In the 1930s and 1940s Germany, Italy and Spain dubbed British and US movies (i.e. replaced the English audio with that of their own language) to defend their national language and as a form of censorship to protect their regimes. It was also a problem of illiteracy as many people at that time would not have been able to read the subtitles. In Poland they initially used the same actor to dub every single part—male and female—of imported movies.
The first countries to introduce subtitles were Denmark and France, in 1929.
Dutch teenagers have a very wide vocabulary of everyday English because they tend to watch TV series—they thus hear the same expressions being said repeatedly over many episodes.