Department of Veterinary Sciences, University of Messina, Messina, Italy.
Department of Veterinary Sciences, University of Pisa, Pisa, Italy.
PLoS One. 2021 Feb 19;16(2):e0247310. doi: 10.1371/journal.pone.0247310. eCollection 2021.
In social animals, recognizing conspecifics and distinguishing them from other animal species is certainly important. We hypothesize, as demonstrated in other species of ungulates, that horses are able to discriminate between the faces of conspecifics and the faces of other domestic species (cattle, sheep, donkeys and pigs). Our hypothesis was tested by studying inter-and intra-specific visual discrimination abilities in horses through a two-way instrumental conditioning task (discrimination and reversal learning), using two-dimensional images of faces as discriminative stimuli and food as a positive reward. Our results indicate that 8 out of 10 horses were able to distinguish between two-dimensional images of the faces of horses and images showing the faces of other species. A similar performance was obtained in the reversal task. The horses' ability to learn by discrimination is therefore comparable to other ungulates. Horses also showed the ability to learn a reversal task. However, these results were obtained regardless of the images the tested horses were exposed to. We therefore conclude that horses can discriminate between two dimensional images of conspecifics and two dimensional images of different species, however in our study, they were not able to make further subcategories within each of the two categories. Despite the fact that two dimensional images of animals could be treated differently from two dimensional images of non-social stimuli, our results beg the question as to whether a two-dimensional image can replace the real animal in cognitive tests.
在社交动物中，识别同种动物并将其与其他动物物种区分开来无疑是很重要的。我们假设，正如在其他有蹄类动物中所证明的那样，马能够区分同种动物的面部和其他家养物种（牛、羊、驴和猪）的面部。我们通过使用二维面部图像作为辨别刺激物和食物作为正奖励的双向仪器调节任务（辨别和反转学习），研究了马的种间和种内视觉辨别能力，从而验证了我们的假设。我们的结果表明，10 匹马中有 8 匹能够区分马的二维面部图像和其他物种的面部图像。在反转任务中也获得了类似的表现。因此，马通过辨别进行学习的能力与其他有蹄类动物相当。马还表现出学习反转任务的能力。然而，无论测试的马看到什么图像，都能得到这些结果。因此，我们得出结论，马可以区分同种动物的二维图像和不同物种的二维图像，但是在我们的研究中，它们无法在每种类别中进一步进行子分类。尽管动物的二维图像可以与非社交刺激的二维图像不同对待，但我们的结果引发了一个问题，即二维图像是否可以在认知测试中替代真实动物。
