Animal intelligence and its possible relationship to human intelligence is indeed a subject of great importance. In 2004 it was reported that a border collie dog (named Rico) could learn up to 200 words and could also learn some of them remembering meanings after just one single presentation (“fast mapping”), an ability described in human children. The present work aimed at re-evaluating these striking results in a female Yorkshire terrier dog (named Bailey). Using basically the same procedures as for Rico, the authors were able to show that Bailey could learn to accurately retrieve “randomly selected toys from a set of 117 on voice
command of the owner”. Furthermore, she could still perform the task with different human voices, one male and one female. The authors also showed that Bailey could perform exclusion tests: when a new object was placed among the objects of which she knew the names, she was able to bring back this new object on the request of a new name. But when the possible choice involved two different new objects, Bailey failed to answer properly, thus suggesting that her abilities were good in the exclusion learning task, but that she did not really “learn” the name of the object after a single presentation. The same objection could apply to Rico’s performance, since, according to the authors of the present article, Rico was not tested in an unambiguous situation, allowing to clearly reject a response by exclusion. Thus, according to the authors, the 2004 paper “was over-interpreted”. The present data emphasize the great intelligence of some dogs and their ability to understand many words. At the same time, they suggest that what has been interpreted in Rico’s behaviour as “fast mapping” might actually find other explanations. It should also be mentioned that fast mapping in human children still remains an open question. This important article, clearly presented and clearly discussed, though not closing the debate on how animals (and humans) learn, offers a very interesting and original point of view on animal intelligence.