The prevailing wisdom seems to be that one of the best ways to get started learning a foreign language is to watch TV or movies in that language.  “If you just keep watching,” say many language wonks, then you’ll eventually start to “pick it up.”  This can’t be further from the truth.
Listening to entire conversations or plots in a foreign language, without having some significant language skills as a base, fails to provide an anchor for your learning.  The result is hearing a string of gibberish from which little or no actual learning takes place.  To achieve real learning, according to Krashen’s “Input Hypothesis”, the learner must be incrementally exposed to phrases that are just beyond her level of comprehension.  (Krashen defines this concept as k+ 1.)  This is the equivalent of hearing a sentence in which all words or grammatical concepts are familiar except for just one.
In other words, unless you are watching foreign language cartoons directed at 2 year-olds, chances are that your random TV sessions are not exposing you to the language nearly as incrementally as your brain needs it.