Baby videos

All of the studies I have seen on babies watching videos intended to teach them vocabulary show that babies essentially pick up nothing. This always seemed a little odd to me, I mean they are watching shouldn't they learn some of the new words?

I have spent most of the past year listening to Spanish radio when I drive. This was a combination of my car not working well to play MP3s and getting annoyed over all of the celebrity gossip and repeating the same five songs so much. In that year of Spanish radio I perhaps learned 10 words. Essentially nothing. Now it makes more sense how those babies don't manage to pick up much of anything.