Löckener, S., Reese, S., Erhard, M., & Wöhr, A. - C. (2016). Pasturing in herds after housing in horseboxes induces a positive cognitive bias in horses. Journal of Veterinary Behavior: Clinical Applications and Research, 11, 50–55.
Abstract: Abstract Horses are kept in various housing systems, for example, with conspecifics in horse pens or singly in horseboxes, with or without pasturing. To provide appropriate living conditions for horses, it is necessary to know in which conditions they feel well or unwell. Here, a cognitive bias assessment provides information about an individual's affective state and its well-being. When a positive affective state prevails, animals tend to judge optimistically in ambiguous situations. When a negative affective state prevails, animals judge pessimistically in unclear situations. In the present study, we trained horses on a spatial discrimination task and evaluated their judgment of ambiguous locations when they had access to pastures and contact to conspecifics versus when they were kept singly in horseboxes. Ten days of pasturing and contact with conspecifics after being kept singly in horseboxes for 6 months induced a positive cognitive bias in the horses. We suggest that horses need to act out certain behaviors like exploration, social interaction, play, or grooming to fulfill their needs. After a time in which they were individually in horseboxes without pasturing and access to the herd, they seem to have a positive cognitive bias once they have access to pastures and conspecifics. This positive cognitive bias effect seems to disappear over time, as horses appear to adapt to the circumstances.
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Péron, F., Ward, R., & Burman, O. (2013). Horses (Equus caballus) discriminate body odour cues from conspecifics. Animal Cognition, , 1–5.
Abstract: Knowledge about social recognition and memory in animals can help us to determine appropriate management and husbandry techniques. In this study, we used a habituation–discrimination procedure to investigate the ability of horses (Equus caballus) to distinguish between the body odour samples of unfamiliar conspecifics. To pick up body odour, we rubbed material on the coat of horses and presented these unknown body odours to 16 different conspecifics of the same sex and similar age. The test consisted of two successive two-min presentations of a sample from one individual (e.g. individual ‘A’) and a simultaneous presentation of samples from individual ‘A’ and a novel individual (e.g. individual ‘B’) during a final third presentation. The results showed that horses, regardless of sex, decreased the time they spent investigating conspecific body odour across the initial two presentations—demonstrating habituation. In the final presentation, the results demonstrated successful discrimination of the previously experienced odour because horses investigated the novel olfactory sample (‘B’) significantly more than the pre-exposed sample (‘A’). Taken together, these findings suggest, for the first time, that horses are able to discriminate two stimuli derived from body odours of unfamiliar conspecifics over short period of time.
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Lampe, J. F., & Andre, J. (2012). Cross-modal recognition of human individuals in domestic horses (Equus caballus). Animal Cognition, 15(4), 623–630.
Abstract: This study has shown that domestic horses are capable of cross-modal recognition of familiar humans. It was demonstrated that horses are able to discriminate between the voices of a familiar and an unfamiliar human without seeing or smelling them at the same moment. Conversely, they were able to discriminate the same persons when only exposed to their visual and olfactory cues, without being stimulated by their voices. A cross-modal expectancy violation setup was employed; subjects were exposed both to trials with incongruent auditory and visual/olfactory identity cues and trials with congruent cues. It was found that subjects responded more quickly, longer and more often in incongruent trials, exhibiting heightened interest in unmatched cues of identity. This suggests that the equine brain is able to integrate multisensory identity cues from a familiar human into a person representation that allows the brain, when deprived of one or two senses, to maintain recognition of this person.
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Hanggi, E. B., & Ingersoll, J. F. (2012). Lateral vision in horses: A behavioral investigation. Behav. Process., 91(1), 70–76.
Abstract: This study investigated lateral vision in horses (Equus caballus) for the first time from a behavioral point of view. Three horses were tested using a novel experimental design to determine the range of their lateral and caudolateral vision with respect to stimulus detection and discrimination. Real-life stimuli were presented along a curvilinear wall in one of four different positions (A, B, C, D) and one of two height locations (Top, Bottom) on both sides of the horse. To test for stimulus detection, the correct stimulus was paired against a control; for stimulus discrimination, the correct stimulus was paired against another object. To indicate that the correct stimulus was detected or discriminated, the horses pushed one of two paddles. All horses scored significantly above chance on stimulus detection trials regardless of stimulus position or location. They also accurately discriminated between stimuli when objects appeared in positions A, B, and C for the top or bottom locations; however, they failed to discriminate these stimuli at position D. This study supports physiological descriptions of the equine eye and provides new behavioral data showing that horses can detect the appearance of objects within an almost fully encompassing circle and are able to identify objects within most but not all of their panoramic field of view.
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Güntürkün, O., & Kesch, S. (1987). Visual lateralization during feeding in pigeons. Behav. Neurosci., 101(3), 433–435.
Abstract: In a quasi-natural feeding situation, adult pigeons had to detect and consume 30 food grains out of about 1,000 pebbles of similar shape, size, and color within 30 s under monocular conditions. With the right eye seeing, the animals achieved a significantly higher discrimination accuracy and, consequently, a significantly higher proportion of grains grasped than with the left eye seeing. This result supports previous demonstrations of a left-hemisphere dominance for visually guided behavior in birds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)
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