Nobody would dispute that cats and dogs are the two most popular species of companion animals for humans. It is no wonder that dogs are often considered to be the best friends and adopted family members of human beings: They developed the high social ability to communicate with humans during the two species' long history of co-habitation. However, it seems strange that cats are in the same position as dogs in human society, because they are more individual and less social than dogs. This review first presents the history of cat domestication. Next, it discusses the reasons why cats are now human companion animals despite such a history. This paper will discuss the cognitive and behavioral characteristics in cats that promote human-cat interaction and the similarities between cats and humans. Finally, it will discuss the significance of the study of cats' sociality.