Dog

The existence and nature of personality traits in dogs have been studied (15329 dogs of 164 different breeds) and five consistent and stable "narrow traits" identified, described as playfulness, curiosity/fearlessness, chase-proneness, sociability and aggressiveness. A further higher order axis for shyness–boldness was also identified.
Dog growl
A new study in Budapest, Hungary has found that dogs are able to tell how big another dog is just by listening to its growl. A specific growl used by dogs to protect their food. The research also shows that dogs do not lie about their size, and this is the first time research has shown animals can determine another’s size by the sound it makes. The test used image of many kind of dogs and together showed a small and big dog and also a growl. The result, showed that 20 of the 24 test dogs looked at the image of the appropriate-sized dog first and looked at it longest.