Abstract: From the viewpoint of experimental psychology, there are two problems with our current knowledge of equine perception. The first is that the behavioral and neurophysiological research in this area has enormous gaps, reflecting that this animal is not a convenient laboratory subject. The second is that the horse, having been a close companion to humans for many millennia, entrenched anecdotal wisdom is often hard to separate from scientific fact. Therefore, any summary at present of equine perception has to be provisional. The horse appears to have developed a visual system particularly sensitive to dim light and movement, it may or may not have a weak form of color vision in part of the retina, it has little binocular overlap, and its best acuity is limited to a restricted horizontal band which is aimed primarily by head/neck movements. However, the total field of view is very large. Overall, as would be expected for a prey animal, horse vision appears to have evolved more for detection of predator approach from any angle than for accurate visual identification of stationary objects, especially those seen at a distance. It is likely that, as for most mammals except the primates, horses rely more heavily on their other senses for forming a view of their world. Equine high-frequency hearing extends far above that of humans, but horses may be less able to localize the point of origin of brief sounds. The horse's capacity for chemoreception and its reliance on chemical information for identification may more closely resemble that of the dog than of the human. Its tactile sensitivity is high, and the ability of its brain and body to regulate pain perception appears to be similar to that found in other mammals. There is room for a great deal of future research in both the area of equine perception and sensory-based cognition, but for the present time persons interacting with this animal should be made aware of the importance of the sounds they make, the movements of their bodies, the way they touch the animal, and the odors they emit or carry on their clothing.

Abstract: Horses are well able to form classical and instrumental associations and so the focus of much recent research has been on the stimulus control of instrumental learning. Horses appear to discriminate using spatial cues more easily than other stimulus features, as indicated both by the speed of initial task acquisition and by the extent to which acquired discriminations can be reversed. Phenomena associated with discrimination learning in laboratory animals, including generalisation and peak shift, have been demonstrated in horses. However, the ability of horses to classify stimuli into categories is more controversial. Although there is some evidence that horses may be able to form categories based on similarities in the physical appearance of different stimuli, there is currently no evidence that they are able to develop abstract concepts. Their performance on social learning tasks has also been poor. Few correlations are observed between the learning ability of individual horses on different tasks, suggesting that it may not be possible to classify individual horses as `good' or `poor' learners. Better learning performance by horses that are naturally calm is probably due to reduced interference in the learning process. Correct handling procedures can lower reactivity levels in horses, and may facilitate learning in some circumstances. Future research on equine learning needs to take into account the complex nature of equine social interaction. Studies on the effects of stress on learning, and on social and spatial cognition, are also particularly needed.

Abstract: Considered an indicator of self-awareness, mirror self-recognition (MSR) has long seemed limited to humans and apes. In both phylogeny and human ontogeny, MSR is thought to correlate with higher forms of empathy and altruistic behavior. Apart from humans and apes, dolphins and elephants are also known for such capacities. After the recent discovery of MSR in dolphins (Tursiops truncatus), elephants thus were the next logical candidate species. We exposed three Asian elephants (Elephas maximus) to a large mirror to investigate their responses. Animals that possess MSR typically progress through four stages of behavior when facing a mirror: (i) social responses, (ii) physical inspection (e.g., looking behind the mirror), (iii) repetitive mirror-testing behavior, and (iv) realization of seeing themselves. Visible marks and invisible sham-marks were applied to the elephants' heads to test whether they would pass the litmus “mark test” for MSR in which an individual spontaneously uses a mirror to touch an otherwise imperceptible mark on its own body. Here, we report a successful MSR elephant study and report striking parallels in the progression of responses to mirrors among apes, dolphins, and elephants. These parallels suggest convergent cognitive evolution most likely related to complex sociality and cooperation.

Abstract: Linear hierarchies, the classical pecking-order structures, are formed readily in both nature and the laboratory in a great range of species including humans. However, the probability of getting linear structures by chance alone is quite low. In this paper we investigate the two hypotheses that are proposed most often to explain linear hierarchies: they are predetermined by differences in the attributes of animals, or they are produced by the dynamics of social interaction, i.e., they are self-organizing. We evaluate these hypotheses using cichlid fish as model animals, and although differences in attributes play a significant part, we find that social interaction is necessary for high proportions of groups with linear hierarchies. Our results suggest that dominance hierarchy formation is a much richer and more complex phenomenon than previously thought, and we explore the implications of these results for evolutionary biology, the social sciences, and the use of animal models in understanding human social organization.