Perseverative responding and the aetiology of equine oral stereotypy

La Tène Horse Remains from Alba Iulia CX 143 Complex: A Whole Story to Tell

The present paper deals with the archaeozoological investigation carried out on a horse skeleton discovered in a Late Iron Age La Tène tomb (coded CX 143) in Alba Iulia, Romania. The paper presents all the results of the investigation, with a description of finds, adding a detailed assessment of the dentition with some interesting conclusions on the usage of a horse bit and the possible consequences of this use. The morphological features of the horse indicate a 7-8-year-old male individual, with a recalculated height of 1200-1300 mm. What is also stressed in the investigated sample is the lack of the characteristic pathological lesions typical for horseback riding but showing distinctive elements of bit wear. A comparative perspective over the few findings from the same period is provided to ensure the framing of the identified individual into the much larger historical context.

Habit Formation and the Effect of Repeated Stress Exposures on Cognitive Flexibility Learning in Horses

Horse training exposes horses to an array of cognitive and ethological challenges. Horses are routinely required to perform behaviours that are not aligned to aspects of their ethology, which may delay learning. While horses readily form habits during training, not all of these responses are considered desirable, resulting in the horse being subject to retraining. This is a form of cognitive flexibility and is critical to the extinction of habits and the learning of new responses. It is underpinned by complex neural processes which can be impaired by chronic or repeated stress. Domestic horses may be repeatedly exposed to multiples stressors. The potential contribution of stress impairments of cognitive flexibility to apparent training failures is not well understood, however research from neuroscience can be used to understand horses’ responses to training. We trained horses to acquire habit-like responses in one of two industry-style aversive instrumental learning scenarios (moving away from the stimulus-instinctual or moving towards the stimulus-non-instinctual) and evaluated the effect of repeated stress exposures on their cognitive flexibility in a reversal task. We measured heart rate as a proxy for noradrenaline release, salivary cortisol and serum Brain Derived Neurotrophic Factor (BDNF) to infer possible neural correlates of the learning outcomes. The instinctual task which aligned with innate equine escape responses to aversive stimuli was acquired significantly faster than the non-instinctual task during both learning phases, however contrary to expectations, the repeated stress exposure did not impair the reversal learning. We report a preliminary finding that serum BDNF and salivary cortisol concentrations in horses are positively correlated. The ethological salience of training tasks and cognitive flexibility learning can significantly affect learning in horses and trainers should adapt their practices where such tasks challenge innate equine behaviour.

Horses’ attentional characteristics differ according to the type of work

Attention is a central process of cognition and influences the execution of daily tasks. In humans, different types of work require different attentional skills and sport performance is associated with the ability to attention shift. Attention towards humans varies in dogs used for different types of work. Whether this variation is due to the recruitment of individuals suitable for specific types of work, or to the characteristics of the work, remains unclear. In the present study, we hypothesized that domestic horses (Equus caballus) trained for different types of work would also demonstrate different attentional characteristics but we also explored other possible factors of influence such as age, sex and breed. We exposed more than sixty horses, working in 4 different disciplines, and living in two types of housing conditions, to a visual attention test (VAT) performed in the home environment. Individual attentional characteristics in the test were not significantly influenced by age, sex, breed or conditions of life but were strongly related to the type of work. Riding school horses showed longer sequences and less fragmented attention than all other horses, including sport horses living in the same conditions. Interestingly, sport performance was correlated with attention fragmentation during the test in eventing horses, which may need more attention shifting during the competitions. Working conditions may influence attention characteristics indirectly through welfare, or directly through selection and training. Our study opens new lines of thought on the determinants of animal cognition and its plasticity and constitutes a further step towards understanding the interrelationship between working conditions and cognition.

The impulsive horse: comparing genetic, physiological and behavioral indicators to that of human addiction

Stress and genotype elicit changes in impulse control in a range of species that are attributable to adaptations in both the central and peripheral nervous system. We examined aspects of this mechanism in the horse by assessing the effect of a dopamine receptor genotype (DRD4) and central dopaminergic tone (measured via spontaneous blink rate [SBR] and behavioral initiation rate [BIR]), on measures of impulsivity, compulsivity (3-choice serial reaction time task) and sympathetic/ parasympathetic system balance (heart rate variability [HRV]). Genotype did not have a significant effect on any of the parameters measured. SBR but not BIR correlated significantly with levels of impulsivity. There was no clear association of HRV parameters with either measures of central dopaminergic activity or impulsivity/compulsivity. Overall, some elements of the data suggest that the horse may be a useful animal model for assessing the genetic and environmental factors that lead to the physiological and behavioral phenotype of human addiction, particularly when considering the relationship between central dopaminergic tone and impulsivity.

Effects of hay provision and presentation on cognitive development in dairy calves

In the dairy industry, feeding management has considerable influence on calf behavioral development, yet there is limited understanding of how aspects of diet or accommodating more varied feeding behavior may affect cognitive development in young calves. The objective of this study was to evaluate effects of provision and presentation of hay on the cognitive ability of pre-weaned dairy calves. Individually-housed Holstein heifer calves were assigned at birth to 1 of 3 treatments: pelleted starter only (n = 10), hay (chopped to 5 cm) and starter provided in separate buckets (n = 12), or hay and starter offered as a mixture (n = 11). During week 5 of age, calves were tested daily in a learning task consisting of a T-maze with a milk reward (0.2 L milk) placed in one arm. Calves were subjected to an initial learning and reversal learning stage, where the reward location was changed to the opposite arm of the maze. Calves received 5 sessions/d until they met learning criterion (moving directly to correct side in 3 consecutive sessions) for initial and reversal learning. Dietary treatment did not affect pass rate or the number of sessions required to pass the initial learning stage. During the reversal learning stage, calves provided only starter had a lower pass rate (0.038, during first 8 testing session) early during testing than calves provided hay separately (0.20; P = 0.020) and tended to have a lower pass rate than calves provided hay as a mixture (0.14; P = 0.057). Calves provided only starter also tended to require more sessions to meet the learning criterion (15.8) than both calves provided hay separately (10.8; P = 0.089) and as a mixture (11.8; P = 0.10). Calves provided hay also kicked less and spent more time sniffing or licking the testing area. The results of this experiment indicate that provision of hay may affect behavioral flexibility in dairy calves.

Domestic Foal Weaning: Need for Re-Thinking Breeding Practices?

Artificial weaning is a standard practice known to be one of the most stressful events in a domestic foal's life. Research has mainly focused on ways to alleviate weaning stress. However, there is still a need for more detailed research on what should constitute best practices with respect to animal welfare. The aim of this review is to address this issue by examining the natural weaning process. We first provide an overview of the scientific literature on the natural temporal dynamics of the dam-offspring bond in horses: it is to be noted that the natural process of weaning is little documented, individual variations have been poorly investigated and immediate effects of weaning on the mare-foal relationship remain unexplored. To partly address these gaps, we performed a study around the weaning period on 16 mare-foal pairs kept with minimal human interference. Most foals were weaned spontaneously when 9-10 months old, with individual variations mainly due to the conception rate of mares. Natural weaning induced no stress response in either partner and was performed without clear signs of rejection by the dams either just before or after. We lastly open up the discussion on the need for rethinking weaning practices under domestic conditions.

Equine Stereotaxtic Population Average Brain Atlas With Neuroanatomic Correlation

There is growing interest in the horse for behavioral, neuroanatomic and neuroscientific research due to its large and complex brain, cognitive abilities and long lifespan making it neurologically interesting and a potential large animal model for several neuropsychological diseases. Magnetic resonance imaging (MRI) is a powerful neuroscientific research tool that can be performed in vivo, with adapted equine facilities, or ex-vivo in the research setting. The brain atlas is a fundamental resource for neuroimaging research, and have been created for a multitude animal models, however, none currently exist for the equine brain. In this study, we document the creation of a high-resolution stereotaxic population average brain atlas of the equine. The atlas was generated from nine unfixed equine cadaver brains imaged within 4 h of euthanasia in a 3-tesla MRI. The atlas was generated using linear and non-linear registration methods and quality assessed using signal and contrast to noise calculations. Tissue segmentation maps (TSMs) for white matter (WM), gray matter (GM) and cerebrospinal fluid (CSF), were generated and manually segmented anatomic priors created for multiple subcortical brain structures. The resulting atlas was validated and correlated to gross anatomical specimens and is made freely available at as an online resource for researchers (https://doi.org/10.7298/cyrs-7b51.2). The mean volume metrics for the whole brain, GM and WM for the included subjects were documented and the effect of age and laterality assessed. Alterations in brain volume in relation to age were identified, though these variables were not found to be significantly correlated. All subjects had higher whole brain, GM and WM volumes on the right side, consistent with the well documented right forebrain dominance of horses. This atlas provides an important tool for automated processing in equine and translational neuroimaging research.

Mutual interactions between cognition and welfare: The horse as an animal model

Research in cognitive psychology has repeatedly shown how much cognition and emotions are mutually related to one another. Psychological disorders are associated with cognitive (attention, memory and judgment) biases and chronic pain may affect attention, learning or memory. Laboratory studies have provided useful insights about the processes involved but observations about spontaneous animal models, living in different stress/welfare conditions may help understand further how cognition and welfare are interrelated in the « real world ». Domestic horses constitute such a model as they live in a variety of conditions that impact differently their welfare state. In the present review, we try and provide an overview of the scientific literature on cognition and welfare of domestic horses and their interrelationship. We address how emotions and welfare may affect cognitive processes in horses and impact the way they perceive their environment (including work). We propose new methods for assessing the relationship between welfare and cognition and open up the discussion on the evolution of the brain and the part domestication may have played.

Neurophysiological correlates of stereotypic behaviour in a model carnivore species

Stereotypic behaviour (SB) is common in animals housed in farm, zoo or laboratory conditions, including captive Carnivora (e.g. wild ursids and felids). Neurobiological data on housing-induced SBs come from four species (macaques, two rodent species, and horses), and suggest basal ganglia (BG) dysfunction. We investigated whether similar patterns occur in Carnivora via a model, American mink, because their SB is distinctive in form and timing. We raised 32 males in non-enriched (NE) or enriched (E) cages for 2 years, and assessed two forms of SB: 1) Carnivora-typical locomotor-and-whole-body ('loco') SBs (e.g. pacing, weaving); 2) scrabbling with the forepaws. Neuronal activity was analysed via cytochrome oxidase (CO) staining of the dorsal striatum (caudate; putamen), globus pallidus (externus, GPe; internus, GPi), STN, and nucleus accumbens (NAc); and the GPe:GPi ratio (GPr) calculated to assess relative activation of direct and indirect pathways. NE mink stereotyped more, and had lower GPr CO-staining indicating relatively lower indirect pathway activation. However, no single BG area was affected by housing and nor did GPr values covary with SB. Independent of housing, elevated NAc CO-staining predicted more loco SB, while scrabbling, probably because it negatively correlated with loco SB, negatively covaried with NAc CO-staining in NE subjects. These results thus implicate the NAc in individual differences in mink SB. However, because they cannot explain why NE subjects showed more SB, they provide limited support for the BG dysfunction hypothesis for this species' housing-induced SB. More research is therefore needed to understand how barren housing causes SB in captive Carnivora.

Stereotypic horses (Equus caballus) are not cognitively impaired

Stereotypies in animals are thought to arise from an interaction between genetic predisposition and sub-optimal housing conditions. In domestic horses, a well-studied stereotypy is crib-biting, an abnormal behaviour that appears to help individuals to cope with stressful situations. One prominent hypothesis states that animals affected by stereotypies are cognitively less flexible compared to healthy controls, due to sensitization of a specific brain area, the basal ganglia. The aim of this study was to test this hypothesis in crib-biting and healthy controls, using a cognitive task, reversal learning, which has been used as a diagnostic for basal ganglia dysfunction. The procedure consisted of exposing subjects to four learning tasks; first and second acquisition, and their reversals. For each task, we measured the number of trials to reach criterion and heart rate and heart-rate variability. Importantly, we did not try to prevent crib-biters from executing their stereotypic behaviour. We found that the first reversal learning task required the largest number of trials, confirming its challenging nature. Interestingly, the second reversal learning task required significantly fewer trials to reach criterion, suggesting generalisation learning. However, we did not find any performance differences across groups; both stereotypic and control animals required a similar numbers of trials and did not differ in their physiological responses. Our results thus challenge the widely held belief that crib-biting horses, and stereotypic animals more generally, are cognitively impaired. We conclude that cognitive underperformance may occur in stereotypic horses if they are prevented from crib-biting to cope with experienced stress.

Persistence and resistance to extinction in the domestic dog: Basic research and applications to canine training

This review summarizes the research investigating behavioral persistence and resistance to extinction in the dog. The first part of this paper reviews Behavioral Momentum Theory and its applications to Applied Behavior Analysis and training of pet dogs with persistent behavioral problems. I also highlight how research on Behavioral Momentum Theory can be applied to the training of detection dogs in an attempt to enhance detection performance in the presence of behavioral disruptors common in operational settings. In the second part of this review, I highlight more basic research on behavioral persistence with dogs, and how breed differences and experiences with humans as alternative sources of reinforcement can influence dogs' resistance to extinction of a target behavior. Applied Behavior Analysis and Behavior Momentum Theory have important applications for behavioral treatments to reduce the persistence of problem behavior in dogs and for the development of enhanced training methods that enhance the persistence of working dogs. Dogs can also be leveraged as natural models of stereotypic behavior and for exploring individual differences in behavioral persistence by evaluating breed and environmental variables associated with differences in canine persistance.

Developing a 3-choice serial reaction time task for examining neural and cognitive function in an equine model

BACKGROUND

Large animal models of human neurological disorders are advantageous compared to rodent models due to their neuroanatomical complexity, longevity and their ability to be maintained in naturalised environments. Some large animal models spontaneously develop behaviours that closely resemble the symptoms of neural and psychiatric disorders. The horse is an example of this; the domestic form of this species consistently develops spontaneous stereotypic behaviours akin to the compulsive and impulsive behaviours observed in human neurological disorders such as Tourette's syndrome. The ability to non-invasively probe normal and abnormal equine brain function through cognitive testing may provide an extremely useful methodological tool to assess brain changes associated with certain human neurological and psychiatric conditions.

NEW METHOD

An automated operant system with the ability to present visual and auditory stimuli as well as dispense salient food reward was developed. To validate the system, ten horses were trained and tested using a standard cognitive task (three choice serial reaction time task (3-CSRTT)).

RESULTS

All animals achieved total learning criterion and performed six probe sessions. Learning criterion was met within 16.30±0.79 sessions over a three day period. During six probe sessions, level of performance was maintained at 80.67±0.57% (mean±SEM) accuracy.

COMPARISON WITH EXISTING METHOD(S)

This is the first mobile fully automated system developed to examine cognitive function in the horse.

CONCLUSIONS

A fully-automated operant system for mobile cognitive function of a large animal model has been designed and validated. Horses pose an interesting complementary model to rodents for the examination of human neurological dysfunction.

Neural modulators of temperament: A multivariate approach to personality trait identification in the horse

A relationship between dopamine and temperament has previously been described in human cases of dopaminergic dysfunction. Adjustment in temperament prior to disease manifestation can enable the early identification of individuals at risk of such conditions, and scope exists to extend this application of temperament alterations to cases of dopaminergic dysfunction in horses. A multivariate and mixed-methods approach utilising a questionnaire along with two inferred measurements of dopamine activity (Spontaneous Blink Rate [SBR] and behavioral initiation rate [BIR]) were recorded from direct observation of animals (n=99) to identify the potential relationship between dopamine and temperament in horses. Principal components analysis (PCA) of 36 temperament variables revealed nine principal components, including 'Anxiety' and 'Docility', which accounted for 72.4% of the total variance. Component scores were calculated and correlated with SBR and BIR utilising Spearman rank correlation coefficient analysis. The component 'Anxiety' was found to have a significant positive relationship with SBR, whereas 'Docility' was observed to have a significant negative relationship with SBR. These results indicate a relationship between dopamine and temperament within the horse that is certainly worthy of further study. Potential mechanisms involving neural dopaminergic and GABAergic systems are presented, in addition to how such alterations could be utilised to probe for equine dopamine dysfunction pending future research.

Effect of Cage-Induced Stereotypies on Measures of Affective State and Recurrent Perseveration in CD-1 and C57BL/6 Mice

Stereotypies are abnormal repetitive behaviour patterns that are highly prevalent in laboratory mice and are thought to reflect impaired welfare. Thus, they are associated with impaired behavioural inhibition and may also reflect negative affective states. However, in mice the relationship between stereotypies and behavioural inhibition is inconclusive, and reliable measures of affective valence are lacking. Here we used an exploration based task to assess cognitive bias as a measure of affective valence and a two-choice guessing task to assess recurrent perseveration as a measure of impaired behavioural inhibition to test mice with different forms and expression levels of stereotypic behaviour. We trained 44 CD-1 and 40 C57BL/6 female mice to discriminate between positively and negatively cued arms in a radial maze and tested their responses to previously inaccessible ambiguous arms. In CD-1 mice (i) mice with higher stereotypy levels displayed a negative cognitive bias and this was influenced by the form of stereotypy performed, (ii) negative cognitive bias was evident in back-flipping mice, and (iii) no such effect was found in mice displaying bar-mouthing or cage-top twirling. In C57BL/6 mice neither route-tracing nor bar-mouthing was associated with cognitive bias, indicating that in this strain these stereotypies may not reflect negative affective states. Conversely, while we found no relation of stereotypy to recurrent perseveration in CD-1 mice, C57BL/6 mice with higher levels of route-tracing, but not bar-mouthing, made more repetitive responses in the guessing task. Our findings confirm previous research indicating that the implications of stereotypies for animal welfare may strongly depend on the species and strain of animal as well as on the form and expression level of the stereotypy. Furthermore, they indicate that variation in stereotypic behaviour may represent an important source of variation in many animal experiments.

The disrupted basal ganglia and behavioural control: an integrative cross-domain perspective of spontaneous stereotypy

Spontaneous stereotypic behaviour (SB) is common in many captive animal species, as well as in humans with some severe psychiatric disorders, and is often cited as being related to general basal ganglia dysfunction. Despite this assertion, there is little in the literature examining SB specifically in terms of the basal ganglia mechanics. In this review, we attempt to fill this gap by offering an integrative, cross-domain perspective of SB by linking what we currently understand about the SB phenotype with the ever-growing literature on the anatomy and functionality of the basal ganglia. After outlining current models of SB from different theoretical perspectives, we offer a broad but detailed overview of normally functioning basal ganglia mechanics, and attempt to link this with current neurophysiological evidence related to spontaneous SB. Based on this we present an empirically derived theoretical framework, which proposes that SB is the result of a dysfunctional action selection system that may reflect dysregulation of excitatory (direct) and inhibitory (indirect and hyperdirect) pathways as well as alterations in mechanisms of behavioural switching. This approach also suggests behaviours that specifically become stereotypic may reflect inbuilt low selection threshold behavioural sequences associated with early development and the species-specific ethogram or, low threshold behavioural sequences that are the result of stress-induced dopamine exposure at the time of performance.

Association between increased behavioral persistence and stereotypy in the pet dog

The aim of the present study was to evaluate whether dogs that exhibit stereotypy also show higher behavioral persistence in an extinction-learning task. Thirteen pet dogs with stereotypy and 13 breed-matched control dogs were assessed on a resistance to extinction test. Each dog was trained for 40 trials using a food reinforcer to nose-touch the experimenter's hand on a continuous reinforcement schedule. After acquisition, the dogs entered an extinction phase, during which food was no longer delivered. The numbers of nose-touches as well as inter-response times during this phase were recorded. A linear regression found that stereotypy status (t=-2.46, P=.027) and breed type (t=2.44, P=.023) were significant predictors of the number of responses in extinction. Dogs with stereotypy responded more in extinction than control dogs. The mean number of responses was 13.4 (SD=14.7) in the control group and 26.0 (SD=15.3) in the stereotypy group. These results suggest a link between previous laboratory and zoo animal findings on the neurophysiology of stereotypy and the pet dog population. They also have implications for the use of extinction procedures to reduce stereotypic behaviors in pet dogs, as these dogs show enhanced resistance to extinction.

Exploration of known stereotypic behaviour-related candidate genes in equine crib-biting

Crib-biting in horses is a stereotypic oral behaviour. Genetic susceptibility has been suggested on a causal basis, together with environmental factors such as stress, gastric discomfort and frustration caused by stall restrictions. This study aimed to test the associations of known or suspected stereotypic genes with equine crib-biting, including Ghrelin, Ghrelin receptor, Leptin, Dopamine receptor, μ-opioid receptor, N-cadherin, Serotonin receptor and Semaphorin. We conducted a candidate gene study with a case-control design, including 98 crib-biting and 135 control horses of two breeds, Finnhorses and half-breds. Detailed phenotypic information on crib-biting behaviour was surveyed through an owner-completed questionnaire. Control horses were more than 10 years old and without a history of crib-biting. Single nucleotide polymorphisms flanking the candidate genes were genotyped using either Sanger sequencing or Taqman assays. According to the survey, the affected horses started crib-biting at a young age, had exhibited crib-biting for more than a year, and expressed the behaviour after feeding or when stressed. Comparison of allele frequencies between the cases and controls for each breed separately did not provide evidence of an association at any of the tested loci. These results suggest that the previously known stereotypic genes are not major risk factors for crib-biting in horses, and further genome-wide studies are warranted on larger sample cohorts.

Environmentally enriched rearing environments reduce repetitive perseveration in caged mink, but increase spontaneous alternation

Studies spanning 15 species (including American mink, Neovison vison) demonstrate that within similarly-housed populations, individuals displaying high levels of stereotypic behaviour (SB) typically show perseverative responding (e.g. during set-shifting, or reversal/extinction learning). Similar correlations in autism and schizophrenia suggest this indicates captivity-induced cortico-striatal circuit dysfunction. However, this pattern does not prove developmental impairment: SB, perseveration and their inter-correlations also occur in normal humans. We therefore differentially-reared enriched versus non-enriched mink to investigate whether treatments that exacerbate SB correspondingly increase perseveration (Study 1). Enriched-rearing did reduce SB and perseverative response repetition (in two-choice guessing tasks), while increasing spontaneous alternation: a strategy yielding more rewards, and suggesting enhanced hippocampal development. This complements previous research demonstrating cortical/hippocampal impairments and reduced behavioural flexibility in non-enriched animals, with implications for research animals and wild animals captive-raised for reintroduction into nature. Consistent with previous data, highly stereotypic subjects repeated guessing task responses most rapidly, suggesting disinhibition during repetition. However, unexpectedly, SB and perseveration did not co-vary across individuals. We therefore suggest that behavioural changes manifest as increased perseveration are important but do not fully explain captive animals' SBs, possible reasons including the contributory role of differential motivations for underlying source behaviours. Re-analyses of old data (Study 2) confirmed that spontaneous alternation is profitable; and demonstrated that the precise methods used for quantifying perseveration and SB can modify the strength of apparent relationships between them, as can statistically controlling for feeding motivation: as predicted, partialling out motivational effects increased the variance in SB predicted by perseveration.

Recurrent perseveration correlates with abnormal repetitive locomotion in adult mink but is not reduced by environmental enrichment

We analysed the relationship between abnormal repetitive behaviour (ARB), the presence/absence of environmental enrichment, and two types of behavioural disinhibition in farmed American mink, Neovison vison. The first type, recurrent perseveration, the inappropriate repetition of already completed responses, was assessed using three indices of excessive response repetition and patterning in a bias-corrected serial two-choice guessing task. The second type, disinhibition of prepotent responses to reward cues, a form of impulsivity, was tested in a locomotive detour task adapted from primate reaching tasks: subjects were required to walk around, rather than directly into, a transparent barrier behind which food was visible. In older adult females, recurrent perseveration positively predicted pre-feeding abnormal repetitive locomotion (ARL) in Non-enriched housing. High-ARL subjects also performed repeated (same-choice) responses more rapidly than low-ARL animals, even when statistically controlling for alternated (different-choice) response latency. Mink performed much less ARL following transfer to Enriched housing, but there was no corresponding change in recurrent perseveration. Thus, elevated recurrent perseveration is not sufficient for frequent ARL; and while captive environments do determine ARL frequency, in mink, they do not necessarily do so by modifying levels of perseveration. Disinhibition of prepotent responses to reward cues, meanwhile, did not predict ARL. In a separate sample of differentially housed young adults, neither type of behavioural disinhibition predicted ARL, and again, whether or not housing was enriched did not affect behavioural disinhibition despite affecting ARL. Thus, the relationship between recurrent perseveration and ARB may only develop with age; longitudinal studies are now required for confirmation.

Differential place and response learning in horses displaying an oral stereotypy

Significant similarities exist between the neural and behavioural features of environmentally and drug-induced stereotypy. For example, exposure to dopamine agonists, such as amphetamine, induces stereotypy and causes alterations in midbrain neurophysiology similar to those observed following chronic stress. An additional behavioural feature of these neural changes in the drug-induced phenotype is an enhanced rate of switching from response-outcome (R-O) to stimulus-response (S-R) learning. The aim of the current experiment was to examine R-O and S-R learning in horses displaying environmentally induced oral stereotypies. This was achieved by employing variations of the place/response paradigm. In Experiment 1, we found that crib-biting horses displayed 'response' learning after 20 learning trials, whereas non-crib-biting controls tended to display 'place' learning throughout the experiment. In Experiment 2, we used a modified version of the procedure, in which the subjects were introduced to the maze from different start points and forced always to turn the same way. We found that the crib-biters acquired the task at a faster rate suggesting again that this group was displaying 'response' learning. Finally, in Experiment 3, we carried out an arena test to ensure that crib-biters were capable of 'place' learning. These results are the first to show that horses displaying an oral stereotypy, a behavioural phenotype previously associated with stress-induced perturbations of the basal ganglia, preferentially use 'response' learning. The findings are discussed in relation to the search for an aetiological model of stereotypy.

Effect of an open window and conspecifics within view on the welfare of stabled horses, estimated on the basis of positive and negative behavioural indicators

The effect of environmental enrichment on the welfare of stabled horses was estimated on the basis of positive and negative behavioural indicators. Six stabled horses were exposed for seven days to each of two conditions in early spring: i) a window at the back of the loose box was opened, but no horses were within the view of the subject horses (OW) and ii) the window in the loose box was opened and two horses that had been in the same stable as the subject horses were turned out to the paddock next to the stable and were within view of the subject horses (OWH). The window in the loose box had been closed prior to the start of the study for protection against the cold during winter months (CW condition) but horses could see outside the loose box through the grille door. The behaviour of the subject horses was recorded by video camera from 1300 to 1530h, firstly, in the CW condition for the three days prior to treatment as the control condition, and then for the last three days of each week in the OW and OWH conditions. The behaviour was focal- and instantaneous-sampled at 30-s intervals. Significant differences between the effects of the loose box conditions on the mean percentage of time spent in standing behaviour, looking behaviour, and bedding investigation behaviour (which may be an indicator of frustration) were observed but no significant difference in the mean percentage of time spent in standing-sleep behaviour (which may be an indicator of behavioural satisfaction) was observed. When the window was opened, bedding investigation and standing behaviour decreased and, when the conspecifics were within view, bedding investigation behaviour decreased and looking behaviour increased. The results suggested that the OW and OWH treatments suppressed the frustration of stabled horses which did not perform any abnormal behaviour, but may not increase the behavioural satisfaction of stabled horses.

Mule cognition: a case of hybrid vigour?

This study compares the behaviour of the mule (Equus asinus x Equus caballus) with that of its parent species to assess the effects of hybridization on cognition. Six mules, six ponies (E. caballus) and six donkeys (E. asinus) were given a two choice visual discrimination learning task. Each session consisted of 12 trials and pass level was reached when subjects chose the correct stimulus for at least 9 out of the 12 trials in three consecutive sessions. A record was made of how many pairs each subject learnt over 25 sessions. The mules' performance was significantly better than that of either of the parent species (Kruskal-Wallis: H(x) = 8.11, P = 0.017). They were also the only group to learn enough pairs to be able to show a successive reduction in the number of sessions required to reach criterion level. This study provides the first empirical evidence that the improved characteristics of mules may be extended from physical attributes to cognitive function.

Impaired instrumental choice in crib-biting horses (Equus caballus)

Horses displaying an oral stereotypy were tested on an instrumental choice paradigm to examine differences in learning from non-stereotypic counterparts. Stereotypic horses are known to have dysfunction of the dorsomedial striatum, and lesion studies have shown that this region may mediate response-outcome learning. The paradigm was specifically applied in order to examine learning that requires maintenance of response-outcome judgements. The non-stereotypic horses learned, over three sessions, to choose a more immediate reinforcer, whereas the stereotypic horses failed to do so. This suggests an initial behavioural correlate for dorsomedial striatum dysregulation in the stereotypy phenotype.