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de Boyer des Roches, A., Durier, V., Richard-Yris, M. - A., Blois-Heulin, C., Ezzaouïa, M., Hausberger, M., et al. (2011). Differential outcomes of unilateral interferences at birth. Biology Letters, 7(2), 177–180.
Abstract: Behavioural modifications, including modifications of emotional reactivity, can occur following early experience such as handling (manual rubbing). Here, we investigated the effects of unilateral tactile stimulation at an early stage on emotional reactions later on. We handled newborn foals intensively on one side of their body. This early unilateral tactile experience had medium-term effects: the reactions of foals to a human approach, when they were 10 days old, differed according to the side stimulated at birth. Fewer right-handled foals accepted contact with humans, they delayed first contact longer and they evaded approaching humans sooner than did non-handled and left-handled foals. These results raise questions concerning the organization of neonatal care in animals and humans.
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Sankey, C., Henry, S., André, N., Richard-Yris, M. - A., & Hausberger, M. (2011). Do Horses Have a Concept of Person? PLoS ONE, 6(3), e18331 EP -.
Abstract: <sec> <title>Background</title> <p>Animals' ability for cross-modal recognition has recently received much interest. Captive or domestic animals seem able to perceive cues of human attention and appear to have a multisensory perception of humans.</p> </sec> <sec> <title>Methodology/Principal Findings</title> <p>Here, we used a task where horses have to remain immobile under a vocal order to test whether they are sensitive to the attentional state of the experimenter, but also whether they behave and respond differently to the familiar order when tested by a familiar or an unknown person. Horses' response varied according to the person's attentional state when the order was given by an unknown person: obedience levels were higher when the person giving the order was looking at the horse than when he was not attentive. More interesting is the finding that whatever the condition, horses monitored much more and for longer times the unknown person, as if they were surprised to hear the familiar order given by an unknown voice.</p> </sec> <sec> <title>Conclusion/Significance</title> <p>These results suggest that recognition of humans may lie in a global, integrated, multisensory representation of specific individuals, that includes visual and vocal identity, but also expectations on the individual's behaviour in a familiar situation.</p> </sec>
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Fureix, C., Jego, P., Henry, S., Lansade, L., & Hausberger, M. (2012). Towards an Ethological Animal Model of Depression? A Study on Horses. PLoS ONE, 7(6), e39280 EP -.
Abstract: <sec><title>Background</title><p>Recent reviews question current animal models of depression and emphasise the need for ethological models of mood disorders based on animals living under natural conditions. Domestic horses encounter chronic stress, including potential stress at work, which can induce behavioural disorders (<italic>e.g.</italic> “apathy”). Our pioneering study evaluated the potential of domestic horses in their usual environment to become an ethological model of depression by testing this models’ face validity (<italic>i.e.</italic> behavioural similarity with descriptions of human depressive states).</p></sec><sec><title>Methodology/Principal Findings</title><p>We observed the spontaneous behaviour of 59 working horses in their home environment, focusing on immobility bouts of apparent unresponsiveness when horses displayed an atypical posture (termed <italic>withdrawn</italic> hereafter), evaluated their responsiveness to their environment and their anxiety levels, and analysed cortisol levels. Twenty-four percent of the horses presented the withdrawn posture, also characterized by gaze, head and ears fixity, a profile that suggests a spontaneous expression of “behavioural despair”. When compared with control “non-withdrawn” horses from the same stable, withdrawn horses appeared more indifferent to environmental stimuli in their home environment but reacted more emotionally in more challenging situations. They exhibited lower plasma cortisol levels. Withdrawn horses all belonged to the same breed and females were over-represented.</p></sec><sec><title>Conclusions/Significance</title><p>Horse might be a useful potential candidate for an animal model of depression. Face validity of this model appeared good, and potential genetic input and high prevalence of these disorders in females add to the convergence. At a time when current animal models of depression are questioned and the need for novel models is expressed, this study suggests that novel models and biomarkers could emerge from ethological approaches in home environments.</p></sec>
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Rochais, C., HENRY, S., Sankey, C., Nassur, F., Gorecka-Bruzda, A., & HAUSBERGER, M. (2014). Visual attention, an indicator of human-animal relationships? A study of domestic horses (Equus caballus). Frontiers in Psychology, 5.
Abstract: BACKGROUND: As visual attention is an intrinsic part of social relationships, and because relationships are built on a succession of interactions, their establishment involves learning and attention. The emotional, rewarding or punishing, content can modulate selective attention. In horses, the use of positive/negative reinforcement during training determines short and long-term human-horse relationships. In a recent study in horses, where either food or withers' grooming were used as a reward, it appeared that only the food-rewarded horses learned the task and show better relationship with humans. In the present study, we hypothesized that this differential effect of grooming/food rewards on learning performances could be due to attentional processes. Monitoring, gazes and behaviors directed towards the trainer revealed that the use of a food reward (FR) as positive reinforcement increased horses' selective attention towards their trainer. Conversely, horses trained with grooming reward (GR) expressed more inattentive responses and did not show a decrease of “agitated” behavior. However, individual plotting of attention vs. rate of learning performances revealed a complex pattern. Thus, while all FR horses showed a “window” of attention related to faster learning performances, GR horses' pattern followed an almost normal curve where the extreme animals (i.e., highest and lowest attention) had the slowest learning performances. On the other hand, learning was influenced by attention: at the end of training, the more attentive horses had also better learning performances. This study, based on horses, contributes to the general debate on the place of attentional processes at the interface of emotion and cognition and opens new lines of thought about individual sensitivities (only individuals can tell what an appropriate reward is), attentional processes and learning.
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Pawluski, J., Jego, P., Henry, S., Bruchet, A., Palme, R., Coste, C., et al. (2017). Low plasma cortisol and fecal cortisol metabolite measures as indicators of compromised welfare in domestic horses (Equus caballus). Plos One, 12(9), e0182257.
Abstract: The hypothalamic-pituitary-adrenal (HPA) axis response to chronic stress is far from straight forward, particularly with regards to animal welfare. There are reports of no effect as well as both decreases and increases in cortisol after chronic stressors. Therefore, the first aim of the present study was to determine how measures of compromised welfare, such as chronic pain and haematological anomalies, related to cortisol levels in domestic horses (Equus caballus). Domestic horses are an informative model to investigate the impact of chronic stress (due to environment, pain, work, housing conditions...) on the HPA axis. The second aim was to determine whether levels of fecal cortisol metabolites (FCM) may be used as an indicator of welfare measures. The present study used fifty-nine horses (44 geldings and 15 mares), from three riding centres in Brittany, France. The primary findings show that horses whose welfare was clearly compromised (as indicated by an unusual ears backward position, presence of vertebral problems or haematological anomalies, e.g. anaemia) also had lower levels of both FCM and plasma cortisol. This work extends our previous findings showing that withdrawn postures, indicators of depressive-like behavior in horses, are associated with lower plasma cortisol levels. We also found that evening plasma cortisol levels positively correlated with FCM levels in horses. Future research aims to determine the extent to which factors of influence on welfare, such as living conditions (e.g. single stalls versus group housing in pasture or paddocks), early life factors, and human interaction, act as mediators of cortisol levels in horses.
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Henry, S., Fureix, C., Rowberry, R., Bateson, M., & Hausberger, M. (2017). Do horses with poor welfare show 'pessimistic' cognitive biases? Sci. Nat., 104(1), 8.
Abstract: This field study tested the hypothesis that domestic horses living under putatively challenging-to-welfare conditions (for example involving social, spatial, feeding constraints) would present signs of poor welfare and co-occurring pessimistic judgement biases. Our subjects were 34 horses who had been housed for over 3 years in either restricted riding school situations (e.g. kept in single boxes, with limited roughage, ridden by inexperienced riders; N = 25) or under more naturalistic conditions (e.g. access to free-range, kept in stable social groups, leisure riding; N = 9). The horses' welfare was assessed by recording health-related, behavioural and postural indicators. Additionally, after learning a location task to discriminate a bucket containing either edible food ('positive' location) or unpalatable food ('negative' location), the horses were presented with a bucket located near the positive position, near the negative position and halfway between the positive and negative positions to assess their judgement biases. The riding school horses displayed the highest levels of behavioural and health-related problems and a pessimistic judgment bias, whereas the horses living under more naturalistic conditions displayed indications of good welfare and an optimistic bias. Moreover, pessimistic bias data strongly correlated with poor welfare data. This suggests that a lowered mood impacts a non-human species' perception of its environment and highlights cognitive biases as an appropriate tool to assess the impact of chronic living conditions on horse welfare.
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Henry, S., Richard-Yris, M. - A., & Hausberger, M. (2006). Influence of various early human-foal interferences on subsequent human-foal relationship. Dev Psychobiol, 48(8), 712–718.
Abstract: Whereas the way animals perceive human contact has been particularly examined in pet animals, a small amount of investigations has been done in domestic ungulates. It was nevertheless assumed that, as pet animals, non-aggressive forms of tactile contact were as well rewarding or positive for these species, even though the features of intraspecific relationships in pet animals and domestic ungulates may be to some extent different.We test here the hypothesis that horses may not consider physical handling by humans as a positive event. When comparing different early human-foal interactions, we found that early exposure to a motionless human enhanced slightly foals reactions to humans whereas forced stroking or handling in early life did not improve later human-foal relation. Foals that were assisted during their first suckling (e.g., brought to the dam's teat) even tended to avoid human approach at 2 weeks, and physical contact at 1 month of age.We argue that interspecies differences may exist in how tactile stimulation is perceived. It may be important for the establishment of a bond that a young animal is active in the process and able, through its behavioral responses, to help define what is positive for it. This way of investigation may have important general implications in how we consider the development of social relations, both within and between species.
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De Boyer Des Roches, A., Richard-Yris, M. - A., Henry, S., Ezzaouia, M., & Hausberger, M. (2008). Laterality and emotions: visual laterality in the domestic horse (Equus caballus) differs with objects' emotional value. Physiol. Behav., 94(3), 487–490.
Abstract: Lateralization of emotions has received great attention in the last decades, both in humans and animals, but little interest has been given to side bias in perceptual processing. Here, we investigated the influence of the emotional valence of stimuli on visual and olfactory explorations by horses, a large mammalian species with two large monocular visual fields and almost complete decussation of optic fibres. We confronted 38 Arab mares to three objects with either a positive, negative or neutral emotional valence (novel object). The results revealed a gradient of exploration of the 3 objects according to their emotional value and a clear asymmetry in visual exploration. When exploring the novel object, mares used preferentially their right eyes, while they showed a slight tendency to use their left eyes for the negative object. No asymmetry was evidenced for the object with the positive valence. A trend for an asymmetry in olfactory investigation was also observed. Our data confirm the role of the left hemisphere in assessing novelty in horses like in many vertebrate species and the possible role of the right hemisphere in processing negative emotional responses. Our findings also suggest the importance of both hemispheres in the processing positive emotions. This study is, to our knowledge, the first to demonstrate clearly that the emotional valence of a stimulus induces a specific visual lateralization pattern.
Keywords: Animals; Animals, Newborn; Behavior, Animal/physiology; Dominance, Ocular/*physiology; *Emotions; Exploratory Behavior/physiology; Female; Horses/*physiology; Olfactory Pathways/physiology; Pattern Recognition, Visual/*physiology; Photic Stimulation; Pregnancy; Statistics, Nonparametric; Visual Fields/physiology
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Sankey, C., Richard-Yris, M. - A., Leroy, H., Henry, S., & Hausberger, M. (2010). Positive interactions lead to lasting positive memories in horses, Equus caballus. Anim. Behav., 79(4), 869–875.
Abstract: Social relationships are important in social species. These relationships, based on repeated interactions, define each partner's expectations during the following encounters. The creation of a relationship implies high social cognitive abilities which require that each partner is able to associate the positive or negative content of an interaction with a specific partner and to recall this association. In this study, we tested the effects of repeated interactions on the memory kept by 23 young horses about humans, after 6 and 8 months of separation. The association of a reward with a learning task in an interactional context induced positive reactions towards humans during training. It also increased contact and interest, not only just after training, but also several months later, despite no further interaction with humans. In addition, this ‘positive memory’ of humans extended to novel persons. Overall, positive reinforcement enhanced learning and memorization of the task itself. These findings suggest remarkable social cognitive abilities that can be transposed from intraspecific to interspecific social contexts.
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Bourjade, M., Moulinot, M., Henry, S., & Richard-Yris, M. - A. H. M. (2008). Could Adults be Used to Improve Social Skills of Young Horses, Equus caballus? Ethology, 50(4), 408–417.
Abstract: We investigated the effects of the introduction of foreign adults on the behavior of young horses. First, we observed the behavior of 1- and 2-year-old domestic horses housed in same-age and same-sex groups (a standard housing system, but different from a natural situation). Then, two same-sex adults were introduced into each experimental group. Observations made before, during and after an introduction indicated that young horses reared in homogeneous groups of young had different behaviors compared to other domestic horses reared under more socially natural conditions. After the introduction of adults, young horses expressed new behaviors, preferential social associations emerged, positive social behavior increased and agonistic interactions decreased. These results have important implications both for understanding the influence that adults may have on the behavior of young horses, and in terms of husbandry, indicating the importance of keeping young horses with adults, although further studies are still necessary. © 2008 Wiley Periodicals, Inc. Dev Psychobiol 50: 408-417, 2008.
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