They [Scientists] have compiled a list of the most intelligent and least intelligent breeds using information from obedience classes. Border collies and retrievers were rated among the most intelligent while hounds and terriers were the least bright.

“The average dog is about as bright linguistically as a human two-year-old,” said Professor Stanley Coren, a leading expert on canine intelligence at the University of British Columbia in Vancouver who has carried out the work.”This means they can understand about 165 words, signs and signals. Those in the top 20 per cent were able to understand as many as 250 words and signals, which is about the same as a two and a half year old.

“Obviously we are not going to be able to sit down and have a conversation with a dog, but like a two-year-old, they show that they can understand words and gestures.”

Professor Coren, who presented his work on Saturday at the Annual Convention of the American Psychological Association, believes dogs are among the most intelligent animals and can rival apes and parrots for their ability to understand language.

While most dogs understand simple commands such as sit, fetch and stay, a border collie tested by Professor Coren showed a knowledge of 200 spoken words. The collie was able to recognise the names of items it was asked to fetch and correctly retrieve them.

The dog was also quick to learn the names for new items and after being taught a new word, brought back the correct item 70 per cent of the time. Other dogs have shown similar abilities, although often with fewer words but with gestures instead.Professor Coren has also found that dogs can count using established tests developed for young children. When something unexpected happens with an object, children and dogs will stare at it for a longer period of time.

By lowering a dog treat behind a screen and then another, the dog would expect to see two dog treats, but if a treat is secretly removed or another one added, the researchers found dogs would stare for longer at the treats when the screen was removed.

Professor Coren said: “Dogs can tell that one plus one should equal two and not one or three.

via Dogs as intelligent as two-year-old children – Telegraph.