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Krueger, K., & Farmer, K. (2011). Laterality in the Horse [Lateralität beim Pferd ]. mup, 4, 160–167.
Abstract: Horses are one-sided, not only on a motor level, but they also prefer to use one eye, ear or nostril over the other under particular circumstances. Horses usually prefer using the left eye to observe novel objects and humans. This preference is more marked in emotional situations and when confronted with unknown persons. Thus the horse’s visual laterality provides a good option for assessing its mental state during training or in human-horse interactions. A strong preference for the left eye may signal that a horse cannot deal with certain training situations or is emotionally affected by a particular person.
Pferde benutzen für die Begutachtung von Objekten und Menschen bevorzugt eine bestimmte Nüster, ein Ohr oder ein Auge. So betrachten die meisten Pferde Objekte und Menschen mit dem linken Auge. Die Lateralitätsforschung erklärt diese sensorische Lateralität mit der Verarbeitung von Informationen unterschiedlicher Qualität in verschiedenen Gehirnhälften und zeigt auf, dass positive und negative emotionale Informationen sowie soziale Sachverhalte mit dem linken Auge aufgenommen und vorwiegend an die rechte Gehirnhälfte weitergegeben werden. In diesem Zusammenhang ermöglicht die visuelle Lateralität, den Gemütszustand des Pferdes im Training und im therapeutischen Fördereinsatz zu erkennen und zu berücksichtigen. |
Krueger, K., Schwarz, S., Marr, I., & Farmer, K. (2022). Laterality in Horse Training: Psychological and Physical Balance and Coordination and Strength Rather Than Straightness. Animals, 12(8), 1042.
Abstract: For centuries, a goal of training in many equestrian disciplines has been to straighten the horse, which is considered a key element in achieving its responsiveness and suppleness. However, laterality is a naturally occurring phenomenon in horses and encompasses body asymmetry, motor laterality and sensory laterality. Furthermore, forcibly counterbalancing motor laterality has been considered a cause of psychological imbalance in humans. Perhaps asymmetry and laterality should rather be accepted, with a focus on training psychological and physical balance, coordination and equal strength on both sides instead of enforcing “straightness”. To explore this, we conducted a review of the literature on the function and causes of motor and sensory laterality in horses, especially in horses when trained on the ground or under a rider. The literature reveals that body asymmetry is innate but does not prevent the horse from performing at a high level under a rider. Motor laterality is equally distributed in feral horses, while in domestic horses, age, breed, training and carrying a rider may cause left leg preferences. Most horses initially observe novel persons and potentially threatening objects or situations with their left sensory organs. Pronounced preferences for the use of left sensory organs or limbs indicate that the horse is experiencing increased emotionality or stress, and long-term insufficiencies in welfare, housing or training may result in left shifts in motor and sensory laterality and pessimistic mentalities. Therefore, increasing laterality can be regarded as an indicator for insufficiencies in housing, handling and training. We propose that laterality be recognized as a welfare indicator and that straightening the horse should be achieved by conducting training focused on balance, coordination and equal strength on both sides.
Keywords: balance; body asymmetry; equitation; horse; motor laterality; sensory laterality; stress; welfare
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Larose, C., Richard-Yris, M. - A., Hausberger, M., & Rogers, L. J. (2006). Laterality of horses associated with emotionality in novel situations. Laterality, 11(4), 355–367.
Abstract: We have established that lateral biases are characteristic of visual behaviour in 65 horses. Two breeds, Trotters and French Saddlebreds aged 2 to 3, were tested on a novel object test. The main finding was a significant correlation between emotionality index and the eye preferred to view the novel stimulus: the higher the emotionality, the more likely that the horse looked with its left eye. The less emotive French Saddlebreds, however, tended to glance at the object using the right eye, a tendency that was not found in the Trotters, although the emotive index was the same for both breeds. The youngest French Saddlebreds did not show this trend. These results are discussed in relation to the different training practices for the breeds and broader findings on lateralisation in different species.
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Leighty, K. A., & Fragaszy, D. M. (2003). Joystick acquisition in tufted capuchins (Cebus apella). Anim. Cogn., 6(3), 141–148.
Abstract: A number of nonhuman primate species have demonstrated the ability to use a joystick to control a cursor on a computer screen, yet the acquisition of this skill has not been the focus of systematic inquiry. Here, we examined joystick acquisition in four tufted capuchins under two directional relationships of joystick movement and resultant cursor displacement, isomorphic and inverted. To document the natural history of the acquisition of this skill, we recorded the development of visual tracking of the cursor and body tilting. Rates of acquisition were comparable between the two conditions. After mastering the task in one condition, subjects remastered the task at an accelerated rate in the opposing condition. All subjects significantly increased or maintained high proportions of cursor tracking throughout acquisition. All subjects demonstrated a postural tilt while moving the cursor from the mid-phase of acquisition through task mastery. In the isomorphic condition, all subjects tilted significantly more often in the direction of goal location than in the opposite direction. In three of the four series of tilting that were scored for subjects in the inverted condition, tilting occurred significantly more often toward the direction of goal location than the direction of required hand movement. Together these findings suggest that body tilting participates in the organization of directional movement of the cursor rather than reflecting merely the motoric requirements of the task (to manipulate a joystick).
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Lucidi, P., Bacco, G., Sticco, M., Mazzoleni, G., Benvenuti, M., Bernabò, N., et al. (2013). Assessment of motor laterality in foals and young horses (Equus caballus) through an analysis of derailment at trot. Physiol. Behav., 109, 8–13.
Abstract: The conflicting results regarding the study of motor laterality in horses may indicate that there does not exist a proper method to assess the degree and the direction of motor bias in these animals. Unfortunately, even less is known about the development of laterality in horses, and to what extent early manipulations can still exert their effects in adulthood. We propose a new method that can be easily applied at a very early age thus avoiding testing adult horses eventually biased by human handling and/or training. Forty-six horses (29 nine-month-old foals and 17 two-year old horses) were handled since birth bilaterally and housed in groups in wide areas. At the time of the analysis, in order to minimize environmental and sensorial disturbances, each horse was tested in a round pen individually or as dyad mother-foal. The ability/inability to properly execute a circle at trot was then recorded, assuming the direction of derailment, i.e. the cutting of the circle, as an indicator of motor bias. From the results of the study it is arguable that motor laterality in horses is acquired over time: in fact foals tested while their mothers were being subjected to longeing showed a higher percentage of ambidextrous animals, while two-year-old horses appeared biased toward the right (p<0.05). Results are discussed in the light of the scientific knowledge about equine biomechanics, taking into account horses' locomotion that leads to the advancement of the body mass through the activation of a kinetic chain that originates from the hindquarters.
Keywords: Horse; Laterality; Longeing; Sidedness
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McGreevy, P. D., & Thomson, P. C. (2006). Differences in motor laterality between breeds of performance horse. Appl. Anim. Behav. Sci., 99(1-2), 183–190.
Abstract: This study examined the relationship between motor laterality in horses bred for different types of work and therefore different temperaments. Foreleg preference during grazing was measured in three populations of domestic horse, Thoroughbreds (TB, bred to race at the gallop), Standardbreds (SB, bred for pacing) and Quarter Horses (QH, in this case bred for so-called “cutting work” which involves manoeuvring individual cattle in and out of herds). With a one-sample t-test, TBs showed strong evidence of a left preference in motor laterality (P = 0.000), as did SBs (P = 0.002) but there was no convincing evidence for laterality in QH (P = 0.117). However, the increasing trend in left preference from QH to SBs then TBs was associated with increasing differences between individual horses within a breed. The overall preference (either left or right) increased with age (P = 0.008) and the rate of increase varied with breeds. The presence of a higher proportion of left-foreleg preferent individuals in TBs and SBs compared with QH may indicate that their training or selection (or both) has an effect on motor bias.
Keywords: Horse; Lateralisation; Laterality; Breed; Training
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Murphy, J., Sutherland, A., & Arkins, S. (2005). Idiosyncratic motor laterality in the horse. Appl. Anim. Behav. Sci., 91(3-4), 297–310.
Abstract: Idiosyncratic motor behaviour was investigated during four experimental procedures in 40 horses (males = 20, females = 20) to establish if horses revealed evidence of significant right or left laterality. The experimental procedures included (1) detection of the preferred foreleg to initiate movement (walk or trot), (2) obstacle avoidance within a passageway (right or left), (3) obstacle avoidance when ridden and (4) idiosyncratic motor bias when rolling. The influence of the horses' sex on both the direction and the degree of the laterality was explored within and between experimental procedures. The findings showed that the direction, but not the degree of idiosyncratic motor preference in the horses was strongly sex-related. Male horses exhibited significantly more (t = 3.74, d.f. = 79, P < 0.001) left lateralised responses and female horses exhibited significantly more (t = -6.35, d.f. = 79, P < 0.01) right lateralised responses. There was also significant positive correlation (P < 0.05) between four of six possible inter-experimental relationships. The results suggest two discrete trends of laterality associated with the sex of the horse. The primary cause of idiosyncratic motor laterality may be genetically predetermined, influenced by environmental factors or a combination of these two and the current findings may support the development of sex-specific training schedules for the horse. Further, work in this area might assist in defining the mechanisms of brain hemisphere lateralisation and allocation of cognitive function in the horse.
Keywords: Horse; Idiosyncratic motor behaviour; Laterality; Sidedness
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Parr, L. A., Hopkins, W. D., & de Waal, F. B. (1997). Haptic discrimination in capuchin monkeys (Cebus apella): evidence of manual specialization. Neuropsychologia, 35(2), 143–152.
Abstract: Two experiments investigated the effects of haptic and visual discrimination on hand preference in 22 brown capuchin monkeys (Cebus apella). The percentage of left-handed subjects in Experiment 1 were 63.6%, 45.5%, and 18.2% for haptic, bipedal, and quadrupedal reaching, respectively. In Experiment 2, the haptic demands of the task were manipulated by using additional food types and another tactile medium. Left-hand preferences were further strengthened when reaching into water compared to pineshavings in Experiment 1. Reaching with no tactile interference resulted in equal numbers of lateralized and nonlateralized subjects. These results show that when reaching demands the use of haptic cues, as opposed to visual ones, monkeys shift towards greater left hand use. This is consistent with what is known about right hemisphere superiority for haptic discrimination in humans.
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Pell, M. D. (2006). Cerebral mechanisms for understanding emotional prosody in speech. Brain and Language, 96(2), 221–234.
Abstract: Hemispheric contributions to the processing of emotional speech prosody were investigated by comparing adults with a focal lesion involving the right (n = 9) or left (n = 11) hemisphere and adults without brain damage (n = 12). Participants listened to semantically anomalous utterances in three conditions (discrimination, identification, and rating) which assessed their recognition of five prosodic emotions under the influence of different task- and response-selection demands. Findings revealed that right- and left-hemispheric lesions were associated with impaired comprehension of prosody, although possibly for distinct reasons: right-hemisphere compromise produced a more pervasive insensitivity to emotive features of prosodic stimuli, whereas left-hemisphere damage yielded greater difficulties interpreting prosodic representations as a code embedded with language content.
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Rogers, L. J. (2000). Evolution of hemispheric specialization: advantages and disadvantages. Brain Lang, 73(2), 236–253.
Abstract: Lateralization of the brain appeared early in evolution and many of its features appear to have been retained, possibly even in humans. We now have a considerable amount of information on the different forms of lateralization in a number of species, and the commonalities of these are discussed, but there has been relatively little investigation of the advantages of being lateralized. This article reports new findings on the differences between lateralized and nonlateralized chicks. The lateralized chicks were exposed to light for 24 h on day 19 of incubation, a treatment known to lead to lateralization of a number of visually guided responses, and the nonlateralized chicks were incubated in the dark. When they were feeding, the lateralized chicks were found to detect a stimulus resembling a raptor with shorter latency than nonlateralized chicks. This difference was not a nonspecific effect caused by the light-exposed chicks being more distressed by the stimulus. Instead, it appears to be a genuine advantage conferred by having a lateralized brain. It is suggested that having a lateralized brain allows dual attention to the tasks of feeding (right eye and left hemisphere) and vigilance for predators (left eye and right hemisphere). Nonlateralized chicks appear to perform these dual tasks less efficiently than lateralized ones. Reference is made to other species in discussing these results.
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