This quote by William James from 1899 struck me as important:<p>> How little we actually hear, when we listen to speech, we realize when we go to a foreign theatre - for there what troubles us is not so much that we cannot understand what the actors say as that we cannot hear their words.<p>As a non-native speaker of English, I started watching English movies with subtitles when I was a teenager. This had an interesting effect: after a few years of doing this, I am now used to knowing each word that is spoken in a movie exactly, on its own - after all, it is clearly printed on the screen.<p>I now get nervous watching movies in my native language (German) without subtitles, simply because I am not able to extract each word precisely. Somehow I trained myself to expect an exact "acoustic" understanding from movies, as opposed to a "semantic" understanding. It is incredibly how the human brain is able to extract the meaning of a spoken sentence by context, facial expressions and gesture, even if we only understand half of the sentence acoustically.