Despite having a comparable brain size to other highly evolved animals, sheep have been historically perceived as unintelligent and were therefore not considered to be good animal models for studying diseases that affect learning and memory. However, new research recently published in the journal PLoS ONE shows that sheep are indeed smarter than previously believed. The researchers are hopeful the animals will prove useful for research into diseases that impair the cognitive abilities of patients, such as Huntington’s disease (HD) and Alzheimer’s disease. Sheep are quadrupedal, ruminant mammals typically kept as livestock. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Although the name “sheep” applies to many species in the genus Ovis, in everyday usage it almost always refers to Ovis aries. Numbering a little over one billion, domestic sheep are also the most numerous species of sheep.