How Smart are Dogs?
The ability of a dog to learn quickly might be taken as a sign of intelligence, but learning speed can be affected by the rewards given in training or the motivation or activity level of the dog. For example, some breeds, such as the Siberian Huskies, are said to be not particularly interested in pleasing their owners, but quickly learn to escape from yards or catch small animals, often using ingenious methods. Various studies have attempted to estimate intelligence by measuring the number of words or signs a dog can learn.
An example reports that Rico, a Border Collie, could learn over 200 words. Rico could remember the names of several items for up to four weeks after its last exposure. Rico was also able to interpret phrases such as "fetch the sock" in terms of its component words (rather than considering the phrase to be a single word). Rico could also give the sock to a specified person. In 2008, Betsy, also a Border Collie, was featured on the cover of National Geographic Magazine. Betsy's intelligence rivaled that of Rico's in that she knew over 340 words and was able to connect an object with a photographic image of the object, despite having seen neither before.
Note: This article excerpts material from the Wikipedia article "Dog intelligence"