creepy_rabbit said:
but we "normal" humans can learn many languages
Yes, but that's because we have grown up and our brain's development have adjusted to a specific mindset which makes the concept language learnable.
While dogs communicate with eachother, they don't really use a language for it in the sense that humans understand it. We have our own ways of conveying information to eachother, and this way that we call language has been developed to convey both basic information and very abstract information (something dogs do not engage in on the same advanced levels as humans).
Dogs communicating also use several other parts of their body than just their vocal chords and mouth like humans do. They wag their tails, they lift their ears, make several kinds of noises and also using their extremely advanced sense of smell.
A normal infant doesn't have a tail, nor will it ever develop the same advanced sense of smell that dogs have. So trying to make an infant "tune in" on how dogs communicate would be like trying to get a deaf, mute and partially blind person to completely understand human language. While a deaf, mute and partially blind person can certainly grasp the idea, there are aspects of human communication which these people will never be able to understand or express themselves with.
Try describing the colour red to a person that has been blind since birth, and you'll see the difficulties which im refering too.
Still, it is an interesting and mind boggling hypothesis though.