Children seem to drink in language, while learning a language as an adult seems to be quite a challenge.
That said, it’s not the case that you can’t learn anything about language just by listening. A number of studies over the last few decades have shown that even adults can learn a certain amount of word and grammatical structure just by listening to a speech stream for a few minutes. The current focus of research is determining what, exactly, is learnable and what is not.
A lab-mate is currently running one such study online. I mentioned it on this blog a couple weeks ago, but then there were technical difficulties with the experiment, and I pulled the post. Here it is again.
The study does take 20 minutes or more, and you have to promise to pay attention and not do other things at the same time (which I hope is the case whenever you do a Web-based study!), but it’s a good project and worth your donation time. When he has results ready to publish, I’ll be sure to post them here.
You can find the study here.