of control over their environment, which includes not being able to avoid contact with human beings. Paradoxically, some studies have shown that interactions with human beings may improve the welfare of wild animals in captivity. Here, we investigated the behavioural (behaviours indicative of cooperation or stress) and physiological (variations in salivary cortisol concentrations) effects of the increasingly used practice of training wild animals as a way to facilitate handling and/or as behavioural enrichment. We evaluated the effects of indoor training sessions with familiar caretakers on nine human-socialised individuals of a wild species, the wolf (Canis lupus), in comparison to nine individuals of its domesticated form, the dog (Canis lupus familiaris). All animals were raised and kept in intraspecific packs under identical conditions-in accordance with the social structure of the species-in order to control for socialisation with human beings and familiarity with training. We also collected saliva samples of trainers to measure GC and testosterone concentrations, to control for the effects of trainers' stress levels on the responses of the animals. During the training sessions, separated from pack members, the animals stayed voluntarily close to the trainers and mostly adequately performed requested behaviours, indicating concentration to the task. Similarly to dogs, the salivary cortisol level of wolves-used as an index of stress-dropped during these sessions, pointing to a similar stress-reducing effect of the training interaction in both subspecies. The responses to the requested behaviours and the reduction in salivary cortisol level of wolves and dogs varied across trainers, which indicates that the relaxing effect of training has a social component. This points to another factor affecting the welfare of animals during the sessions, beside the rewarding effect of getting food and control over the situation by successfully completing a task. As all responses performed by the animals corresponded to cues already familiar to them, the reported effects were likely due to the above cited factors rather than to a learning process. Our results support previous findings suggesting that training is a potentially powerful tool for improving welfare in some wild social canids by creating structured and positive interactions between these animals and their human caretakers.

Emotion Evaluation and Response Slowing in a Non-Human Primate: New Directions for Cognitive Bias Measures of Animal Emotion?

The cognitive bias model of animal welfare assessment is informed by studies with humans demonstrating that the interaction between emotion and cognition can be detected using laboratory tasks. A limitation of cognitive bias tasks is the amount of training required by animals prior to testing. A potential solution is to use biologically relevant stimuli that trigger innate emotional responses. Here; we develop a new method to assess emotion in rhesus macaques; informed by paradigms used with humans: emotional Stroop; visual cueing and; in particular; response slowing. In humans; performance on a simple cognitive task can become impaired when emotional distractor content is displayed. Importantly; responses become slower in anxious individuals in the presence of mild threat; a pattern not seen in non-anxious individuals; who are able to effectively process and disengage from the distractor. Here; we present a proof-of-concept study; demonstrating that rhesus macaques show slowing of responses in a simple touch-screen task when emotional content is introduced; but only when they had recently experienced a presumably stressful veterinary inspection. Our results indicate the presence of a subtle “cognitive freeze” response; the measurement of which may provide a means of identifying negative shifts in emotion in animals.

A reappraisal of successive negative contrast in two populations of domestic dogs

When an anticipated food reward is unexpectedly reduced in quality or quantity, many mammals show a successive negative contrast (SNC) effect, i.e. a reduction in instrumental or consummatory responses below the level shown by control animals that have only ever received the lower-value reward. SNC effects are believed to reflect an aversive emotional state, caused by the discrepancy between the expected and the actual reward. Furthermore, how animals respond to such discrepancy has been suggested to be a sign of animals’ background mood state. However, the occurrence and interpretation of SNC effects are not unequivocal, and there is a relative lack of studies conducted outside of laboratory conditions. Here, we tested two populations of domestic dogs (24 owned pet dogs and 21 dogs from rescue kennels) in a SNC paradigm following the methodology by Bentosela et al. (J Comp Psychol 123:125–130, 2009), using a design that allowed a within-, as well as a between-, subjects analysis. We found no evidence of a SNC effect in either population using a within- or between-subjects design. Indeed, the within-subjects analysis revealed a reverse SNC effect, with subjects in the shifted condition showing a significantly higher level of response, even after they received an unexpected reduction in reward quality. Using a within-, rather than a between-, subjects design may be beneficial in studies of SNC due to higher sensitivity and statistical power; however, order effects on subject performance need to be considered. These results suggest that this particular SNC paradigm may not be sufficiently robust to replicate easily in a range of environmental contexts and populations.

Frontal Brain Activity and Behavioral Indicators of Affective States are Weakly Affected by Thermal Stimuli in Sheep Living in Different Housing Conditions

Many stimuli evoke short-term emotional reactions. These reactions may play an important role in assessing how a subject perceives a stimulus. Additionally, long-term mood may modulate the emotional reactions but it is still unclear in what way. The question seems to be important in terms of animal welfare, as a negative mood may taint emotional reactions. In the present study with sheep, we investigated the effects of thermal stimuli on emotional reactions and the potential modulating effect of mood induced by manipulations of the housing conditions. We assume that unpredictable, stimulus-poor conditions lead to a negative and predictable, stimulus-rich conditions to a positive mood state. The thermal stimuli were applied to the upper breast during warm ambient temperatures: hot (as presumably negative), intermediate, and cold (as presumably positive). We recorded cortical activity by functional near-infrared spectroscopy, restlessness behavior (e.g., locomotor activity, aversive behaviors), and ear postures as indicators of emotional reactions. The strongest hemodynamic reaction was found during a stimulus of intermediate valence independent of the animal's housing conditions, whereas locomotor activity, ear movements, and aversive behaviors were seen most in sheep from the unpredictable, stimulus-poor housing conditions, independent of stimulus valence. We conclude that, sheep perceived the thermal stimuli and differentiated between some of them. An adequate interpretation of the neuronal activity pattern remains difficult, though. The effects of housing conditions were small indicating that the induction of mood was only modestly efficacious. Therefore, a modulating effect of mood on the emotional reaction was not found.

Psychopharmacological characterisation of the successive negative contrast effect in rats

RATIONALE

Successive negative contrast (SNC) describes a change in the behaviour of an animal following a downshift in the quantitative or qualitative value of an expected reward. This behavioural response has been hypothesised to be linked to affective state, with negative states associated with larger and/or prolonged shifts in behaviour.

OBJECTIVE

This study has investigated whether different psychopharmacological treatments have dissociable actions on the SNC effect in rats and related these findings to their actions on different neurotransmitter systems and affective state.

METHODS

Animals were trained to perform a nose-poke response to obtain a high-value food reward (four pellets). SNC was quantified during devalue sessions in which the reward was reduced to one pellet. Using a within-subject study design, the effects of acute treatment with anxiolytic, anxiogenic, antidepressant and dopaminergic drugs were investigated during both baseline (four pellets) or devalue sessions (one pellet).

RESULTS

The indirect dopamine agonist, amphetamine, attenuated the SNC effect whilst the D1/D2 antagonist, alpha-flupenthixol, potentiated it. The antidepressant citalopram, anxiolytic buspirone and anxiogenic FG7142 had no specific effects on SNC, although FG7142 induced general impairments at higher doses. The α2-adrenoceptor antagonist, yohimbine, increased premature responding but had no specific effect on SNC. Results for the anxiolytic diazepam were mixed with one group showing an attenuation of the SNC effect whilst the other showed no effect.

CONCLUSIONS

These data suggest that the SNC effect is mediated, at least in part, by dopamine signalling. The SNC effect may also be attenuated by benzodiazepine anxiolytics.

Canine sense and sensibility: tipping points and response latency variability as an optimism index in a canine judgement bias assessment

Recent advances in animal welfare science used judgement bias, a type of cognitive bias, as a means to objectively measure an animal's affective state. It is postulated that animals showing heightened expectation of positive outcomes may be categorised optimistic, while those showing heightened expectations of negative outcomes may be considered pessimistic. This study pioneers the use of a portable, automated apparatus to train and test the judgement bias of dogs. Dogs were trained in a discrimination task in which they learned to touch a target after a tone associated with a lactose-free milk reward and abstain from touching the target after a tone associated with water. Their judgement bias was then probed by presenting tones between those learned in the discrimination task and measuring their latency to respond by touching the target. A Cox's Proportional Hazards model was used to analyse censored response latency data. Dog and Cue both had a highly significant effect on latency and risk of touching a target. This indicates that judgement bias both exists in dogs and differs between dogs. Test number also had a significant effect, indicating that dogs were less likely to touch the target over successive tests. Detailed examination of the response latencies revealed tipping points where average latency increased by 100% or more, giving an indication of where dogs began to treat ambiguous cues as predicting more negative outcomes than positive ones. Variability scores were calculated to provide an index of optimism using average latency and standard deviation at cues after the tipping point. The use of a mathematical approach to assessing judgement bias data in animal studies offers a more detailed interpretation than traditional statistical analyses. This study provides proof of concept for the use of an automated apparatus for measuring cognitive bias in dogs.

Searching for behavioral indicators of welfare in zoos: uncovering anticipatory behavior

A current focus of zoo-based research aims to identify indicators of animal welfare. Reliable behavioral indicators of welfare are highly desirable as behavioral observation is non invasive and requires little in the way of specialized equipment and other costly resources-save for observer time. Anticipatory behavior is an indicator of an animal's sensitivity to reward and as such, it is a real-time indicator of animals' own perceptions of their well-being. In fact, anticipatory behavior may generate a positive affective state and thus be at least a brief manifestation of good welfare itself. The husbandry conditions of most captive animals are such that food acquisition and other positive outcomes are highly scheduled and easily signaled. These conditions promote the development of anticipatory behavior, yet little research has either documented or interpreted this behavior in zoo and aquarium animals. This commentary suggests that anticipatory behavior could be a useful tool for assessing welfare and calls upon zoo and aquarium researchers to begin to develop this tool by describing the behavior and the circumstances that lead to its modulation.

How enrichment affects exploration trade-offs in rats: implications for welfare and well-being

We propose that a comparative approach to well-being could be the key to understanding ‘the good life.’ Inspired by current theories of human well-being and animal welfare, we designed a novel test of exploration behavior. Environmentally and socially enriched Long-Evans female rats (N = 60) were trained in four simultaneously presented arms of an eight-arm radial-maze. They learned to expect successes in two arms and failures in the other two. After training, 20 animals remained in enriched housing (enrichment-maintenance) while 40 animals were re-housed in standard, isolated conditions (enrichment-removal). Two weeks later, all animals were re-tested in the maze, initially with access to the four familiar arms only. In the final minute, they also had access to the unfamiliar ambiguous-arms. Though both groups showed significant interest in the ambiguous-arms (P<.0001), the enrichment-maintenance group showed a significantly greater exploratory tendency (P<.01) despite having equivalent levels of activity (P>.3). Thus, we show not only that rats will abandon known rewards and incur risk in order to explore, indicating that exploration is valuable in its own right, but also that individuals with (vs. without) enriched housing conditions are more likely to engage in such exploratory behavior. This novel test contributes to the body of knowledge examining the importance of exploration in humans and other animals; implications for animal welfare and human well-being are discussed.