According to the study presented in 2009 during the meeting of the American Psychological Association, dogs may be as smart as two-year-old children. On top of the most intelligent dogs is  a border collie. Some representatives of this breed are able to understand even 200 words.

Poodles, German shepherds, golden retrievers and dobermans also belong to the top five, whereas a  the most popular breed in America – labrador retriever, is on the 7^th place. As scientists point out, older dog breeds, such as hounds, bulldog or beagle, belong to a group of dogs that need more time to learn. Contrary to younger breeds, the task of which is to assisst humans, older breeds were bred to sniff and hunt, thus what was more important was their physical strength rather that cleverness.

Source: www.livescience.com